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

Bendy_House

BooJewels said:

Thank you.  I found the pdf of the installation manual myself last night, as it's easier to search than the paper copy.  I too read about the storeys, but as you say, not relevant to my issue in this instance.  Looking back I see that I posted that I had 4 storeys, but only 2 served by the GCH - I hadn't got the relevance until I read the manual - had the boiler been in the cellar, serving the 2 floors above it, it might need greater pressure.  Sorry, I answered the question without realising what was pertinent.

I had also read somewhere that the lines on the graphic were at 0.5 bar and 3 bar - but not sure where.  When I do hit that top right button twice (need to do it reasonably slowly), it does indeed show the pressure as a reading (thank you) and it's currently 1.8 bar and this would tally with being visibly about halfway between 0.5 and 3 - as it looks in the display.  In fact under the pressure number  it says something like 0,5 bar ~ 3,0 bar.   If the dotted lines were at 1 and 2, it would show as nearer 2 than it does.  Yet Vaillant themselves on their site say that it is optimal around 1.5 bar, which should be half way between the dotted lines.  So I'm a tad confused.

Having a series of bars with a couple of dotted lines is their way of trying to help...

According to their own instructions - and I think this is the most likely scenario - the two dotted lines will represent 1 and 2 bars, the former being the minimum a system is usually set to, and the latter the max you'd like to see it at.

0.5 is too low - most boilers are designed to shut down by this stage. And anything significantly over 2 bar is getting into 'triggering the PRV' territory, and also to be avoided. So, if you keep the pressure betwixt the two dotted lines, you'll be fine. My personal preference is to keep the pressure as low as you can above 'min' - mine is typically around 1.1bar - as this simply produces a bit less stress on the system.

BooJewels

I'd concur, I think my 1.8 is probably too high - if indeed it is at that. 

When I was filling it, I got to 0.9 bar on the display and the display went off - I was aiming for around 1 to start with, thinking I could add a bit more if it wasn't enough - so I stopped it at that point, because I didn't want to go too high, especially if I couldn't see what it was.  So I'm surprised it's indicating that it's 1.8 on the display.   To be that high, there would have to have been a significant lag between the pressure increasing and the display updating.  If the dotted lines are at 1 and 2, then my half way at 1.5 would actually make more sense.  I wasn't even expecting it to be that high.  At the time I was happy enough that it was in the middle of the ideal range, which it still is.

In future, if required, I'll add a bit and let it settle for a few minutes and see what the display indicates, then add more if required.  I'm making notes on this, as I hope I won't need to think about it for a while.

Bendy_House

Yes, seems a bit odd. But, as long as it's between the two dotted lines, I wouldn't worry.

If your system all settles down, with no more air needing to be expelled, and the pressure remaining constant, you can - if you like - lower the pressure slightly by bleeding a rad. But, really, little reason to.

BooJewels

Thanks @Bendy_House - I think once I get it sorted, I'll be leaving everything well alone.

At least I now know where it's leaking.

I set it up last night to try and see where the water was coming from by clamping some cheap blue roll paper (it's not perforated and changes colour when it's wet - useless for anything else) at various positions around the valve and up the side of the radiator, in case the leak was through the metal itself on that edge seam, although I didn't think so.  I put the heating off and set an earlier alarm to have a look whilst it was cold.  The one thing I didn't do was take the plastic head off the TRV, I think Mr Dyno had tightened it up very securely and I wasn't prepared to use more force.  I chickened out, sorry.

I woke at 04:30am anyway and was thinking about it, so got up for a look.  The 5 pieces of paper up the side of the rad were all dry, so that eliminated a high leak or from the bleed valve.  All three around the T of the valve were sodden, as was the towel wrapped around the pipe on the floor.  

I dried it off and waited to see where wet appeared.  After a few repeats of the exercise, I could tell it was coming out from below the knurled securing ring of the TRV.  Not an obvious drip, it just oozes out quite slowly.  The top of the ring stayed dry, the body of the T of the valve just became wet after 20 or 30 seconds.  I tried turning the valve to different extremes to see if the drip rate increased or changed, but it was difficult to tell from an ooze.

Presumably, this means it's leaking around the pin and then down out through the fitting?  Will this require a new TRV?  Is that a big job that requires draining the system?

FreeBear

BooJewels said: Presumably, this means it's leaking around the pin and then down out through the fitting?  Will this require a new TRV?  Is that a big job that requires draining the system?

Just the TRV body needs replacing - These are often cheaper when purchased as a complete kit. Not hugely expensive (about £15 from the likes of Screwfix). Yes, the whole system will need draining down unless you have access to a pipe freezing kit. Should take less than 20 minutes to change the body. A corrosion inhibitor should (must) be added when the system is refilled.

All in, you're probably looking at a couple of hours work.

BooJewels

FreeBear said:

BooJewels said: Presumably, this means it's leaking around the pin and then down out through the fitting?  Will this require a new TRV?  Is that a big job that requires draining the system?

Just the TRV body needs replacing - These are often cheaper when purchased as a complete kit. Not hugely expensive (about £15 from the likes of Screwfix). Yes, the whole system will need draining down unless you have access to a pipe freezing kit. Should take less than 20 minutes to change the body. A corrosion inhibitor should (must) be added when the system is refilled.

All in, you're probably looking at a couple of hours work.

Thank you.  Blast.  I won't be doing the work myself, this is way beyond my skill set.  I'll just go back to BG under the new boiler warranty, which includes the whole system for the first year.  It was them who sent Dyno Rod out on Friday, they must subby plumbing work to them.  2 hours - I'm just not happy about having people even in the house at the moment.

Is a corrosion inhibitor a liquid they add to the water when re-filled?  They were supposed to do a power flush and put new liquids in when they installed the boiler, but I was a tad concerned at how dirty the water was that came out of the rads I bled this week.  I was sort of expecting it to be cleaner?

FreeBear

Dyno-Rod is part of BG, so no real surprise they got the call.

Yes, a corrosion inhibitor is a liquid that is added when the system is refilled. It should always be added when ever the system is drained down.

Bendy_House

BooJewels said:

Presumably, this means it's leaking around the pin and then down out through the fitting?  Will this require a new TRV?  Is that a big job that requires draining the system?

Well done. Yes, I think you've sussed it.

Ok, time to be brave!   To remove the TRV head, first turn the head up to 'max' - 5. That releases the pressure of it trying to push down the pin.

Now grab that collar firmly, and unscrew it anti-clockwise as you look down at it from above.

If it's tight, then grab the TRV head (not the turning knob bit, but the plastic body just above the collar) in one hand and the collar in t'other. Get some steady anti-clock turning force on the collar, whilst rocking - oscillating - the TRV head back and forth (it'll only move a couple of mm each way). This should help release the collar - every time the head body moves anti-clock, the collar should move with it.

Once off, confirm where the leak is from.

It'll most likely be from around the pin, where it disappears into the valve body. In which case, you should only need to tweak that smaller brass nut - the one the actual pin comes out of - a tiny onesixtyforth of a turn. Under that nut is a rubber washer that the pin comes through, and which seals the system water inside. By slightly tightening that 'gland' nut, you are simply squashing that rubber washer a teeny  bit, so it goes more 'flat' and seals a tiny bit better against the pin.

Or, call the guys out again...

Bendy_House

BooJewels said:

They were supposed to do a power flush and put new liquids in when they installed the boiler, but I was a tad concerned at how dirty the water was that came out of the rads I bled this week.  I was sort of expecting it to be cleaner?

That's of greater concern.

They probably did do a 'system clean' when they replaced the boiler (it's actually a warranty requirement), but some old and well-sludged systems can still retain quite a bit of gunk, stuck firmly to the bottoms of rads and pipework. That's why a magnetic filter is also a 'must'.

Yes, the water should look pretty clear, but some inhibitors can add a slight brownish tinge to it, which can be misleading! But, the way to check is to open the mag filter and check what's inside.

BooJewels

Thank you kindly both @FreeBear and @Bendy_House for your patience in explaining things to me, it's truly appreciated.

I have already got a return visit booked via BG tomorrow.  My main reason for trying to identify the point of leak for myself was to try and cut down on the 'trial and error' aspect of someone visiting for a few minutes and trying to find it - when it's not evident when the system is warm.  I did explain what I'd done to identify where I thought the leak was on the phone, but at weekends, I think the answering service diverts to an overseas call centre and I think he just wanted to book an engineer and he either wasn't listening or didn't understand what I was saying.  So I'll explain it again tomorrow when the engineer rings to say he's en route.

I'll ask tomorrow for them to look at the mag filter and about the quality of the water - I'm not even going to try, it's about 11' off the ground and in a corner, above the boiler, so I'm just not even going to attempt climbing that high, leaning over the boiler trying to even reach it.  At 4'11" I just don't have the arm reach for tasks like that.  I did however remember that they filled in the commissioning report in the installation manual and it states that they used F3 system cleaner and F1 inhibitor.

Plumbing is one of those areas where it can get messy very fast if you get it wrong - I'm just not prepared to risk it.  But I'm happy to know where the leak is and that it can be either tweaked to tighten against the O ring, or possibly the valve bit replaced.  So, as such, that answers my original questions.