Boiler rapidly losing pressure

Belenus

Is it worth opening up the pressure release valve for a few seconds, letting some water out and then closing it again to see if it reseats properly and stops leaking?

Or is that more likely to make the leak worse?

Bendy_House

Belenus said:

Is it worth opening up the pressure release valve for a few seconds, letting some water out and then closing it again to see if it reseats properly and stops leaking?

Or is that more likely to make the leak worse?

Unlikely to make it worse, although it is a gamble. Chances are if you keep trying it, you will find a better seating. But that's only 'chances'...

Looks like a rotating knob? In which case I think you'll find it turns continuously, with the valve being 'open' at the half-way point. It will be acting against the spring which is trying to keep the valve closed, so the first half-turn will be pulling up this spring, then there will be a fully-open point where the knob can likely be persuaded to stay - teetering on the top - and then it'll pull shut as you continue the movement around to the starting point - does that make sense?

So, I'd suggest you turn it that half turn to get it fully open (it could be a quarter-turn, I guess, but you'll feel it), and then quickly snap it round the rest of the way, so that the valve springs shut with a bit of firmness.

Belenus

Thanks Bendy_House for that and all your other comprehensive replies.

It is kind of you to spend so much time helping me and others on here.  

Bendy_House

Thanks, and you are welcome - and it works both ways

Belenus

Belenus said:

Is it worth opening up the pressure release valve for a few seconds, letting some water out and then closing it again to see if it reseats properly and stops leaking?

Or is that more likely to make the leak worse?

Another Update.

On Monday I opened the PRV a few times.

The leak has slowed down considerably such that drops are no longer visibly falling into the tundish. However the opening of the pipe into the tundish remains damp so I think water is still leaking very slowly.

The pressure is still dropping but very much more slowly than before. It now takes about 6 days to drop to 1 bar whereas before it would drop to that within less than 24 hours.

I will probably just live with it for now or I may buy a new PRV and fit it myself when the weather is warmer and we don't need the heating on.

Bendy_House

I recall it was a relatively straight-forward plumbing job. The lower 'outlet' pipe from the valve is removed fully, and this isn't an issue in any way as it isn't under pressure even in actual use.

Then - looking at your photographs - it looks as tho' the whole valve is unscrewed? That means it needs refitting not until it's fully tight, but until it's tight enough whilst still being upright! I hate these sorts of things - you always wonder if you could give it one more turn or not...

If that's the case, what i would do (what I probably did do) is to do it up 'dry' (no sealant or PTFE tape) and count the number of turns it takes to be fully done up. Back it off the amount needed to get it sitting vertically, and count that number of turns. And/or, do it up fully, back it off, and then photograph a close-up of the number of threads still visible - that's your guide.

Then apply Hawk White or similar, and redo it to the correct point.

Phew - pleased you managed to get it seated better! That could have gone the other way

Oh, and when you get your new valve, resist the urge to twiddle with the knob...

If you over-fill the system at any time, use a rad bleed screw to release any excess pressure.

Belenus

Yes, it should be straightforward to replace the PRV.

It is a push fit into the four way union on the return pipe and is held in place by a securing clip.

A standard compression fitting attaches the pipe below to take any discharge into the tundish.

This picture from google shows the valve. On the left you can see the push fit part with a black O ring and a groove where the securing clip fits.

Bendy_House

Ah! Yes! That's it Easier still - a true DIY jobbie.

And a tube of silicone grease should be in every household

Probably worth checking the pressure of the internal EV too, while the system is depressurised. If it needs some pumping, be sure to have an outlet for the system water as you do so - like a rad bleed screw open.