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backwater valve and access box measurements

Classification: Type I – intended for use in horizontal pipe runs to floor drains, building drains, sewers, holding tanks, etc.

Application: Backwater valves should be used in building drainage systems whenever a risk of flooding due to sewer surcharge, back up, or failure exists.

. Backwater valves must be installed to ensure access for inspection or maintenance.
. Periodic inspection is important to maintain satisfactory performance of the backwater valve.
. The building owner must maintain and keep backwater valves in proper working order. 

Component: Body, Lid, Gate, Cleanout plug Acrylonitrile-Butadiene-Styrene ( ABS ) Plastic

Bolting System: Bolts - Stainless steel ¼ x ¾, Nuts - ¼ stainless steel

Gate Seal: Neoprene rubber ( Buna 50 durometer #241 )

Lid Gasket: Flat-section closed-cell gasket Neoprene 3/16 x 3/8 ( 1220 RL BL x 1 )

Floatation Devices: Closed-cell cross-linked polyethylene ( PEX ) foam “Boltaron Polyethylene”

Dimensions: Width: 10" (254 mm), Length: 15.5" (394 mm), Height: 11" ( 280 mm )

Certifications & Approvals:

(printable documentation - Adobe Acrobat .pdf)

All Valves (Adapt-A-Valves and Backwater Valves) in both ABS or PVC are Schedule 40.

ACCESS BOX DIMENSIONS: The overall width of the open base of the black PE 2013 Access Box is 14-7/8" X 20" and steps down to 11-1/8" X 14-7/8" at the top of its 16" height. The removable gray high density polyethylene (plastic) top access panel is 10-7/8" X 14-1/2". The access box top is held in place by two 1/4" Plastic Push Fasteners.

Additional Fullport Backwater Valve Specs


Additional Adapt-A-Valve Specs


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backwater valve measurements and specificationsMeasurements, Specifications and IAPMO Certifications


Mainline Fullport Backwater Valves offer the right solution for your sewer backup problems.

Protect Your Home with a Backwater Valve

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backflow prevention links is independently owned and resells products produced and manufactured by Mainline of Canada and assumes no liability for the installation of backwater valves and related products.

Be sure to check with the plumbing authority in the municipality in which your valve is to be installed to insure that your installation is in compliance with local code, and be sure have your valve inspected by your local plumbing inspector after installation. Inspect your valve frequently; the Backwater Valve through its clear plastic housing top, and the Adapt-A-Valve, by removing the gate cassette.


Pipe end-to-end, the Adapt-A-Valve takes up 6" of run in your line and the outlet is 1-1/2" LOWER than the inlet, so in just 6" the level of the pipe at the outlet side needs to be 1-1/2" lower.

Pipe end-to-end, the Backwater Valve takes up 12" of run in your line and the outlet is 3/4" LOWER than the inlet, so in just 12" the level of the pipe at the outlet side needs to be 3/4" lower.

Depending upon the amount of slope in your line (2% minimum is required for proper operation), you may need to replace several feet of pipe downstream from the valve to average out this "loss" of fall.

NOTE: New Straight-Fit and ML-FR4 require less slope. (refer to detail pages for these products)


Mainline Valve Warranty
(in printable Adobe Acrobat .pdf file)

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