Practices for collection and handling of drinking water samples

Overview

This guidance is for:

• drinking water system owners and operators
• anyone who may collect and submit a sample to a licensed drinking water testing laboratory in Ontario to meet regulatory and permission requirements
• provincial officers sampling to verify the integrity of a drinking water system’s self-monitoring information, or in response to adverse water quality notifications

Disclaimer

Although efforts were made to ensure the accuracy of the information in this guide, the Ministry of the Environment, Conservation and Parks does not assume liability for errors that may occur. The mention of trade names or commercial products is for explanatory purposes only and does not represent endorsement or recommendation for use by the ministry.

The sampling techniques may be used as guidance and as an example of best practices for treatment plant owners and operators sampling to meet Ontario’s environmental regulatory and approval requirements.

Laboratories are recommended to use this guide for the required information they need to provide to their samplers. Laboratories must also ensure that the information provided to samplers corresponds to the requirements of their analytical methods.

Introduction

The regulation of drinking water systems and drinking water testing under the Safe Drinking Water Act, 2002 (SDWA) helps ensure safe drinking water in Ontario. The SDWA and its associated regulations:

• govern the sampling and testing of drinking water at municipal and non-municipal drinking water systems
• requires that Ontario drinking water testing must be conducted by a licensed laboratory

These test results are used to evaluate the safety of drinking water and demonstrate compliance with the regulations.

Drinking water systems and regulations

Small drinking water systems that serve only public facilities like restaurants and hotels are jointly regulated under the Health Protection and Promotion Act (for treatment and sampling) and SDWA (for laboratory analysis and reporting adverse conditions).

This page provides general guidance for the collection and handling of all drinking water samples that fall under Ontario Regulation 170/03: Drinking Water Systems. This page can be used as a guide for systems regulated under Ontario Regulation 319/08: Small Drinking Water Systems, but it is recommended that systems consult with their local public health unit for any additional information. For information on the sampling points, procedures and frequency of sampling for schools and child care centres under Ontario Regulation 243/07: Schools, Private Schools and Child Care Centres, refer to flushing and sampling for lead.

Laboratory standards

Laboratories and drinking water systems should have their own standard operating procedures for the collection and handling of drinking water samples. Those procedures must incorporate best practices for ensuring the integrity of the sample. These procedures may incorporate information from this guide and should be referenced accordingly. Drinking water analytical methods can only produce accurate and reliable results when both the laboratory and field personnel use sample collection and handling best practices consistently.

Practices on this page are intended to supplement the quality assurance and control activities in laboratory testing. They provide a minimum level of quality assurance necessary to ensure that the samples tested reflect the quality of the water supply accurately.

The laboratory may also use these practices as their sample collection and handling directions. When used by the laboratory, the laboratory must ensure that:

• the information corresponds to the specific requirements of their licensed analytical methods
• their policies and procedures clearly reflect they have used this guide

Scope

This guidance is intended to apply only to grab samples that are collected and transported to a laboratory for analysis. Grab sampling methods are used to meet the requirements of the regulations unless otherwise specifically stated (refer to the sampling section for full definition. Operational checks of the treatment process, including continuous in-line monitoring for operational parameters are beyond the scope of this guide. In situations such as emergency and priority responses, it may be necessary for deviations from these guidelines depending on the circumstances. These situations are beyond the scope of this guidance and the laboratory should be contacted for specific sample collection and handling directions.

Representative samples and representative data

Sampling and analysis must be done in a way that produces data that are accurate and represent the quality of the water used in drinking water systems. A representative sample is an accurate reflection of the water source being sampled. The objective is to collect a sample that has the same characteristics and analyte concentrations as the water source. The location, time and method of sample collection are important aspects to collecting a representative result. These will be discussed in detail in the sampling section.

The sample must remain representative from collection until testing. Sample collection and handling procedures are necessary to ensure that:

• the integrity of the target analyte(s) is maintained
• the physical, chemical, and biological characteristics of the sample are not compromised

Temperature control and chemical preservation are the 2 most important ways to stabilize a sample. The time between sample collection and analysis must also be limited to minimize potential changes in analyte concentration.

Follow best practices for:

• recording sample and sampler information
• maintaining chain of custody
• sample labelling

Following these practices will ensure that the drinking water sample collected will be traceable from start to finish and accurately reflect its location, time and date of collection.

Sampling

Sample collection and handling in the field is the first step to ensure accurate and reliable results. This page provides general guidance to ensure an appropriate sample is collected.

Be aware of the conditions that the collected sample represents. Sampling points must be selected to address the intent of the regulations. Sampling at the same point at a given frequency can be useful to identify trends and monitor variability over time.

When selecting the time and location of sampling, consider the following:

• peak usage periods
• isolation of the effects of reservoir or storage
• dead ends in the system
• the extremities of the distribution system
• residential plumbing

The sample handler or analyst may incorporate additional quality assurance activities into sampling to improve the analytical data. In some cases, local conditions (geology, industry and more) will need additional sampling beyond the regulatory requirements. Additionally, an approval or order may also request sampling beyond the regulatory requirements to address specific concerns.

Sample type

Grab samples and composite samples are the two types of samples generally used.

Grab samples

Grab samples represent the characteristics of the water sampled at a specific time. If multiple containers or a series of samples are required, collect them within approximately 15 minutes or less from the time the first container is filled. Use grab sampling methods for the requirements of the regulations unless specifically stated otherwise.

Composite samples

Composite samples provide information on the average value in systems or processes that are highly variable over time. Composite samples are not used for regulatory drinking water testing and are outside of the scope of this guide.

Sampling location

Ontario Regulation 170/03 requires the collection and testing of raw, treated, distribution and plumbing water samples. Corrective actions in Schedules 17 and 18 to Ontario Regulation 170/03 have additional sample location requirements. The sampling locations must be carefully chosen to ensure a representative sample is collected. If sample location requirements are unclear, find more information by contacting the local ministry office.

Raw water

Raw water refers to the source water before any treatment. It is important to know the source of the water since its characterization is needed to determine the treatment requirements.

Consult Ontario Regulation 170/03 for raw water monitoring requirements for a drinking water system.

An engineering evaluation report (new or altered system) may require raw water characterization following all parameters listed in Ontario Regulation 169/03: Ontario Drinking Water Quality Standards and Ontario Regulation 170/03.

Sampling raw water

The raw water sample must be collected before any treatment process. This includes any pre-disinfection treatment processes such as aeration or oxidation and pre-chlorination. Raw water samples should be collected before the water enters any storage or pressure tank.

If samples are taken after storage units, the unit should be purged to allow a complete exchange of water. If samples are taken before a storage unit, taps located after the storage tank should be opened to prevent backflow. If it is necessary to turn off treatment equipment to obtain a raw water sample, the resulting untreated water must not be allowed to enter the distribution system.

Groundwater

Groundwater systems are drinking water systems that draw from groundwater sources such as a secure well or a groundwater under the influence well.

Sampling groundwater systems

For groundwater systems using more than one well supply, grab samples for microbiological testing are required from each production well.

If multiple wells are used and the water is blended at or before the high lift pumps, samples of the raw water must be taken from each well before the water is blended. If this is not possible, the system owner or operator must contact the ministry to obtain approval to use blended raw samples.

Samples should be collected from a tap located as close as possible to the well. Usually, a tap in the pump house is used. A continuously running tap that does not drain back into the well can also provide a representative raw water sample. If a tap is not available, it may be necessary to shut down the pump and open the sanitary seal.

Purging wells

The protocol for sample collection at wells sometimes requires purging the well to get a stable pH and turbidity measurement before sample collection. Purging is not required for wells in which the pump runs continually and where in-line plumbing is present. For these wells, flushing the lines for a minimum of 2 minutes prior to sample collection is enough.

Wells that are not currently used or that are used intermittently should be purged by flushing the lines with a volume of water equivalent to 3 to 5 times the volume of water standing in the well. The volume will depend on the static level and the inside diameter of the well casing. For pumps that are operated intermittently, the purge volume must be calculated with respect to length of use and the size of the storage or pressure tanks. If storage tanks are present, purge to ensure that the volume of water in the tank is completely exchanged.

Surface water systems

Surface water systems are drinking water systems that draw from surface waters such as lakes, rivers and streams.

Sampling surface water systems

It can be difficult to collect samples at an intake that are a great distance from shore. However, near shore samples are not recommended as they can be subject to increased turbidity, algal blooms and bacteria and do not accurately represent the water quality at the intake.

Systems with high, intermediate and low-level intakes in the water body can use different levels simultaneously as source water for treatment. The level(s) used may be different depending on the period of the year. For these reasons, samples are generally taken after non-chemical addition screening, pre-sedimentation, wet well storage and low lift pumping to the treatment facility. These samples will reflect any changes in source water quality from these activities but are not expected to greatly alter the quality of the water for the purpose of regulatory sampling.

At some locations it is necessary to pre-chlorinate at the intake for zebra mussel control. During certain months of the year, it may not be possible to sample unchlorinated raw water at these locations. To collect samples that have not received treatment, install a separate intake line with tap at the plant. If multiple surface source waters or surface sources are used, each raw water source should be sampled separately.

Treated water

Treated water refers to all water which has undergone one or more treatment processes and is ready to be distributed to users of the system. This includes treatments such as:

• chemically assisted filtration
• iron and manganese sequestering
• primary disinfection
• corrosion control
• softening and fluoridation

Sampling treated water

Treated water locations must be selected to represent the water after all treatment processes are complete. The sampling location:

• should be at the point of entry of the water to the distribution system
• must be after the disinfection and before the first consumer

In rare situations where disinfection is achieved in the first run of distribution pipe after the treatment facility, it is recommended that a sample line draw water from that point for the purpose of treated water sampling or otherwise as required in an approval, licence or permit issued by the ministry.

Distribution system water

The term distribution system refers to the entire network that delivers the treated water from the drinking water system to consumers. This includes:

• storage tanks
• reservoirs
• standpipes
• pumping stations
• pumps
• service pipes

Sampling treated water

The objective of distribution water testing is to measure the quality of water being supplied to the consumer. Sampling of the distribution system is mandatory under Ontario Regulations 170/03 and 319/08. Depending on the regulation and the population served, some systems may require multiple samples to be collected. The sampling locations should represent and cover the entire distribution system. As such, the sample locations should be far from where the water enters the distribution system unless otherwise stated in the regulation.

This should include locations where the degradation of water quality and disinfection residual are possible, and the formation of disinfection by-products is most likely. Potential sample locations in the distribution system should include:

• elevated storage tanks
• dead ends
• ageing water mains
• distribution loops
• points with the potential for cross connection or back flow
• extremities of the distribution system

Whenever possible, samples should be taken at dedicated sampling stations within the distribution system. Dedicated sampling stations allow for the collection of samples directly from the distribution system, avoiding any impacts caused by a building's plumbing. If samples are collected from buildings, then the preferable sampling points are taps located on a service pipe connected directly to the water main.

Samples must not be taken from:

• hot water taps
• after water softeners
• any other home-treatment devices

The lines should be flushed prior to sampling so that the water collected is representative of the distribution system. In general, this can be done by flushing the tap until the water reaches a constant temperature (usually between 2 and 5 minutes).

Samples must not be taken from localized plumbing problems such as:

• Line breaches or illegal connection to cisterns that allow the entry of untreated water into the system.
• Taps that are used infrequently as localized microbial growth and mineral crusts within the plumbing may affect the sample.
• Locations where water pressure is not constant. Changes in water pressure can break up and suspend biological growth and metal crusts from the walls of the lines.
• Leaking taps and taps where water tends to run down the side of the faucet.

Plumbing

The term plumbing refers to the pipes and fixtures that distribute water within a building. In general, plumbing is considered to begin at the property line where it is connects to the service pipe and distribution system. “Lead plumbing” is defined as plumbing and service pipes with a lead content greater than 8%. This is normally found only in areas constructed prior to the mid-1950s. Solder is the material used to connect pieces of plumbing. “Lead solder” means solder with a lead content greater than 0.2% and was permitted for use on drinking water lines prior to January 1, 1990. Flushing is used until water samples can be deemed representative of the distribution system. Sampling points for plumbing are specified within Ontario Regulation 170/03.

Sample containers

The laboratory provides direction for submitting samples. Samplers are expected to use the sampling container(s) provided by the laboratory. If the sampler has questions, the laboratory should be contacted for clarification. Samples collected using an improper container will be rejected by the laboratory.

Container type

Sampling containers are provided by the laboratory. The type of container required depends on the specific test. For example:

• A test for metals requires a plastic container.
• Most organic tests require glass.
• Microbiology tests require a sterilized container.
• Amber glass or opaque plastic containers are recommended for compounds that are light-sensitive. If this is not possible, the container should be wrapped in aluminum foil or stored in a light-proof case.

For other methods, such as volatile organic compounds (VOCs), the analysis is done directly from the sampling container. For these methods, the laboratory will require a specific type of vial with a Teflon^TM septum cap.

Sample volume

There are specific sample volume requirements based on the type of test and the requirements of the laboratory. For example, many organic tests require 1 L sample volumes.

Contact the laboratory for the specific sample containers for the tests requested.

Sample collection

The collection and handling of samples prevents external contamination. People collecting regulatory samples should be properly trained in sample collection and handling. This includes having clean hands and clothing and considering health and safety measures for the location and type of sample. This is important especially when handling chemical preservatives. Contact the laboratory for specific health and safety information.

Samplers should clean their hands before collecting a sample, disposable gloves may be worn. Care must be taken that the inside of the container and cap do not touch anything other than the atmosphere. If the inside of the sampling container is touched, it must be considered contaminated and cannot be used. While the sample is being taken, the exterior of the cap should be held in the sampler’s fingertips and held away from any potential sources of contamination.

The collection of drinking water grab samples is generally done from taps located at the sampling points. Sampling taps should be free of:

• aerators
• hose attachments
• strainers
• mixing type faucets

Typically, water bottle filling stations should not be used for sampling due to the design and inability to remove filters prior to sampling.

Cold water taps must be used. Water from hot water heaters is stored under conditions that are not representative of the water supplied by the drinking water system. In general, unprotected outdoor taps should be avoided.

The best method for collecting a grab sample is to collect it directly into the container provided by the laboratory. This eliminates the potential for sample contamination from any intermediate container or equipment. This is required for certain samples such as:

• VOCs
• per-and polyfluoroalkyl substances (PFAS)
• hydrocarbons
• oil and grease

There may be situations where it is not possible to collect the sample directly into the laboratory container, for example when taps do not have enough clearance from the floor. In these cases, it may be necessary to collect the sample in an intermediate vessel and then transfer the sample to the laboratory container. Information on types and pre-cleaning methods for intermediate vessels is provided in the intermediate sampling equipment section.

Refer to the sample preservation section for guidelines on samples that require preservation.

Certain tests may require additional sample collection for quality control purposes, such as:

• duplicate samples
• field blanks
• travel blanks

A field blank, typically provided by the laboratory, contains analyte-free water or an equivalent substance. At the sampling location, the sampler must:

1. Open the field blank bottle.
2. Transfer the water from the supplied container to the individual sample bottle.
3. Then close and label the bottle properly.

A travel blank is a sampling bottle containing analyte-free water that accompanies the samples to the laboratory without being opened during the process. The laboratory will specify:

• the bottles
• sampling instructions
• required sample volumes

Microbiological

Sample bottles for microbiological testing contain a dechlorinating agent to neutralize any chlorine that may be in the sample. The preservative is used for both chlorinated and non-chlorinated samples and will not affect samples that do not contain chlorine. Microbiology tests require containers that:

• are clean
• are sterile non-reactive
• have leak proof caps
• have non-toxic liners which are provided by the laboratory

These containers must remain closed until the time of sampling to prevent contamination. It is recommended that sample containers for microbiological testing have caps with tamper-proof seals. If the seal is broken, the bottle should be discarded.

When filling the bottle, the sampler should:

1. Hold the bottle near the base.
2. Open the cap and fill with the recommended amount for the container size. It is best practice to fill to the fill line on the bottle, where indicated, otherwise fill to the shoulder of the bottle.
3. Leave enough space in the bottle to allow for shaking before analysis.

To prevent further bacterial growth in the sample after it has been collected, the sample should be kept cool during storage and transportation to the laboratory but must not be frozen. Further details are provided in the sample storage and transportation section.

Organic compounds

Sample containers for organic compound analysis must never be rinsed with the sample, as the organic compounds from the rinse may accumulate on the container walls and compromise the test results. Sample containers should be filled slowly to prevent overflowing and bubble formation. Overflowing containers or bottles filled past the recommended volume for the container (for example, the sample bottle “fill line”) that are pre-charged with preservative can result in ineffective sample preservation and invalid results. If a pre-charged container overflows or is filled past the recommended volume for the container, it should not be used, and another sample should be collected into new pre-charged container.

Intermediate sampling equipment

Intermediate sampling equipment is generally not recommended. However, in rare situations the use of an intermediate sampling container may be necessary. In these situations, the laboratory should be contacted for direction on the suitability of the container. Usually, a glass or stainless-steel container is recommended. In general, the intermediate sampling containers should be cleaned with hot water, phosphate-free detergent, and thorough rinsing with analyte-free (for example, distilled) water. When sampling for organic compounds, additional solvent rinsing should be incorporated into the cleaning (the laboratory will advise on the choice of solvent). If funnels or tubing are required, Teflon^TM or stainless steel should be used, as they have low friction surfaces that do not readily adsorb contaminants from water.

It is recognized that pumps (for example, well pumps, high and low lift pumps) form an integral part of a water system. However, auxiliary sampling pumps should be avoided. They may contain brass, plastic, rubber and pump oil that can potentially contaminate samples. This is an important consideration for trace organic compounds and metals analysis. If auxiliary sampling pumps must be used, consult your laboratory for further instructions.

Sample filtering

Drinking water samples shall not be filtered in the field. Where the protection of analytical instrumentation is necessary and where detailed in a licensed method, the laboratory may be permitted to filter the sample prior to analysis. It is not expected that consumers filter their water before drinking. Unfiltered samples will be more representative of what the consumer is drinking.

Filtered metals results may be used for investigative purposes but may not be used for regulatory compliance.

Sample preservation

Chemical preservation may be required to stabilize the analyte in the sample from the time of collection until the analysis. This may prevent increases or decreases to the analyte concentration after sample collection.

The specific preservative depends on the target analyte and testing method and is provided by the laboratory. Preservatives are not interchangeable. It is critical to follow the specific sample preservation requirements of the laboratory. Contact the laboratory for information and instructions on the specific preservatives.

Containers that have been pre-charged with preservative must not be rinsed, filled to overflow during collection, or be filled past the recommended volume of the container. If this happens, the preservative will be diluted and may not be effective. As such, those samples should be discarded, and a new one collected. Additionally, preservative is not to be removed prior to sampling.

In some instances, bottles will not have pre-charged preservatives. The sampler will be expected to add the preservatives at the time of sampling. The sampler must use preservatives that have not expired.

The 2 main types of chemical preservation for drinking water samples are dechlorination and pH control.

Dechlorination

Some analytes may be affected by residual chlorine. These require a dechlorination preservative or quencher to neutralize the residual chlorine. This is necessary to ensure the test results are representative of the water at the time of sample collection. There are different types of preservatives for this purpose depending on the laboratory and the testing method. Sodium thiosulphate is the most common preservative of this type. It is frequently used for both microbiological and organic analytes. Dechlorination preservatives must be either pre-charged in the bottle or vial or added to the sample at the time of collection.

pH control

Some analytes must be stabilized under acidic or basic conditions. For example, nitric acid is used for pH adjustment for metals testing. This improves the solubility of metals to maintain representative results.

When strong acid or alkali is used to preserve a sample collected in a plastic sampling container, it is recommended that the preservative be added after taking the sample. However, the use of pre-charged sample bottles from the laboratory is permitted where appropriate.

When preservatives are added to obtain a specific pH range, the sample should be swirled gently and left to equilibrate for 2 minutes. The pH should be checked with pH paper to ensure that the desired pH is reached. Different types of waters have different capacities for buffering (resisting a change in pH). It is recommended that the volume of preservative not exceed 1% of the sample. If this occurs, a note to this effect should be made on the sampling container label and the chain of custody.

Sample holding times

Holding time is defined as the time between the collection of the sample and the start of the analysis. For certain tests, the sample must be received at the laboratory and analyzed within a short period of time. For example, microbiological analysis must be started within 48 hours of sample collection. Consult the laboratory for specific holding time requirements. Timely test results are important so that adverse conditions can be addressed as soon as possible. Therefore, holding times must not exceed 60 days, even if the target analyte is known to be stable for longer.

Preservation can stabilize a sample to some extent but may not prevent all possible reactions or changes that could compromise the sample. Consequently, samples must be kept cool and delivered to the laboratory as soon as possible after collection. This will help to ensure that samples are analyzed within the required time frames.

Sample labelling

Samples should be accurately and completely labelled to maintain the identity of the sample. This is very important for sample tracking and interpretation of the test results. Sample identification is mandatory for data reporting and adverse water quality notification requirements under the legislation.

Pre-label all sample containers prior to taking the sample or label each container immediately after the sample is taken to prevent mislabeling. It is acceptable to use pre-printed electronically generated labels or labels completed at the time of sampling with a permanent marker or pen. The laboratory conducting the analysis will supply the sampling container and it may have a label already affixed to the container. Labels should be able to withstand water.

Laboratories require the use of a unique sample ID number or code for all samples. If the ID number or code is not assigned by the laboratory, it may be necessary for the sampler to create a sample ID number or code in the field. The sample ID number or code generated should be unique to the sampling set or batch collected.

The following information should be recorded on either the sample label or on an accompanying chain of custody form:

• marking to indicate that this is a regulated drinking water sample (where applicable)
• sample type: raw, treated, distribution or plumbing
• unique sample identifier
• legal name of the water system (available in the Ministry of the Environment, Conservation and Park’s Drinking Water Information System and the Ministry of Health’s Laboratory Results Management Application)
• waterworks number (where applicable)
• date and time of sample collection (critical for perishable tests)
• street address if the sample is a distribution sample. If no street address is available, enough information to uniquely identify the sampling point
• preservative(s) used if applicable
• pertinent field measurements (chlorine residual, turbidity, pH) (if room on the label/tag permits)
• initials of the sampler (and in the case of provincial officers, their sampler ID number)

Most of this information can be put on the labels or tags in advance of sampling, either by the laboratory or the sampler.

Pre-printed labels are convenient and provide the necessary information for the lab analyst as well as help prevent errors. Include:

• the drinking water system name
• number
• sample type and more

Easily identified sample information by the laboratory helps with prompt analysis and reporting.

Sample storage and transportation

The laboratory will provide specific instructions for sample delivery to the laboratory and on drop off depots if they are used.

It is recommended that samples:

• be delivered to the laboratory as soon as possible after sampling
• be kept cool or refrigerated, but not frozen if immediate shipping is not possible
• are packaged to avoid breakage during shipping
• are shipped in sealed containers to provide evidence of tampering
• are shipped with the chain of custody form - the sampler should keep a record of shipping, including the time, date, carrier, and any tracking numbers

Samples for microbiological testing should:

• be packed with ice packs or a suitable leak-proof container of ice and shipped in insulated boxes/coolers
  • packing the sample with loose ice is not recommended as it may contaminate the sample
• be less than 10°C before packing and during transport for optimal temperature conditions are
• be kept cool during transport if the temperature of the sample at the time of collection is above 10°C
• not freeze during shipment

Samples must be shipped to arrive at the laboratory with enough time for analysis before the holding time expires.

Chain of custody

A sample needs to be traceable from the time of collection through to its analysis to produce reliable results.

For drinking water samples, a chain of custody form must accompany samples to the point of receipt by the laboratory. The intent of this form is to document the transfer of custody of the samples from the sampler to the laboratory. The form can be obtained from the laboratory or can be self-generated by the sampler but must be approved for use by the laboratory. Contact the laboratory for their most recent form. Chain of custody forms, whether electronic or hardcopy, are required to:

• be secure
• be traceable as to the origin of the sample
• have a unique identifier for the form

For mandatory fields and more information, please visit the chain of custody forms section.

Specialized sampling techniques

Volatile organic compounds

VOCs quickly vaporize from the sample. For this reason, sample containers are vials with a Teflon^TM lined screw cap with a hole and Teflon^TM-lined silicone septum. This type of vial can be placed directly in the auto-sampler of the analytical instrument.

Avoid exposure of VOC samples to any type of solvent:

• Do not label sample bottles with markers before or during sampling.
• Avoid being in an area with known high VOCs on a day when VOC sampling will take place.
• Collect VOC samples prior to samples being collected in solvent rinsed bottles.
• During transportation, do not store VOC bottles with other bottle types that have been solvent rinsed.

Samples should be collected at least in duplicate and some laboratories may require triplicate. Some laboratories may also recommend the use of a field or travel blank. The laboratory will provide suitable vials and direction on the collection of duplicates, triplicates and the use of field or travel blanks.

When sampling for VOCs:

• The water should be run slowly to prevent turbulence or splashing.
• The vials or bottles should be filled slowly to the top rim of the container so that a meniscus (bubble of liquid that sits slightly over the top of the vial without spilling) is present.
• When capped, the cap (also called a septum) should be in contact with the sample so that no air is trapped in the sample container. A slight loss of sample may occur when the cap is applied.
• No air bubbles should be present when the vial is turned upside down.
• The Teflon^TM liner, not the silicone or rubber backing of the septum, must be in contact with the sample.

There are different preservative requirements for chlorinated and non-chlorinated water. It is important to use the vial pre-charged with the correct preservative. Contact the laboratory for specific preservative requirements for chlorinated and non-chlorinated samples.

Chlorinated water

Chlorinated water requires a dechlorination preservative. This stops potential reactions with residual chlorine and keeps the sample representative of the water at the collection time. The vials may be pre-charged with a dechlorination preservative.

Non-chlorinated water

For raw water or non-chlorinated water, a dechlorination preservative is not required. However, an alternate preservative may be used to halt bacterial activity. Vials may be pre-charged with a preservative such as sodium bisulfate which will lower the pH and halt bacterial activity.

Chlorate or chlorite

Owners and operators of municipal residential drinking water systems must test for chlorite and chlorate when chlorine dioxide is used as a disinfectant and sampling is required by their Municipal Drinking Water Licence. Owners and operators of non-municipal residential drinking water systems that use chlorine dioxide may need to test for chlorite and chlorate.

Drinking water systems not using chlorine dioxide treatment

If samples are required or taken voluntarily by the owner, they must be preserved with Ethylenediamine at the time of sample collection, but sparging (bubbling) is not required. Submit the samples to the laboratory as soon as possible to ensure that laboratory holding time requirements are met.

Drinking water systems using chlorine dioxide treatment

To sample for chlorite and chlorate, contact your lab for detailed instructions. The following are general steps that are often followed when sampling for chlorite and chlorate:

1. Samples should be sparged (bubbled) at the time of collection with an inert gas (such as helium, argon, nitrogen) for approximately 5 to 10 minutes. Otherwise, residual chlorine dioxide will continue to form chlorite and elevate the results.
2. Add Ethylenediamine immediately after sparging. Ethylenediamine preservation for chlorite will also preserve the integrity of chlorate, which can increase in unpreserved samples as a result of chlorite degradation.
3. Place chlorite and chlorate samples in plastic or amber glass bottles and store in the dark at 5°C ± 3°C.
4. Submit the samples to the laboratory as soon as possible to meet laboratory holding-time requirements.

How to sparge (bubble) a water sample:

1. Collect the water sample in a wide-mouth container. Make sure that the inside of the container does not come into contact with anything other than the water sample.
2. Connect a tube to the inert gas cylinder and insert a new glass pipette at the other end of the tube. Insert the other end of the pipette into the container so the open end is in the water, but not touching the sides or bottom of the container.
3. Slowly open the inert gas and bubble the water sample gently and steadily for 5 to 10 minutes.
4. Remove the pipette and turn off the gas. Transfer the water sample to the pre-charged Ethylenediamine container.

Drinking water sample requirements

Table 1 outlines commonly sampled drinking water parameters:

• the type of container
• volume
• preservative
• holding time
• storage conditions

Note: Contact your drinking water testing laboratory for specific sample handling instructions as there may be some variations in conditions.

For this table, Cool means storage at the laboratory at any temperature range between > 0°C (above freezing point of water) and ≤ 8°C. For example, 5 ± 3°C; 4 ± 3°C; or > 0°C (above freezing point of water) to ≤ 6°C, would all be acceptable temperature ranges.

Related

• Protocol of accepted drinking water testing methods
• Community sampling and testing for lead
• List of licensed laboratories
• Drinking water testing requirements for laboratories
• Required qualifications to operate, test or sample drinking water systems
• Ontario Regulation 248/03: Drinking Water Testing Services