Wells Regulation – Flowing Wells (technical bulletin)
This is technical bulletin 1 of 11 on well issues created for a person who is considering a new water supply well or who currently owns a water supply well.
The purpose of this technical bulletin is to summarize the information on flowing wells found in the Water Supply Wells Requirements and Best Management Practices manual published by the Ministry of the Environment and Climate Change.
Flowing wells occur when water pressure in an aquifer causes the water level to rise above the ground surface. In many cases, if uncontrolled, the water will flow out of the top of the well. A flowing well is a type of artesian well.
There are several things that are important to know with respect to flowing wells:
- There are specialized construction techniques and devices that are used when constructing a well in flowing conditions to control the free flow of groundwater from the well.
- Improper construction can lower the aquifer’s hydraulic pressure, waste groundwater, cause interference with other wells and create flooding problems.
- Elevation and a confining layer are some factors that can create conditions for the development of a flowing well.
- Precipitation infiltration into and pumping out of the same aquifer may cause the groundwater levels to fluctuate, which may lead to intermittent flowing conditions.
It is essential to control flowing wells to:
- conserve groundwater resources,
- prevent adverse effects such as property damage, flooding, sediment deposition, erosion and surface water impacts,
- preserve the pressure within the aquifer, and
- prevent the creation of a direct pathway for contaminants.
To address these concerns, Regulation 903 (Wells Regulation), as amended, made under the Ontario Water Resources Act provides minimum construction requirements for the construction of a flowing well.
Best management practice - Planning to control the flow
Prior to construction in an area known to have flowing well conditions, it is essential that a plan be in place to control the flow of groundwater from the well.
The person constructing the well should consider retaining a Professional Geoscientist or Professional Engineer (consultant) experienced in the design of wells in flowing well conditions. If the person constructing the well is unfamiliar with the area or with flowing well conditions, it is important that a licensed well technician who works for a licensed well contractor and who is experienced with flowing wells be consulted. In some cases, installing a test hole may be appropriate to determine subsurface conditions.
Figure 1: Geological Conditions that Create Flowing Wells
There are three wells that have been constructed into the subsurface.
The well on the left has been constructed through a sand and gravel subsurface material. There is a confining layer (for example clay or silt) below the sand or gravel subsurface material. As a result, water from precipitation will migrate down through the sand and gravel from the ground surface and collect in the sand and gravel forming an aquifer. The top of the aquifer is called the potentiometric surface (or water table).
The well on the left is a shallow well that has been completed just below the potentiometric surface (also known as the water table). As there is no pressure exerted by a confining material on top of the sand and gravel, the water level in the well is exactly the same as the potentiometric surface (or water table). This type of well (on the left) is called a water table well.
The well in the centre has been constructed through a confining layer (for example, clay or silt) and into the sand and gravel subsurface material that contains the aquifer. The weight of the upper confining layer exerts a positive pressure on the water aquifer in the subsurface. When the well in the centre is constructed through the confining layer into the aquifer, the positive water pressure is released causing the water to rise up the hole until the water level reaches the same pressure as the atmosphere. As the water level is above the actual level of the aquifer, the potentiometric surface (water table) is shown to be above the actual location of the aquifer at and around the well in the centre. This type of well (in the centre) is called an artesian well.
The well on the right has been constructed in a similar fashion as the well in the centre; however, the ground surface at the well on the right is at a significantly lower elevation than the well in the centre. As positive pressure in the aquifer is the same in both wells, the potentiometric surface (or water table) is actually above the ground surface at the location of the well on the right. When the water level rises in the well on the right to achieve an equal pressure with the atmosphere, the water pressure causes the water to flow out of the well onto the ground surface. This type of well (on the right) is called a "flowing well".
Construction and device requirements
If the well becomes a flowing well during well construction, the Wells Regulation specifies that the person constructing the well must meet the following requirements.
The well must be constructed to accommodate and be compatible with a device installed on or in the well that:
- controls the discharge of water from within the well casing,
- is capable of stopping the discharge of water from within the well casing, and
- is capable of withstanding the freezing of water in the well casing.
Further information on types of devices is provided in Chapter 12: Flowing Wells of the Water Supply Wells Requirements and Best Management Practices manual.
The construction of the well and the device installed must prevent any uncontrolled flow of water from the well or at the well site. This device must prevent the backflow of water and other material into the well.
For clarification, the proper control of discharge water from a flowing well consists of:
- controlling, and if necessary, stopping the discharge of water from within the well casing,
- preventing the discharge of water from around the casing by tightly sealing the space between the hole wall and the well casing (annular space) and in some cases between two well casings if there are multiple casings, and
- preventing groundwater originating near the well from discharging at the surface some distance away from the well.
Abandonment option
If the flowing well cannot be controlled as required by the Wells Regulation, the only option is to abandon the well, according to the Wells Regulation. For further information on abandonment of a well see the technical bulletins titled Wells Regulation Well Abandonment: When to Plug & Seal a Well and Wells Regulation Well Abandonment: How to Plug & Seal a Well.
Costs
It is a term of every contract between the well purchaser and the well contractor for the construction of a well that the well contractor is responsible for the costs of:
- complying with the above requirements for controlling a flowing well, and
- abandoning the flowing well, if applicable.
This is the case irrespective of whether the contract is written or verbal or whether this responsibility is explicitly written into the contract or not. The only exception is if there is a written contract between the well contractor and well purchaser that specifically releases the well contractor from these costs.
Venting
If a pump is installed in a new or existing flowing drilled well, an air vent must be installed on the upper end of the casing that allows for an equalization of pressure between the inside of the well casing and the atmosphere. The vent must also allow for the release of all gases from the well. The air vent must meet the minimum size, length and shielding requirements found in the Wells Regulation (see Chapter 9: Equipment Installation of the Water Supply Wells Requirements and Best Management Practices manual for more information).
Venting exemption
A new well, in which the casing is used to transmit water out of the well (e.g. flowing well) without a well pump, does not need an air vent.
Chlorination exemption
The Wells Regulation disinfection requirements do not apply to flowing wells. For a best management practice on disinfecting flowing wells, see Chapter 8: Well Disinfection of the Water Supply Wells Requirements and Best Management Practices manual.
Approvals
A Permit to Take Water under the Ontario Water Resources Act may be required when the flow of groundwater freely discharges from a well at a rate that is greater than 50,000 litres (11,000 Imperial gallons) on any one day. Therefore, it is important that the person constructing the well estimate the taking before constructing the well. If the estimate shows the flow rate will exceed 50,000 litres on any one day, then the person constructing the well needs to obtain a Permit To Take Water from the Ministry of the Environment. Find more information on Permits to Take Water.
Other discharge approvals issued by the Ministry of the Environment under the Ontario Water Resources Act may be necessary if the groundwater from the flowing well discharges into other waters such as a lake, creek or river.
It is important to design, construct and regulate a flowing well properly by obtaining the necessary approvals which protect the environment. If the required approvals are not obtained, the person is out of compliance.
Additional information sources
This technical bulletin on well issues is one in a series of 11 created for owners of water supply wells which are available on the Water Supply wells: technical bulletin page.
Further information on flowing wells for water supply wells can be found in Chapter 12: Flowing Wells of the Water Supply Wells Requirements and Best Management Practices manual.
A copy of the Water Supply Wells Requirements and Best Management Practices manual can be obtained from the ministry’s website.
For all of the requirements on non water supply wells (e.g. test holes or dewatering wells) see the Wells Regulation.
A copy of Regulation 903 (Wells Regulation), as amended, made under the Ontario Water Resources Act and other regulations can be obtained from the e-Laws website.
The publications are also available by calling the Publications Information Centre at
For further information about wells, contact the Wells Help Desk at
Notice: This bulletin is being provided for information purposes only and is not intended, nor should it be construed as providing legal advice in any circumstances. The applicable legislation including the Ontario Water Resources Act and Regulation 903, as amended and made under that Act, should be consulted. Legislation and regulations change from time to time so it is essential that the most current versions be used.
PIBS 8185e