The newest, innovative, Top Check backwater valve designed to economically solve flooded basement and sewer backup problems.
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new top check backwater valves

top check backwater valves backwater check valves backwater valves adapt-a-valve information ml fr4 fio valve information termex valve information straight fit backwater valves backwater valve diagram backwater valve features and specifications backwater valve history testimonials backflow prevention information helpful links backwater valve pricing frequently asked questions backwater valve specifications backwater valve installation tips backwater valve animation backwater valve videos contact us backwater valves main page backwater valves backflow prevention links


Raw sewage in your basement.  Can you imagine it spewing out of your toilets, shower stalls and sinks?  With record high precipitation in many parts of the nation, some families have experienced such unfortunate events.  These backups not only cause damage that is difficult to repair, but also create dangerous health hazards.  A floor drain backwater valve or mainline ABS or PVC plastic backwater valve can save the day.  These check valves are also sometimes referred to as "backflow prevention valves" or "backflow preventer valves".

While cities and municipalities work relentlessly to clean and inspect sewer main lines, it is still possible for a sewer main to plug up and allow water and sewage to flow into the dwellings it serves.  But help is here!  By installing the award winning "Mainline Fullport Backwater Valve" (sometimes referred as a "Backflow Preventer") in the main line to the sewer, property owners reduce their exposure to such an incident to almost nothing.

positioning and placement of a sewer line backflow preventer valvesWho's at risk?  Your home or building may be susceptible to sewage backups if the lowest drain is less than 24" above the nearest upstream manhole.  Most building codes require owners to install a backflow prevention valve to minimize the chance of flooding at properties with drains that meet the specification mentioned above.

new top check backwater valves How does it work?  A backwater valve can be installed in the basement at the exit point from the home or building, or in the sewer lateral outside of the building. 

The "lateral" is the underground pipe that carries sewage from private property to the city’s sewer main.  The backflow valve is installed downstream and prevents sewage from backing up into the lateral beyond ("above in elevation") this valve.

backwater valve pricing    Detailed Backwater Valve information

access box for backflow valves
Access Box -
Model PE2013

(Access Box available with Top-Check Combo only)

When installing in a lateral, in some deeper installations the backwater valve can be placed in an access box to make maintenance easy.

Backflow prevention valves (and all safety check valves for that matter) should be inspected on a quarterly basis and anytime you think they have closed.  With our award-winning design, patented backflow valve, you can simply look through the clear plastic lid for easy visual inspection and remove the screw-off cap to clean out any debris!

Note: This type of check valve should not be confused with and does not replace the sewer trap that prevents sewer gas from entering a building where it is installed.

clear top of back water valve body
New Clear Top valve design
for easy visual inspection
(PVC valve shown)

Adapt a valve shown with DWV extender, flange, lid and extended removeable gate.

Mainline "Adapt-A-Valves" (shown at left "extended" with DWV from your local home center or supply house) in 3" and 4" PVC and ABS.

These valves are designed for indoor or outdoor use, but they are most economical when an in-the-ground installation is required because you don't need to pay for a costly vault to provide access.  (The mainline fullport backflow valve above is better for indoor use because you can visually see a problem with the clear top, but there are some indoor applications where an adapta-valve makes sense too.)

backwater valve adapt-a-valve pricing     Detailed Adapt-A-Valve information

The gate is designed a a removable cassette and is removed though a standard cap with a simple cut-to-length handle made from common 3/4" PVC pipe and a 3/4" PVC tee!

backflow check valve products



adobe acrobat pdf filesAdapt-A-Valve Brochure (Adobe Acrobat pdf)

Adapt-A-Valve Inspection Chamber

Backwater Valve Diagram
Backwater Valve Features
Back water valves information
Backflow Links
Backflow Preventers
Backwater Valve Animation
Backwater Valve Videos

Basement Drain Backing Up

 contact us about your backwater valve needsContact Us

Flood Alarm

Frequently Asked QuestionsBack water valve questions

adobe acrobat pdf filesFullport Backwater Valve Brochure (Adobe Acrobat pdf)

how to install your backwater valveINSTALLATION TIPS;  how to install backwater valves 

Termex Backwater Valves
Termex Backwater Valve Brochure (Adobe Acrobat pdf)

NEW: TOP-CHECK BACKWATER VALVESnew Top-check backwater valves

Mainline ML-FR4 Backwater Valve (Fio Valve)
adobe acrobat pdf filesML-FR4 Mainline Backwater Valve Fio Valve Brochure (Acrobat pdf)

6" Backwater Valves - Mainline STRAIGHT FIT Backwater Valves

Mainline History

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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telephone For non-order info, you may phone Greg at 330.836.9393 9 AM - 4 PM EST M-F
or Voicemail anytime)


copyright 2004 to 7/18/2024 at 18:25:54 ET,
Akron, OH, USA.
All rights reserved.

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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