How to cap off 15mm water pipe

sjones12121994

kimwp said:

I attempted a small plumbing job and now lots of things are leaking. 

Main issue is how to cap off this pipe (see photo) I thought I would just be able to turn the isolation valve to block the flow, but it's leaking. I think I have two DIY options - cap off the isolation valve or cap off the pipe (which I've successfully reattached to the valve). A cap on the isolation valve would be neatest, but I'm not sure what I'm looking for - I can only find compression end caps - if it's the same thing another compression fittings ie with an olive, I don't think this would be the right thing as there's no pipe for the olive to be compressed onto? Can anyone advise on what I should be looking for? (Or doing - with the pipe or generally in life, I'm open to suggestions at this point)

(I know I've fitted the flexible pipe with the isolation valve facing the wall, I didn't spot that it had one

You can cap off the isolation valve with a blanking cap. Look for a valve blanking cap or stop end that matches the size of your valve. It usually has a flat end to seal the valve. If you can't find one, capping the pipe with a compression end cap is a good alternative. Make sure to shut off the water supply before attempting any fixes, and consider getting a professional plumber if you're unsure.

kimwp

Finally got round to getting compound (work has been busy), but it looks a bit more solid than I was expecting... Is this the right stuff?

ThisIsWeird

kimwp said:

Finally got round to getting compound (work has been busy), but it looks a bit more solid than I was expecting... Is this the right stuff?

I haven't used that actual stuff, and it's hard to judge how solid it is from the photo. Can you give it a mix? If you wipe your finger over it, does some come off that you can smear on to the olive and threads?

Slightly different product, but similar thickness?:

https://www.youtube.com/watch?v=essm_Y1dBxk&t=129s

FreeBear

kimwp said:

Finally got round to getting compound (work has been busy), but it looks a bit more solid than I was expecting... Is this the right stuff?

Ithas the consistency of putty or a stiff mix of filler.

As for being the "right stuff", I still maintain that you shouldn't need any sealant on a compression fitting.

kimwp

Ace, thanks both! I applied it to the insert as in the video, but I used the clip bit of a biro cap as a tiny shovel rather than my finger.

So I have a compression joint with PTFE on the outside of the olive, one with compound on the outside of the olive and one with the existing olive and tiny bit of compound - all watertight. The joint with the existing olive was watertight after I took it off and put it back initially, but when I accidentally loosened it trying the take the stop cap off, I added some compound for funsies. 

Thank you mse-ers for your help with this- I'm very grateful and feeling a lot more confident 🙂

FreeBear

PTFE tape is used on tapered threads (for example, the tails sticking out of a radiator). It serves no purpose on a compression fitting.

kimwp

FreeBear said:

PTFE tape is used on tapered threads (for example, the tails sticking out of a radiator). It serves no purpose on a compression fitting.

I put it round the olive, on the sealing surface, as I didn't have compound at the time. 

https://youtu.be/njoB-N8hX5w?si=M2LJb3Sr3623wz7f

ThisIsWeird

That all sounds fine, Kim. (I like that YouTube plumber).

Yes, a wrap or two of PTFE over the olive is fine as an alternative. 

Compound is better, tho'. Just a smear over the olive as in that vid, but I'd also recommend a smear over the exposed male thread of the fitting, as it acts as a lube. You will then not only avoid the hellish screech of the olive and the even worse creak of the nut, but being lubricated means you can much better sense how tight the fitting is becoming; all the resistance you will feel with your wrench is proper 'olive-compressing' resistance, and not useless friction.

If you are new to compression fittings, it can be hard to know how tight to make a fitting. One way to judge this is to do up the nut and keep checking if you can still rotate the pipe in the fitting - it'll become very obvious when the olive has compressed enough to grab the pipe, and make it impossible to turn. At this point, it usually only requires around a half-turn extra to secure the seal, but also act on how more stiff it is becoming to turn. Again, with a lube'd thread and olive, virtually all the resistance you feel is true 'sealing' effort.

 

kimwp

ThisIsWeird said:

That all sounds fine, Kim. (I like that YouTube plumber).

Yes, a wrap or two of PTFE over the olive is fine as an alternative. 

Compound is better, tho'. Just a smear over the olive as in that vid, but I'd also recommend a smear over the exposed male thread of the fitting, as it acts as a lube. You will then not only avoid the hellish screech of the olive and the even worse creak of the nut, but being lubricated means you can much better sense how tight the fitting is becoming; all the resistance you will feel with your wrench is proper 'olive-compressing' resistance, and not useless friction.

If you are new to compression fittings, it can be hard to know how tight to make a fitting. One way to judge this is to do up the nut and keep checking if you can still rotate the pipe in the fitting - it'll become very obvious when the olive has compressed enough to grab the pipe, and make it impossible to turn. At this point, it usually only requires around a half-turn extra to secure the seal, but also act on how more stiff it is becoming to turn. Again, with a lube'd thread and olive, virtually all the resistance you feel is true 'sealing' effort.

 

Amazing, thank you for these tips! When doing the compression joints today, I did largely hand tighten then tighten a bit more with the wrench, with no squeaking, the lube sounds like a good trick though.