My boiler keeps losing pressure

CPFC_79

Hoping someone can help me here as the last plumber that visited me couldn't work out what was wrong. 

I have a combi boiler - Valiant ecoTEC pro 28

For the past year the boiler keeps losing pressure and we are recording how often we are topping it up. Over the summer months when the heating is never on, we have to top it up approximately once a month. In the winter months when the heating is on we are having to top it up every 5 - 7 days. 

I can't see any visible leaks but appreciate they may be small and therefore not visible. 

I need to find a new plumber to work with me but any ideas on what this could be?

FreeBear

First question - Do any of the pipes run through/under a concrete floor ?

daveyjp

One easy job is to go around every radiator and ensure the bleed screw is fully tight.  

Flugelhorn

we have a similar boiler in a flat but was suddenly needing topping up rather more often - plumbers commented that it is actually only a small amount of water each time but that was definitely not right - they muttered about the expansion vessel but that was OK and then they went leak hunting.... there was one, fortunately under the floorboards so "reasonably" accessible and mendable 

ThisIsWeird

CPFC_79 said:

Hoping someone can help me here as the last plumber that visited me couldn't work out what was wrong. 

I have a combi boiler - Valiant ecoTEC pro 28

For the past year the boiler keeps losing pressure and we are recording how often we are topping it up. Over the summer months when the heating is never on, we have to top it up approximately once a month. In the winter months when the heating is on we are having to top it up every 5 - 7 days. 

I can't see any visible leaks but appreciate they may be small and therefore not visible. 

I need to find a new plumber to work with me but any ideas on what this could be?

What do you mean by 'topping up'? Ie, what pressure do you top it up to, and what does it fall to?
And, what does the pressure do at other times? Ie, does it fluctuate as the system heats up? Does it increase - if so, to what? 
And, what have you checked so far?
The first obvious steps - apart from monitoring what the pressure does in use - is to check the two exterior pipes for escaping water. These are the 22mm white plastic condensate pipe - which probably heads into a drain - and the 15mm copper safety discharge pipe which typically points to the ground.
The former will issue 'slugs' of condensate every few minutes utes when the boiler is in use, but nothing should come out when the boiler has been shut off. If you can position a cup under there, you can monitor this.
The latter - the 15mm copper pipe - should not have anything come out of it at all. Simplest way to monitor this is to rubber-band a clear bag over the end.
These are the basic layman's checks.
A step up from this, but only realistic in summer when you don't need your CH, is to isolate the boiler from the radiators. The 22mm CH 'flow' and ditto 'return' pipes have isolating valves on them as they join the boiler. These can be turned fully off, so isolating the boiler from the rads. If the pressure continues to fall asleep you use your boiler for DHW, the leak must be internal to the boiler. If the drop stops - but then does fall the instant a valve is reopened again - then the loss must be in the pipes and rads.

Markmywords

we had a similar problem and the gas safe engineer changed the pressure realease valve whcih seems to have helped. 

badmemory

Mine was leaking within the boiler itself, from almost new, it went on for years & they never found it.  I just put a bowl under it & topped up the pressure.  I had the same problem with the one before.  Still they were both cheapos & lasted just over 30 years betweem them.  My current one is not a cheapo & thankfully has no leak either.

CPFC_79

Thank you everyone for your responses. 

@FreeBear - yes they do actually. The flooring throughout is concrete and the pipes are set in the concrete and there is parquet flooring on top. So basically completely inaccessible  

@daveyjp - good idea I'll do that later

@ThisIsWeird - so it drops under 1 bar and I get the F.22 warning on the screen. When I top it up I put it to about half way between the bars. Yes I believe it does increase as the heating comes on but I will double check that. Should it be increasing as the heating comes on?

There is a wet patch under the copper pipe so I have strapped a clear plastic bag around as you have suggested. 

One other point to note which might be relevant is that the Egg Timer Symbol (anti cycling mode) seems to activate a lot in winter.....not sure what is normal (how many times a day).

Again this is something I can monitor

FreeBear

CPFC_79 said: @FreeBear - yes they do actually. The flooring throughout is concrete and the pipes are set in the concrete and there is parquet flooring on top. So basically completely inaccessible

You're not going to like this, but..... Copper, when in contact with cement, corrodes. It is a slow process, often taking 10-15 years before pinhole leaks appear. You might be able to detect the approximate area where there is a leak with the aid of a thermal imaging camera after the heating has been running for an hour or two. The other way is to lift the flooring and look for damp patches.

If you don't want to do either of the above, isolate the boiler and hook a hydraulic pump (cheaper models available from other sources) to one of the radiators. Raise the pressure to 5-6 Bar and monitor for any pressure drop over say a week or three (best done during the summer). Any pressure drop will point to a leak in the pipes or possibly a radiator - Always worth wiping the bottom of a radiator just in case a seam is weeping.

It is also possible that a TRV or lockshield is weeping around a seal or union nut. Again, a dry tissue is your friend.

ThisIsWeird

CPFC_79 said:

@ThisIsWeird - so it drops under 1 bar and I get the F.22 warning on the screen. When I top it up I put it to about half way between the bars. Yes I believe it does increase as the heating comes on but I will double check that. Should it be increasing as the heating comes on?

There is a wet patch under the copper pipe so I have strapped a clear plastic bag around as you have suggested. 

One other point to note which might be relevant is that the Egg Timer Symbol (anti cycling mode) seems to activate a lot in winter.....not sure what is normal (how many times a day).
Again this is something I can monitor

'Should' the pressure increase when the system heats up? Not really, because the boiler has an 'Expansion Vessel' inside it, which absorbs the expanding water, and should prevent a significant pressure rise.
A small rise is, however, perfectly normal, and not an issue. It all comes down to how high it goes. Just above 2 bar is usually acceptable, tho' not ideal. Anything approaching mid 2s or 3 is a problem, and indicates an issue, one that could ultimately lead to a system water loss = drop in pressure.
So, actual readings, please :-). 
What is the 'cold' pressure? What happens during the half hour after the CH has been turned on? How ultimately high does it get?
You mention a 'wet patch' under the copper pipe. I presume you mean the 15mm copper pipe outside which points at either the ground or wall? If so, yes, bag it - that could be a big clue.
The anti-cycle 'egg timer' is unlikely to be connected to your pressure loss. It is most likely functioning as it should.

CPFC_79

@ThisIsWeird - it's only a very small rise, it's been on for an hour and it's currently at 1.8.

I'll report back on cold pressure level in the morning as the heating won't be on tonight. 

Yes I mean the pipe that points to the ground....again I will inspect that in the morning

@FreeBear all the pipes in the floor are plastic, they were all replaced two years ago so I would hope no leaks yet! You mention "TRV or lockshield is weeping around a seal or union nut' is this where the rads connect to the pipes? So just inspect all of those and check no leaks?

Thank you both!