So, how is this supposed to work ...?

[Arfa Daily]

My Plumbworld pressure reduction valve

yesterday, and it looks a perfectly well-made piece of kit, so I look forward to getting it installed to see how well it works. However, see that pressure gauge on the side ? As someone else commented last week when I was asking on here about these devices, it comes with the gauge in a separate box, and a plastic blanking plug in the hole in the valve body, where it would fit. The instructions merely say screw it in after removing the plug, and leave it in place or not, at your discretion, after initially setting the output pressure. Fair enough. But here's the trick. As the other poster also commented, the threads on the gauge are not tapered - and are actually quite a 'slack' fit in the valve body - and they are not long enough to allow them to 'bottom out'. Now you would think that there would be at least a fibre washer supplied to give the gauge something of a seal at the bottom, and something to tighten against, but no, there is nothing. So, how does this work ? How do they expect people to get a seal into the gauge ?

I dropped a couple of M5 red fibre washers down the hole, until the gauge hand-tightened at something less than 180 deg from where I wanted it, and then pinched it up 'square' with a spanner. I also wrapped the threads with PTFE tape, to make them a 'smooth' fit in the valve body, as I intend leaving the gauge in place permanently.

Anyone see any problems with the way I've done it ?

Arfa

[Dave Liquorice]

PTFE tape I should imagine. Anything that "bottoms out" will probably bottom out with the guage facing the wrong way...

Presumably so they can be aligned in the desired direction.

Where does this crap come from on a potable water supply? How does it get in there from the supply if there is no movement? Removing it, one assumes that the supplied plastic plug is good enough to seal and not fail at some point in the future...

[Nightjar]

That is much the same way (I used PTFE paste rather than tape) I attached pressure gauges to an air supply working at 7 bar and that didn't leak.

Colin Bignell

[Tim Watts]

That was me.

If your fibre washers seal now, they should get better rather than worse with time as they expand when wet.

I think you'll be fine.

I just stuffed my threads with PTFE (IIRC) - might have been Loctite plumbing thread sealant.

I do wonder who designs this stuff - the principles of using either tapered threads or having flat mating bottoms for a washer are well established - why make the device a bodge fit?

[docholliday]

Just about all the pressure gauges I've had to deal with came with parallel BSP threads (if it's shown as G1/4, for example, that's a quarter inch parallel BSP). You can also get them with taper threads but for some reason they are NPT not BSP, and there are some subtle differences which can be a pain in the a**e. The ones with parallel threads should come either with a flat bottom for use with a sealing washer or with a projection that you're supposed to fit an O-ring to. I'd have thought that if they're supplied in a kit like this the appropriate seal shoud be included, but experience shows that manufacturers often don't think the same way ;( While fibre washers aren't exactly what the maker would have intended

- they're probably thinking of something like this

can't see it as a problem Mike

[Steve Walker]

they were generally known as Dowty seals.

On older specs (such as old ICI ones) they used to spec parallel BSP threads and greased leather washers!

SteveW

[Arfa Daily]

Yes, that was my feeling too, but there is no seal supplied. At the end of the day, this gauge is on the outgoing side of the PRV, where the 'new' pressure will be restricted to 3 bar, so I can't see that a couple of fibre washers between two flat surfaces, is going to leak any. I was just interested to see the opinions of the good folk on here, and to make sure that I wasn't missing anything. I've been doing DIY plumbing for more than

40 years, so pretty experienced, but that still doesn't make me any kind of expert ...

Arfa

[Arfa Daily]

A friend offered me one of those. Apparently, they are used in hydraulic installations and proof to a coupla thousand PSI ! I'd already fitted the fibre washers, and that seemed like a bit of an overkill, but at least I know where I can lay hands on one quickly, if I have to.

Arfa