I got a backwater valve installed in my basement. The water table was high, so I could not use a backwater valve with a see-through cover; I had to use a valve that is typically used for outside installations. I can access the valve for maintenance through a 6" wide PVC pipe (see picture).

With the see-through backwater valve, one can easily see if there is a backflow situation. There are also some alarms that can be used to warn of backflow situation. However, with the current setup I can't see if there is a backflow situation without opening the 6" cap. This could be a bad idea if sewage starts spilling out of the open pipe. So I am thinking that it would be great if the cap was transparent. I couldn't find such a cap googling around. Is there such a thing as a transparent 6" screw on cap?

What tool does one use to open & close these caps anyway? It is a 2" counter sunk square.

Also, since it seems that off the shelf alarms don't exist for these 6" cap, I was thinking of making my own with an off-the-shelf water alarm combined with the cap. I would have to drill some hole(s) through the cap (transparent or not) and feed the wire through. The plate would go inside the pipe and the alarm outside. How would I seal the hole around the wire? It would have to be airtight, and strong enough to resist a backflow pushing up against it.

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1 Answer 1


Clear PVC does exist and you might be able to locate some from Commercial Industial Supply (for example).

With regard to gluing wire (insulation) to PVC, a copious amount of epoxy or silicone should work. Luckily, the pressure should not be extreme. The most important instruction is to drill the hole just large enough to slide the wire though without pinching or damaging the insulation. For the best result, the connection (wire in the hole) should be practically air tight before using glue. But glue won't last forever.

What tool does one use to open & close these caps anyway?

Looks like you need a cleanout plug wrench or a Square for Counter-Sunk Clean-Out Plugs.

Edit- based on comment that a wrench could not be obtained- Well, 2 inches is kind of large; perhaps a drum plug wrench is waht you need.

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You just need to get anything (a hard piece of wood or metal) that is 2" x 2". But I think that a piece of plywood might be strong enough (birch would be preferable to pine). Cut a piece 2" x 2" (of course) and cut a nice long, wide handle. Pre-drill 4 holes in the corners of the 2" square before using screws (to avoid splitting the wood). Apply plenty of glue and screw the small square piece to the face of the handle. It might not work forever, but it will probably work a few times at least.

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  • Awesome answer, thank you very much. Funny that a cleanout plug wrench (which is the complete tool from what I gather) is cheaper than a square for counter-sunk clean-out plug (which is just an end to use with an existing wrench).
    – Jimmy
    May 11, 2016 at 15:36
  • @Jimmy I didn't shop for the lowest price tool, I just linked the first thing that I saw. With a bit of hunting I think you could do better. May 11, 2016 at 15:48
  • The counter sunk square is 2" by 2"... still have not been able to find a wrench or square that large :(
    – Jimmy
    May 17, 2016 at 13:32
  • @Jimmy editing my answer May 17, 2016 at 14:20

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