Backwater valve installation to protect and prevent basement flooding

Different types of backwater valves to protect diffrent plumbing fixtures in the basement against city sewer bakflow

A backwater valve is a device that prevents the municipal wastewater from backflowing into the basement. The flap closes automatically when the sewage is forced back. A properly installed backwater valve must be located in such a way that the discharge is blocked and there is no opening in the basement, such as sinks, toilets, showers and laundry tubs.

To ensure that the backwater valve is compliant and properly installed, the work should be done by a plumbing contractor. All backwater valves must be placed in such a way as to be accessible. An access door or a removable panel must be provided when it is located inside a wall, ceiling or false floor.

Synonyms: Anti-return valve, check valve, backflow prevention valve.

There are three different types of Backwater Valves
  • Normally opened backwater valve
  • Normally closed backwater valve
  • The Squeeze-in


The Normally openened backwater valve

A normally opened bakwater valve in the type of backwater valve to install on a main serwer pipe to prevent city serwer backflow and basement flooding

The flap of this device is normally opened. The air in the plumbing network can therefore pass unobstructed, as well as the waste water from the protected building. When the sewage is backed up, the valve is lifted to close the passage to the backflowing water preventing it from going further into the building. It should be noted that the installation of a Normally opened backwater valve on a sanitary collector is permitted only if it serves a single-family home and that this home is sheltered by a sloped roof, not a flat roof.

The Normally closed backwater valve

A normally closed backwater valve is the type of backwater valve to install on secondary drain pipes to prevent city sewer backflow and basement flooding

The flap of this device is in the closed position in normal time. When sewage is discharged into the sewer, the flap opens up to allow it to pass. However, if the sewer backflows from the city to the building, the pressurized water will abut the flap in the closed position.

The main disadvantage of this valve is that it does not allow the air to circulate in the network and therefore it can not be installed on a main collector which must allow ventilation of the sewer.

The Squeeze-in backwater valve

The sqeeze-in type of backwater valve is a type of backwater valve that can be installed in floor drains to prevent city sewer backflow and basement flooding

Commonly called “squeeze-in”, this backwater valve is specifically designed to be installed in a floor drain. It is installed by removing the grid from the floor drain and inserting it into the pipe. It is held in place by compressing a rubber ring with two brass plates connected together by bolts. The grid of the floor drain is then replaced. Although the building code does not prohibit its use, it should be noted that some municipalities do not accept it. Therefore, you must first check with the municipality where the work is carried out before installing it.

The advantages of installing a Backwater valve with CHRONOS
  • Full service

Our service is complete: protection of the floors where the workers circulate, installation of a backwater valve and job area cleanup.

  • Up to code

Our installations are carried out in accordance with the National Building Code (NBC) and the specific municipal regulations.

  • Liability insurance

We are a member of the Corporation des Maitres Mécaniciens en Tuyauterie du Québec (CMMTQ) and the Régie du Bâtiment du Québec (RBQ). Our liability insurance is $ 1,000,000.

  • Customer service

We teach you the basics of operation and maintenance of your new backwater valve. We do a follow-up one week after the work is done to make sure everything is working normally and to answer your questions.

Backwater valve: Insurance companies and municipalities

In a plumbing system, it is mandatory to properly protect the plumbing fixtures against the potential backflow of sewers. In fact, the backflow of sewage and rainwater is the leading cause of water damage inside buildings and is one of the most frequent causes of complaint with the home insurance companies.

However, since 2006, municipalities have been able to avoid liability for damages caused to a residence or its contents during a sewer backup. How? By making it mandatory to install backwater valves by regulation. The owner of an building then has a minimum period of one year to make their building compliant. As for insurers, some will require an owner to install a backwater valve on their building to continue to provide coverage.

Annual inspection and maintenance of your backwater valve:

At least once a year, maintenance must be carried out to ensure that no debris has been lodged behind the flap or it’s hinge, thereby impairing the functioning or sealing of the backwater valve. The Corporation des Maîtres Mécanicien en Tuyauterie du Québec  advises to carry out this maintenance before spring or at the beginning of the summer period.

Procedure for backwater valves
  • Remove the screwed or bolted access cover or cap. (Note: if it is a cast iron backwater valve with a bolted lid, it is best to have the work done by a plumbing contractor).
  • Remove the flap to clean and check the condition of the rubber seal; Replace door if necessary.
  • Clean the hinge; It must be free of debris so as not to interfere with the operation of the valve.
  • Check for debris upstream of the flap. Clean as needed.
  • Reinstall the flap in the correct direction, ensuring that there are no obstructions to prevent it from pivoting.
  • Re-seal or re-attach the access cover or cap securely or replace it if necessary.

Basement flooding can be prevented by the installation of a backwater valve

Plumbing plumber CAA Recommended Aproved


CLICK 514-699-0006