Capping off waste pipe connectors to soil pipe

[LostDutch]

Good afternoon everyone,

I'm finishing up some DIY work in our bathroom and two waste pipe connectors to the cast iron soil pipe are not going to be used anymore so I need to close them off. As flush with the pipe as possible, since I'll need to box around it.

I'm unfamiliar with the correct plumbing terms, so just to make sure that it's clear what I'm talking about: I'm seeing a rectangular lid that's bolted to the soil pipe. There are two threaded waste pipe fittings on this lid with coupling nuts. One piece of waste pipe at the bottom is still connected, the one at the top I was able to take off.

Unfortunately, I'm not able to find any parts that fit on these threads. And I haven't even tried taking off the rectangular door part off since I wouldn't be able to find a replacement for that anyway (although I could make one I guess).

I bought a McAlpine 1 1/4" compression stop end, thinking that since 1 1/4 inch is 31.75mm, surely the cap won't be too large like the other caps that I still had. But it's too large! How is it possible that a cap for a 31.75mm pipe would be too large for a 34.7mm opening!

Any advice on closing/capping/sealing off these fittings? It's fine if it's permanent.

 

[LostDutch]

Small update: I looked up a conversion table and a some explanation with silly historical excuses why this is so complicated and it occurred to be that I still had a bathroom sink waste, which is supposed to be 1-1/4 Inch BSP. And the coupling nut at the top is a match! So I assume something like the McAlpine 1.1/4 inch BSP Threaded Blank Cap S23 would work well for that.

I am assuming that the fitting at the bottom is 1-1/2 Inch BSP and not 3/8 Inch.

Now I still need a way to get the bottom coupling nut off! Please do let me know if it makes sense to remove the whole lid/plate/door, because that would save some space.

 

[Hugh Jaleak]

Removing the entire plate would be preferable, but my concern would be, should you snap of (or more) of the bolts, you are left with a bigger job of trying to remove broken bolt and/or retap the thread.

Do you still have the Nuts that secured the waste pipe to the fittings? Thinking use those, to retain a suitable cap cut from a piece of plastic perhaps?

 

[LostDutch]

Removing the entire plate would be preferable, but my concern would be, should you snap of (or more) of the bolts, you are left with a bigger job of trying to remove broken bolt and/or retap the thread.

I think it's worth mentioning that this is on the first and top floor of the house, so leaks or pressure aren't I concern I'd think. Unless the soil pipe gets blocked further down, but then leaks in that particular spot are the least of my concerns.

Any idea where or how I might be able to get a plate like this? If the bolts are made of the same quality steel that was used in the soil pipe I had to saw through elsewhere in the house, snapping isn't something I'm concerned about. But even if one of them snaps off I could always grind it off, I reckon that fixing a new plate to it using the other three bolt and a nice bead of hybrid polymer will outlive the house.

Any idea what such a plate might be called or where to get it?

Do you still have the Nuts that secured the waste pipe to the fittings? Thinking use those, to retain a suitable cap cut from a piece of plastic perhaps?

Yes I do. I considered this and it's my backup solution, but was hoping I'd be able to solve it in a way that you're "supposed to do it". And additionally, I only removed the boxing around the pipe where necessary. If I were to patch it up again, such a solution would just about not fit, which would be a shame.

 

[Hugh Jaleak]

If you can get the plate off, I'd be more inclined to look at making something out of a suitable piece of plastic, e.g. Perspex, which can be sealed with mastic. Pipework is likely cast iron, getting a match for the fittings used is probably going to be like looking for a needle in a haystack, if they're even made any more, so I'm afraid a 'work around' is probably going to be your only option here, without resorting to cutting sections out the stack.

 

[JimCrow]

Using the existing nuts,

You may have to trim them down a little so the brass nut fits over them.

 

[LostDutch]

Using the existing nuts,

View attachment 307508View attachment 307509View attachment 307511
You may have to trim them down a little so the brass nut fits over them.

This did the trick!

I didn't trim the washers down, but it would have made it a lot easier. I first put the washers in the existing nuts, applied some silicone spray to the socket plugs and wrestled them into the nuts. Then I adjusted the rubber washers a bit with a flat screwdriver where I had pushed them out. With a bit of pressure I could get the nuts back on the soil pipe fitting.

I bought a strap wrench this week to be able to undo the bottom nut. That one came in handy again today to fasten the nuts. Amazing tool for DIY.

Thanks @JimCrow !

@Hugh Jaleak I was able to turn two of the bolts easily, so I expect I will able to get the plate off if need be. Will implement your suggestion if it turns out I need the space when boxing in the pipes. Thanks for your help!