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Mike P. · Joined: 08 Mar 2006 Posts: 10

Hello

I have one each of these fitted on the supply pipes to my pumped shower mixer valve. I've had reason to fix a leak at one of the supply pipe joints at the mixer valve (access from airing cupboard) and during the repair process, before turning everything back on, I decided to check for any air in the supply pipes by going up into the loft and trying to bleed air from each of these caps.

The first knurled cap (hot supply) undid fairly easily, but the centre of the small neoprene washer in the cap was molten into the bleed hole of the vent! This is surprising since the installation is only about two years old. Fortunately, this stops any water bleeding out while the cap is off and so I prised out the remainder of the washer from the cap.

I've pierced the molten neoprene with a small safety pin, but of course when you take the pin out, the hole more or less closes up again. I plan to use a very mall drill bit in a hand drill to clear this bleed hole.

These washers are pretty thin and I had not got a flat neoprene washer small enough or as thin. I have one or two larger and probably twice as thick, so I carefully cut out a replacement from one of these and pushed it into the top of the cap until it bottomed before relacing the cap.

My concern here is that since the replacement washer is thicker than the original, the cap is being held on by a turn or two less than before. Do you believe this will be a problem?

Of course I could go to a plumbers merchant and buy a new end feed air vent and simply cannibalise the cap (assuming the threads are all standard for 15mm pipe components) - certainly don't want to go to the lengths of replacing the complete soldered air vent - but this seems a waste if my improvisation is considered effective.

thescruff · Moderator Joined: 03 May 2003 Posts: 4400 Location: Bath

Should be ok provided it's not hanging on with a couple of threads

Mike P. · Joined: 08 Mar 2006 Posts: 10

Thanks for the comment thescruff. Well, of course that's the problem. It's hard to tell because I think these caps are slightly wider at the bottom, so the first thread or two don't seem to fully engage. I imagine therefore the cap is now holding with no more than three turns. Borderline isn't it?

I may have to phone round a few plumbers merchants to see if they stock any thin neoprene washers. Don't hold out much hope though.
The melting of the washer into the vent hole is odd though, isn't it? Surely these washers are supposed to withstand hot water temperatures - that's what they're designed for, after all.

thescruff · Moderator Joined: 03 May 2003 Posts: 4400 Location: Bath

I expect the washer has been tightened too tight, unlikely to have melted.

Have you look at PTFE tape for gas to make a washer.

Another trick if you have an open tube is to squirt an thin layer of silicon in the cap and allow to dry, it's easy to makes washer that way but expensive to buy an tube specially

Mike P. · Joined: 08 Mar 2006 Posts: 10

Hello again thescruff.

Well, I tackled the cold water cap today. As the hot water vent hole was still blocked, I was able to have that cap ready to put on the cold vent as soon as the water appeared. Good job I did, as I had forgotten to turn off the pump! A powerful stream of water shot up into the air before I could put my thumb over it, get the cap on and turn off the pump. No harm done; most of the water that did escape landed on the loft insulation and will dry.

I used a pair of pliers to nip up the cap gently.

The cold water washer was deformed in the middle into the vent hole (but had not blocked it) and stayed there when I took the cap off. It was when I lifted the washer clear that the water exploded.

I made a similar cut-down washer from my 3mm thick neoprene washers and put this in the ex cold water cap now to be swapped to the hot water valve. Before doing this I cleared the hot water vent hole with a very small bit in a hand held drill, when water came out more sedately before I screwed the cap on, again nipping it with pliers.

It's funny you should mention silicone sealer, as my final step was to put this completely round the outside of the bottom of both caps to act as a locking ring, preventing the caps from working loose. This is an added precaution as these vents are out of sight in the loft and could leak for ages without being spotted. Should the caps need to be undone, the sealer can be removed externally fairly easily.

At one stage I did sit the cap down on top of the valve to see how far above the threaded section the top of the cap came, thereby seeing how much space had been allowed in the top of the cap for the washer when the cap is in situ. I don't think my 11/2 mm thicker washers are going to be a problem.

Anyway, fascinating stuff and thanks for your interest.