Overview & Design


How it Works

The Mainline Fullport Backwater Valve Model #4963 was developed to fill a need for better, and easier, backflow protection for both the installer and building owner.

Until recently most plumbing codes did not allow a backwater valve to be installed on a main-building drain. Municipal sewers exert both negative and positive air pressures, and a building venting system alleviates these pressure differences. Free circulation of air between a municipal sewer and a buildings venting system is essential for the proper flow of sewage. The only backwater valves available when the codes were originally written, were the "normally closed" design and these valves would not allow a free circulation of air between the building and municipal sewer.

The Mainline Fullport Backwater Valve features a 'normally open' gate design which makes the free circulation possible. The valve allows the free flow of air to vent through it, and at the same time in the event of a sewer back up, the gate floats into the closed position to protect the building from backflow.

Because of this normally-open technology, Special Changes to the National Plumbing Code of Canada were made to allow for main-building drain protection versus the old standard which restricted backwater valves to the branch line of the building drain only. Today, the plumbing industry has embraced this method of backflow protection and the Mainline Fullport Backwater Valve. Home Why a Mainline Valve How it Works Installation Links Contact Us Privacy Policy Mainline Backflow Products Canadian Home Builders' Association Mechanical Contractors Association of Alberta

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