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Drain Guard Sewage Backflow Preventer 3 in. and 4 in. Backwater Valve - Holmes Approved

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Product Overview

The Sentinel Drain Guard is a backwater prevention valve that is inexpensive and easy to install in just 1-step. Installed in your basement floor drain, it guards against sewage backflow entering your house. Using patented technology, the Sentinel has several auxiliary features to prevent failure in the case of backflow. Designed in Canada, CSA certified and the only sewer backwater valve on the market approved by Mike Holmes and the Holmes Group through their Make It Right initiative, the Sentinel drain guard is something every urban homeowner with a basement should have.
  • Sentinel is the only consumer backwater valve on the market that is a Holmes approved product
  • Fits 3 in. (75 mm) floor drain and 4 in. (100 mm) floor drain with included adapter
  • Sits in an open position so normal drainage can occur device will close in the event of a backflow occurrence
  • Unlike most backflow preventers, Sentinel comes complete with a fitted drain cover
  • Easy installation in a manner of minutes
  • High quality

Info & Guides

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Inlet Diameter (In.)
Outlet Diameter (In.)
Product Depth (in.)
4 in
Product Height (in.)
5 in
Product Length (in.)
5 in
Product Width (in.)
5 in


Compatible Pipe Material
Not Applicable
With Screws
No Additional Special Features
Maximum Pressure (psi)
Maximum Working Temperature (F)
Pack Size
Product Weight (lb.)
.07 lb
Valve Type
Backflow Prevention

Warranty / Certifications

Manufacturer Warranty
30 Day Warranty

Questions & Answers

Typical questions asked about products:

  • Is the product durable?
  • Is the product easy to use?
  • What are the dimensions of the product?

Customer Reviews

  • 3.8
    out of 15 reviews
  • 80% recommend this product
Filter by:
Showing 1-10 of 15 reviews
This is a really great invention. It was super easy to install and solved my issue of sewage coming back up my drain. I have laid my drain pipes on it and secured them so it's the perfect solution.
    Drain guard tidy
    Clean and tidy looking. I don’t know how well it works as we have had no backups yet
    • Verified Purchase
      Perfect solution
      Very easy to install and stopped our backflow issue.
        • Recommended
        The worst delivery experience ever.
        I am unable to comment one way or another on the product but the online order and curbside delivery was a nightmare. Home Depot needs to review their entire process. Would I use them again, not a chance.
        • Verified Purchase
        Peace of Mind Prevention
        Does the job and is peace of mind protection. Can't believe I didn't install this years before.
        • Verified Purchase
        • Recommended
        Drain guard backflo preventer
        Instructions are terrible. I can’t get it to seal tight enough. I can pull the middle section out of the drain when installed. Made of plastic with ping pong ball as the stopper. (No kidding) I’m not a fan of this design and it didn’t work for me.
        • Verified Purchase
        Cost effective, easy to install
        Recently purchased to insure against backflow of waste or storm water into our basement. This is an ingenious product that has been designed to cost-effectively solve a problem with minimum fuss.
          • Recommended
          Great idea, poor quality materials
          I purchased the SENTINEL 3"/4" Back-flow Floor Drain Valve back-flow valve to replace a 12 year old traditonal design 3" Back-flow Floor Drain Valve that had rusted. The design and use of plastic is great and it can be used for 3’ and 4” drains and comes with a cover… all great ideas. HOWEVER, there is no way it can be effectively installed because the four screws used to tighten it to the drain are self-tapping and go into the black plastic material it is made out of and I can guarantee, you will strip it if you tighten them sufficiently. This means almost any amount of pressure from below would dislodge the whole unit, defeating it’s purpose. While the alternative Moen product will rust and the rubber will eventually perish a little, the screws go into to steel to tighten it and the screws do not rust as they are made of stainless steel. You may have to replace it is every 10 years or so, but it works and is easy to remove and replace. Finally, the SENTINEL 3"/4" Back-flow Floor Drain Valve is endorsed by Mike Holmes and as I find with many products he endorses, the idea is great, however the materials and production quality make the product questionable. Save some money and buy the traditional valve.
            Well made!
            Easy to use and fits well. It is well made and good quality.
              • Recommended
              Showing 1-10 of 15 reviews