Woke to a wet patch under a TRV - potential cause and possible fix?

BooJewels

Good morning.  I woke this morning to a wet patch under the bathroom radiator and wondered the potential cause and possible fix, before I call anyone out - if it's hopefully a one off or I can sort it myself.

I had a new boiler fitted at the end of November and the system was supposedly flushed and treated at that time.  It has taken me a little while to get all the radiators balanced again and rooms at the temperature I want.  But it seems to have been working fine for the last month or so.

Last night as I was preparing for bed, I heard a few familiar gurgles and a couple of quite loud pops from the system that suggested a bit of air (the sounds always seem to come from the kitchen radiator) and I intended bleeding it, but forgot.  I tend to bleed air from this bathroom radiator as I think it's the first in-line after the boiler and it seems to be where air accumulates and bleeding here usually fixes it.  I had noticed a couple of times yesterday that the bathroom felt cold and it didn't form much more of a thought from there.

The first thing I did when I spotted the wet carpet, was to feel all around the TRV and pipes and bleed nut to see if I could feel where it was coming from, but because it was all warm now, it was dry and has remained so - I've checked it several times.  I've sponged the damp up as much as I can and it doesn't appear to have been added to. 

The radiator was tangibly cooler than I'd expect and more so at the top, so I bled the radiator and a lot of air came out, perhaps 30 or more seconds of hissing before a gurgle of water - and the radiator then got hot all over.  I did it again a bit later and got a smidge more.  No further leak, no more noises.

Could a bit of trapped air have been enough to cause a leak of this nature?  Anything else that I can check?  I'm usually prepared to have a go at most things myself and am well able to use power tools etc. but plumbing is totally out of my comfort zone and my knowledge is very limited, so please spell it out idiot-style.

SaverRate

If everything on the pipework/fittings/radiator is dry and you cant see any drips, could it be pipework below the floor causing the leak? This would obviously involve stripping the carpet and floorboards (if applicable). As the pipework comes up through the floor I assume there is no pipework running up the wall?

FreeBear

Do you have a cat or small dog ?

There was a thread a while back with someone else having a wet carpet underneath their radiator. Turns out is was the cat having a pee in the middle of the night.

BooJewels

HarryDavies01 said:

If everything on the pipework/fittings/radiator is dry and you cant see any drips, could it be pipework below the floor causing the leak? This would obviously involve stripping the carpet and floorboards (if applicable). As the pipework comes up through the floor I assume there is no pipework running up the wall?

I've pulled the carpet back as far as I can easily without removing fixing strips etc. and there's certainly a wet patch on the floorboards to match the carpet stained area.  But surely a leak can't be too far below where it's visible, as water generally flows downwards?  ETA:  No, there's no pipework going above the rad, it comes up (and back down) from below.

It has started gurgling with air again in the kitchen radiator and more air has come out.  I think I need to increase the boiler pressure, as the indicator shows it has dropped to just above the 'too low' line on the graphic, so I need to dig the manual out to figure out how to do it on the new boiler.   This is the first time I've bled it from new.

@FreeBear - I wish it were that simple - there's only me here, so I can't blame this one on anything furry.  

FreeBear

BooJewels said: - there's only me here, so I can't blame this one on anything furry.  

In that case, it would be worth getting a spanner on the nuts on either side of the TRV and nipping them up slightly. Less than a 16th of a turn. It is possible that the TRV is leaking from the pin under the head - Unscrew the knurled ring and see if there is any water pooling under the head.

A bit of toilet paper wrapped around the pipe might reveal if there is any water leaking out from the fittings above - Check once the boiler has shut down and the radiator(s) have cooled a little.

TELLIT01

Try wrapping paper towel around the pipe below the valve, but not in contact with the carpet.  That will at least enable you to rule out a leak from the valve or radiator. 

Bendy_House

Hi Boo.

It's common - as I've just found out - for such leaks to occur during the night after the system has cooled down and the fittings have slightly contracted. That, coupled with a hot rad & pipes being able to evaporate much of a slow leak.

I think it's best to try and suss out where exactly the leak is coming from, before starting to tighten up all yer nuts. But, if you just want to 'tweak' them all, go ahead - but give each one literally only a 1/16th-ish turn.

Best to remove the TRV head - simply open it to max setting, and then unscrew the chrome collar underneath - so that the potential source there is also exposed. Then lay newspaper on the floor to catch any drips, coupled with some paper towel around the pipe stem above floor level. Then wait...

Repressurise the system to, ooh, 1.2bar, and either get up early in t'morn before the heating comes on, or else simply turn the heating off for one night so you can check the fittings whilst they are still stone cold. Examine every joint closely, wipe your finger along them, dab then with a tissue - whatever it takes to ID where the leak is coming from.

Then tweak it.

A bit concerned about that quant of air - it just shouldn't be doing that. What's more, most modern boilers have built-in auto air vents to expel any such air. Summat is not right.

Make and model of boiler, please? And how many storeys are in your house? Is there a dated 'inhibitor added' label near or on your boiler? Magnetic filter installed? (If so, when was it last checked?)

BooJewels

Thank you all very much for your assistance, it's truly appreciated.  My plan was to turn the heating off, wrap paper around the pipe below the valve, increase the pressure and wait for a while.  I managed the off and paper wrapping, but then got stuck - I don't know how to re-pressurise the system.  I got the manual out - which says to call the allocated 'competent person', so I opened the installation manual, also left with it and that doesn't identify which of the half dozen pipes does that.  Luckily a video on-line showed it and I have put the pressure back in to right in the middle of the okay zone.  I've put the heating back on to see what happens.

Sorry @Bendy_House - I started typing without seeing your edit.  I too was surprised by the amount of air gurgling last night, it's barely made a sound since I had the new boiler.   It's a Vaillant ecoFIT pure 830C.  Four storeys in the house, but only 2 served by the central heating.  I'll have to go and look for the inhibitor label, so I'll come back on that. 

Yes, there's a magnetic filter installed - I had that added a few years ago after a service.  Don't know when it was actually checked, but the boiler was serviced in early November, it was this that caused a problem with the old one that was difficult to fix due to age and shortage of parts and led to me deciding to have a new boiler.  New boiler installed late November.  Is the filter checked routinely with a service?

BooJewels

Don't appear to have any labels visible about inhibitors.

BooJewels

Having spoken to my son, he thought this was a perfect example of when to call in the experts and not try and fix it myself. The boiler is under warranty and for the first year, this includes the rest of the system, as this sort of problem often occurs when you put a new, more powerful boiler with older pipes and rads.

So, because I'm a  priority customer, they're coming out today  So I'll report back later as to how it turns out.  But I really want to thank you for the support and assistance today, I truly appreciate it.

Bendy_House

Thanks. Please keep us updated