Help: Leaking drain-off valve

I've fitted a new immersion cylinder but am having a problem with the drain-off valve. When I bought the valve I thought it should have a fibre washer, but a friendly plumber told me that it doesn't and I should instead use 13 turns of PTFE tape. The problem is that even though I've tried this a few times I can't get the damn thing to point downwards - and it leaks! (the irony - having to use the drain-off valve for the first time because IT leaks... grrrrr.) To me it doesn't seem right: the face of the valve seems smaller than the face of the outlet on the cylinder as if something else should be there. Searching the archives has left me thinking that this is a

1/2" BSP parallel thread and that what the plumber told me is probably correct, but it still seems odd (to my naïve plumbing skills) that the immersion element came with a nice washer but the valve didn't. I'm going to try again this morning with even more tape, but thanks if anyone can put me out of my misery and tell me if I'm doing anything wrong. I've put a picture up here:
formatting link
Reply to
DJB
Loading thread data ...

You need LOTS of tape, and you can't unscrew it at all to get the position right - you have to stop exactly where you want it. There are alternatives to PTFE that are easier for where the final position is important - my current favourite is screwfix code 42142. More expensive, but you don't use much, it works every time, and you can back the fitting off if you need to without breaking the seal.

A
Reply to
auctions

He's right, these should just screw in and have PTFE tape - no fibre washer.

One thing that can happen on some fittings - some cylinders and radiators are bad for this - is that the thread tolerance is a bit poor to the extent that the fitting is rather loose.

This suggests use of a lot of turns of PTFE tape (like his suggested

13), but sometimes the tape is then cut by the thread or bunches at one end and the fitting leaks.

I've found two solutions that generally work well.

- Get some PTFE tape for gas. This comes on a yellow reel and is thicker than the mimsy stuff for water. Try about 4-5 turns or so on the fitting and screw in by hand. It should be possible to turn the fitting in your fingers with a certain amount of effort but it should not require a wrench until final tightening and should not be so loose that it turns easily. If either then remove and apply more or less tape as appropriate.

- Get some Boss Green and some hemp. Apply a small amount of the sealing compound then wrap some hemp onto the threads (right way round as for tape) and finally another smear of compound.

Both should work well and you should not have a leak.

Reply to
Andy Hall

Thanks both of you for the fabulously quick replies, I'm off to the plumber's merchants now :-)

Reply to
DJB

The plumber's merchants didn't stock any of the Screwfix/Loctite 55 pipe seal cord, nor did they have any hemp saying that there was no demand for it these days, but what they did suggest was a combination of gas PTFE tape in a Boss Green sandwich which seems to have worked, no leaks :-) The valve still points upwards but I think I'll live with that, hopefully I won't have to use it again for a long long time...

Reply to
DJB

Does Boss Green harden with time? ideally one woul dlike a compound that you can tighten to the required position and then leave to harden. I ihave the same problem as the OP but with an outdoor tap screwed onto a projecting female threaded pipe. it always points at abotu 45 degrees insead of vertical seemingly regardless of how much I try to pack it..

R
Reply to
RobertL

Be nice on parallel BSP if there was a thin nut as well, to lock the fitment into position.

Reply to
Tony Williams

Or loctite 55 pipe sealing cord - looks like dental floss. Works really well. Lets you slacken a fitting aftrer tightening and still get a seal.

Reply to
Ed Sirett

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.