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Backflow Preventer Valves

Using MAINLINE BACKFLOW PROTECTION, a backwater valve is installed where the sewer exits the building on the main-building drain. There are several benefits and advantages of putting a backwater valve on the main-building drain:

  • Only one backwater valve is required for the entire building.
  • The entire building is protected from backflow.
  • It is conveniently located where the main-sewer cleanout is.
  • It is easy to locate and access.


The Mainline Fullport Backwater Valve is installed in the main-building drain, because its fullport design allows venting of the municipal sewer through the building. The design also allows unobstructed sewage flow and automatic closure of the gate upon reversal of flow (sewer backup) protecting the entire building from backflow.

  • The entire plumbing system is protected from municipal sewer backup with just one conveniently located backwater valve at the point where the building drainsewer exits the building. This offers EASY HOMEOWNER ACCESS
  • The Mainline Fullport Backwater Valve has a built-in main sewer cleanout in the valve for the rodding of the sewer.
  • Since the Mainline Fullport backwater Valve is a “normally open” backwater valve, it allows unobstructed sewage flow, which in turn prevents sewage buildup in the valve’s body.
  • The “normally open” design allows cleaning tools to pass through the body without getting hooked on the gate when retrieving the cable (this prevents the gate from being destroyed).
  • By installing the valve in the main-building drain it eliminates the need for branch line backwater valves, cleanout assemblies, and also saves in groundwork labor and extra piping when, trying to utilize one branch line bwv to protect extra fixture drains.
  • Ensures that entire building is protected from backflow, where branches are often missed and left unprotected, when using branch line protection.
  • If additional fixtures or branches are added to the system they are automatically protected from backflow.

mainline diagrambackflow valve diagram

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