I need to use the clean-out valve to clear what's likely a blockage. I think I found the right one (more or less directly below the second floor bathroom that's misbehaving).

It looks like it was painted over. I chiseled and scraped away the paint to see where the seam is so I can try to open it but it looks like it's somewhat embedded in stucco.

What should I do? Am I right that the seam is a few inches in from the top?

Update: The lower seam (below the ribs) is where the cap receiver was glued on. Sadly the cap was glued in and has since become quite brittle. When I tried to remove it after scraping all surfaces clean it just kept cracking; I've carefully removed most of it but parts of it are stuck in the threads (glue!) - I was hoping that once I had a split down the length of the cap's edge I'd be able to peel it out but not even close.

I think my next step is to cut the receiving end down the side through and chisel it off which will be easier than clearing out the threads. With that off I can buy a new cap/receiver set and glue it on in place.

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  • Do a google image search for "clean out valve," it will explain better than words. It looks to me like the paint is preventing you from unscrewing the cap, and the cap itself is broken (the holes in the boxy part).
    – negacao
    Commented Feb 11 at 22:42
  • Yep I did, there are a few different styles of these. Given that there are gripping 'ribs' below the top flat surface I expect that the seam is below the ribs. If that's the case I fear I have to chip it out. Also if that top part is functional (ie effluent can reach it) then I have to replace the cap... but IDK so I'm asking.
    – Ram
    Commented Feb 11 at 22:44
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    Seam not below ribs. Don't chisel out the ribs. The mortar is holding the fixed end in place. The cap has male thereads and fits inside the female end fitting which the moratr is helping to support. It is not a "valve" it is a cleanout opening or just a cleanout. Commented Feb 11 at 23:25
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    Even better, go to your local big-box store and pick up a threaded end and clean-out plug so you can see how they go together. Some stores actually sell them as a matched set, some sell the 2 parts individually. Once you see it live, in person, and play with it a bit (insert/remove the plug), you'll have a much better understanding of what you've got at home and will know how to remove it without damaging the wall or pipe.
    – FreeMan
    Commented Feb 12 at 14:30
  • Does that 3” or so pipe pass through any accessible space? It would be way easier to cut it further down and attach a union to an extension that had a cleanout on the end. Commented Feb 12 at 21:07

2 Answers 2


Be careful working with tools in the opening of this drain. It is very easy to drop a tool down the drain. One wrong move or loss of concentration and it's gone! This could lead to an obstruction in a main drain. When working on my cleanout I have sometimes tied a cord onto tools and secured it with duct tape.

Unless some uninformed person used cement on the threads, you should be able to destructively remove the cap. Cut away the cap from the inside or fracture it with channel locks or straight pliers down to a small rim. Try to not drop large pieces of plastic into the drain.

You might be able to use the channel locks or straight pliers to fracture the cap all the way to the rim. Once you have removed part of the cap all the way to the rim, the rest should come out more easily.

Alternatively cut the remaining rim radially with a hack saw type saw, then either pry with a screwdriver at the threads to break the rim inward or pull inward by gripping with pliers.

When installing PVC or ABS threaded caps, I sometime use silicone grease on the threads. Petroleum grease on plastic is not a good idea because it damages some plastics.

If you end up damaging the female threads, you could use a cap which seals by friction with a rubber seal. Some replacement cleanout caps expand with a lever or twist. These are OK for sealing the cleanout because liquid does not stand there.

What you do not want to do is fracture the female end fitting. If that happens, you will have a much more expensive and time consuming repair.

  • The saw is a great idea. Least likely to break the fitting and the cap is already broken. Don't even have to slice the paint (and maybe cut yourself), it will break apart when the sawn cap becomes flimsy enough.
    – jay613
    Commented Feb 12 at 23:10
  • Seems like great advice. I tried ripping out the cap using a plier to start it and then using a small screwdriver to try to crack down the length of the cap's threads so I could peel the rest out - sadly it is stuck on there good. I've managed to remove perhaps 60% of the cap threads but they are cleary glued or bonded somehow. It seems I will have to remove the female end of the joint and glue a new female end on.
    – Ram
    Commented Feb 21 at 17:40
  • Don't think you have to remove the female fitting. Worry away or grind away the remians of the cap and male threads, then get a cleanout plug that slips in and expands to seal. This will be either a 3" or a 4", I think. What is the diameter of the threaded opening? This is not a joint that actually requires a threaded plug. homedepot.com/p/… Commented Feb 21 at 19:48

In all probability, the threads are in the ribbed section. (Not below the ribbed section where you’re chiseling.)

Get a long wrench on the square part and turn counter clockwise.

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    OP should go get a new cleanout cap and see that they have male threads and fit inside the part he is apparently chiseling! He should scrape the paint away from the joint of the cap and see if he can turn the cap. This is probably a "3 inch" cap even if the diameter is a little over 3", but might be "4 inch". OP might have to counterhold the ribbed part with large channellocks or a strap wrench, but it might come loose without that especially if he removes the white paint from the edge. Commented Feb 11 at 23:09
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    I'm chiseling the adjacent stucco, to see if what looks like a seam goes all the way around. I'm not touching the plumbing afaict.
    – Ram
    Commented Feb 11 at 23:23
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    Seriously, you’re doing it wrong. The ribbed part is glued onto the pipe. The plug with the square lug is threaded into the ribbed part. Commented Feb 11 at 23:25
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    Hitting it with a hammer could break it. If this is pllasstic it could be fragile. Better to lightly cut the paint at the seam with a utility knife or scrape it away with a sharp chisel. Commented Feb 11 at 23:35
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    This question contains pictures of a similar but broken plastic cap screwed into a vertical pipe. The cap and pipe in the pictures are not obscured with paint. Commented Feb 12 at 0:06

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