PRV valve loosing pressure. Just replace..again?

[busbyuk]

Hi,

We have a Glowworm 38CXI combi boiler. Back in September last year I noticed that it was losing pressure and I was having to re-presurise it almost daily.

From looking outside I could see the pipe coming from the PRV valve was leaking quite a bit. As such I got a plumber in to check over the boiler and replace the PRV valve. This has been fine since then but suddenly the issue is back again.

I'm having to repressurise the boiler each morning due to it dropping down to 0.3 bar. I'm pretty sure the heating is causing it to lose pressure faster. To test this yesterday I pressurised it up to 1.2 bar and left the heating off all day. It maintained the pressure at around 1.2 bar without issues. Overnight however the heating kicked in and I woke up to it again at 0.2/0.3 bar.

It's not a problem getting the PRV replaced again but what I'm not sure is..

1) Why would it need replacing so soon? I thought maybe grit or something caught but I've tried knocking it with no luck.
2) Why would a faulty PRV drop the pressure all the way down to 0.3 bar? IF it was releiving pressure at a lower bar then why would it continue all the way down to 0.3 bar?
3) Why only when the heating is on? I figured when the heating is on then lots of water is heated causing higher pressure and the PRV to have to releive some of that but I'm not sure if this is correct?

I've checked around the house for leaks and I can't see any damp patches on celings or radiators. The outside pipe from the PRV valve 'is' leaking so I think this probably hopefully means it's unlikely to be a leak in the house?

I will go around bleeding the radiators but I'm not sure if this would have any bearing on this?

Thanks in advance.

 

[SimonG]

Hint: it's not the prv. The issue will need a gas safe engineer to rectify.

I would suggest somebody more intelligent than whoever blindly and unnecessarily replaced potentially a perfectly good prv.

 

[king of pipes]

How many rads do you have ? First thing to test is the internal expansion vessel not something you should be doing i am afraid and you may possibly neec a extra one externally. Kop

 

[busbyuk]

How many rads do you have ? First thing to test is the internal expansion vessel not something you should be doing i am afraid and you may possibly neec a extra one externally. Kop

Thanks.

9 radiators in the house in total. I'm going to go around them all this evening and double check for any leaks and at the same time bleed them all. No idea if this will make any difference.

Back in September when I first had the PRV replaced by a plumber, he tested the current expansion vessel which looked fine. It doesn't mean it hasn't since failed of course.

From my reading if it was the expansion vessel which has failed should I be seeing it creep up to around 3.0 bar before the PRV kicked in? The pressure never seems to climb above 1.6bar before losing pressure and only when the heating is on. This is at the moment pretty much just overnight as there is less need for the heating to come on in the day.

 

[John.g]

The only way that a healthy PRV will leak at ~ 1.5 bar is if its a 1.5 bar PRV, highly unlikely that the incorrect ones were fitted in either case. Can you just re pressurise your system to 1.2 bar when cold then fire up the boiler with all rads (zone valves, TRVs etc opened) and sit in front of the boiler and watch the pressure rise for ~ 45 mins, also look frequently at the PRV for any discharge and post back.

 

[Stigster]

Thanks.

9 radiators in the house in total. I'm going to go around them all this evening and double check for any leaks and at the same time bleed them all. No idea if this will make any difference.

Back in September when I first had the PRV replaced by a plumber, he tested the current expansion vessel which looked fine. It doesn't mean it hasn't since failed of course.

From my reading if it was the expansion vessel which has failed should I be seeing it creep up to around 3.0 bar before the PRV kicked in? The pressure never seems to climb above 1.6bar before losing pressure and only when the heating is on. This is at the moment pretty much just overnight as there is less need for the heating to come on in the day.

Any air trapped in radiators would actually be helping the overpressure situation by acting as an expansion vessel. The PRV could be a 1.5 bar type but that would be highly unusual. It's more likely that the gauge is not giving a true reading if it really is discharging at 1.6bar

This is an expansion issue rather than a PRV issue I believe.

 

[busbyuk]

Thanks all. I'll give another quick search for a leak this evening (to be safe) and then call a different plumber in to get the expansion vessel checked

Thanks

 

[RoryD]

As Simon said, it isn't your PRV. Really, call an Engineer mate.