Internal Backwater Valve,4-F 4" Float Model Flood-Guard for 4-inch Flood Drains,Drain Backflow Preventer for Sewer Flood Protection

A+. I deal with basement back ups when the city streets flood. Sump pump is fine, storm sewer is issue a backflow valve in the yard would cost thousands to install. This worked great so far in my basement. Last time I would’ve had an issue it barely let any water seal past the gasket edges. Usually I’d have 2-4” in the basement under these circumstances. I can probably tighten it a little more again, but it was very tight to begin with. Hold it with 1 hand and start screwing the 4 screws in a circle. Once snug you can crank it tight. Lean edges as best as possible. Mine was cast iron so hard to clean. Fit well. Works well. Also best one I’ve seen to allow water to go in, and not clog it up.

This is excellent. I replaced one that I had for years but corroded. The key to using these is to put it down into the PVC tube just far enough that the center "pin" sticking up is about 1/4 inch below the level of the floor. This is made well, is a quality item, and is easy to install. I may buy another one so that in 20 years when this one is all nasty, I can replace it easily.

The 2" model is a much poorer design than the others. Because it uses only 2 screws instead of 4 it is very easy to accidently get the rubber O-Ring misaligned and then you have to start the whole process over again. Be very careful when inserting this and tightening it to get it perfectly straight in the drain!It comes fully tightened and will not fit in your drain in this config. You need to almost fully loosen the two side screws. The O ring will then get sucked a bit into the sides of the device.The main problem however is that the spring is simply WAY too strong. I suspect they used the same spring and design from the larger models which would have much more water on top compressing it down. To make this work you will need to:1. Cut a few coils off the spring. This depends on how far down you can insert the device (farther is generally better as there will be more water weight on top to open it). Make sure you are ABOVE any kind of standard P trap!2. Once you cut off coils from the spring the spring will now not go the full length of the screw. You need to buy some very small washers to fill this gap.3. Tune the tension of the spring and the amount of washers with the device MOSTLY tightened. As you tighten the device it changes the length and therefore the amount of seal the float will make. If you decide on the amount of washers when it is fully loosened you will be in for a bad time when the float now no longer seals via the spring.I used in total about 5 washers after a lot of experimentation and I cut maybe 4 coils approximately off the spring. I tied a small string to the middle bar of the device in two places (on either side of the screw) so I could lower it evenly. Make sure to carefully tighten each side evenly and if it gets at all misaligned / angled within the pipe start over. If its angled then its not going to form an air tight seal. I also put lasco pure silicone grease over the O-Ring and the float to make sure it sealed better (only use pure silicone grease). And make SURE you lean the crap out of the inner wall of the pipe you are lowering into - I used a wire brush. I was only able to insert it a maximum of about 8 inches down but this setup now works great for me. No more sewer gas smell and hopefully no more backups!

This important piece keeps our basement from flooding. Prior to buying this we had several inches of water up from the drain. Now we are protected after strong rains.

My basement floor drain pipe is 4 1/8" I.D. 4" size was a little loose. I tightened all four screws compressing the rubber and it fit inside the pipe perfectly. Nice and snug. Poured a bucket of water down the drain and it drained right away. No way to test the back water float stop after it's installed but I don't see any reason the float wouldn't seal if I have a back up.

This looked like a used product when it arrived, complete with a broke box. I was OK with that thinking about what I was going to use this for but it didn’t fit my 4” drain opening, the screws were too short and the rubber seal around the outside was too stiff. After this failed, I ordered from Grainger, item had the same specs but the Grainger item fit and functioned perfectly. Had to send the Amazon item back. Note: Grainger item as more expensive, but it worked while this one did not.

It did not fit perfectly in a 4-in cast iron sewer trap. It might fit perfectly in a 4"PVC trap.

Super easy to install...the 4" fit right in my drain and just had to tighten the screws. Seems secure, I can't pull it out. This should help my anxiety when it rains. Not sure how good it will work, but I don't see why it wouldn't.