Boiler pressure query

Britannia12345

Apologies for another thread on this subject as I searched many but couldn't find one that matched our problem. 
We moved house recently and I had the boiler serviced before we moved in. The engineer said it was all good and well maintained. 
Since then it keeps losing pressure overnight when the boiler is off. I've followed youtube videos to top up the pressure but I'm concerned over where the flipping water is going. 
I've checked the whole place for leaks and can't find anything. 
The only suspect thing we have is something I've never seen before. We live in a bungalow and the boiler is in a larder on an inside wall. The condensate pipe from the boiler goes into a tank on the floor of the larder and it is then pumped up to the loft and along a pipe to the outside of the bungalow and down into the drain. 
I asked the engineer about it as I had no idea what it was and he said it was all fine, just a way round putting the boiler on the inside wall. You can hear water dripping into the tank quite regularly but I'm not sure if this is normal or not as the condensate pipe in our old house was piped down into the kitchen and onto the sink waste pipe so you could never see just how much water was trickling down into it. 
Any thoughts? I'll have to get an engineer back in after the holiday but it's puzzling the hell out of me. 

Albermarle

It is normal for condensate to drip from the boiler, when the boiler is running. This is unlikely to be the source of your problem. 

Can you supply some figures. Such as what is the normal pressure during the day and what is it after it has gone down overnight? Does it not lose pressure at all during the day/when the boiler is running ?

Britannia12345

It sticks around 1 when the heating isn't active but when the rads kick in it goes up to about 1.5. When it goes off overnight it's somewhere around 0.25. 

Rodders53

Combi boiler? or System boiler with HW tank?

Check the pressure relief valve vent of the boiler (tho that should only operate at circa 3 bar) but once operated they have an alleged tendency to keep dripping.

That vent is usually directed outside as it can be scalding hot water/steam  --- but may go into the same 'sump'/ tank via a visible tundish arrangement... Look for drips from such a tundish ?
Usual advice is to place a plastic bag around the external vent pipe with an elastic band to capture the evidence of such drips... not sure that would be wise if inside the dwelling.

Probably the pressure vessel needs re-pressurising / checking (red if external to boiler, likely within the housing), and maybe the PRV replaced, too?

Water is leaking somewhere if you keep topping it up (and diluting the inhibitor).  That leak just needs locating, first.

ThisIsWeird

Britannia12345 said:

Apologies for another thread on this subject as I searched many but couldn't find one that matched our problem. 
We moved house recently and I had the boiler serviced before we moved in. The engineer said it was all good and well maintained. 
Since then it keeps losing pressure overnight when the boiler is off. I've followed youtube videos to top up the pressure but I'm concerned over where the flipping water is going. 
I've checked the whole place for leaks and can't find anything. 
The only suspect thing we have is something I've never seen before. We live in a bungalow and the boiler is in a larder on an inside wall. The condensate pipe from the boiler goes into a tank on the floor of the larder and it is then pumped up to the loft and along a pipe to the outside of the bungalow and down into the drain. 
I asked the engineer about it as I had no idea what it was and he said it was all fine, just a way round putting the boiler on the inside wall. You can hear water dripping into the tank quite regularly but I'm not sure if this is normal or not as the condensate pipe in our old house was piped down into the kitchen and onto the sink waste pipe so you could never see just how much water was trickling down into it. 
Any thoughts? I'll have to get an engineer back in after the holiday but it's puzzling the hell out of me. 

Since the boiler is located on internal walls, with no easy access to an outside wall or drain, the condensate produced in use needs to be pumped away - normally it would drain away by gravity c- ie a downwards-sloping pipe.

And, yes, during use, you'd expect the condensate pipe to release condensate into this 'tank', usually in 'slugs' or 'glugs', as it empties from the boiler via a syphon. Ie, it wouldn't be a steady trickle, but more the odd drip and then a slug of water, followed by the odd drip again as the pipe empties. Repeat ad nauseam.

However, the condensate pipe should only release these slugs during use, so a fair while after the boiler has shut down for the evening - say a good half-hour after - there shouldn't be any significant release at all. The odd drip, yes, from liquid coating the pipe, but no 'slugs'.

Is there some way to monitor this? Can you see where this pipe empties into the tank? Can you lift the lid and observe? Could you even float a wee plastic cup in there, so the pipe directs into it?

If water is being released after the boiler stops producing condensate, then what you'll be seeing is 'system' water, and that will usually indicate a pretty serious boiler issue like a cracked main exchanger - and a pressure drop.

Only a theory, of course, and it needs testing. Why would this only happen when 'cold'? Sometimes such a crack will be effectively sealed shut when the boiler has heated up. 

The other laypeep's check is the safety discharge pipe as mentioned above. This will either head outside to deposit any excess safely, or it may do so via the same tank as the condensate - in which case there would be a 'tundish' installed so you can monitor any release.

Could you take some photos of your boiler, please, and also the associated plumbing underneath it?

FreeBear

Britannia12345 said: Since then it keeps losing pressure overnight when the boiler is off. I've followed youtube videos to top up the pressure but I'm concerned over where the flipping water is going. 
I've checked the whole place for leaks and can't find anything. 
The only suspect thing we have is something I've never seen before. We live in a bungalow and the boiler is in a larder on an inside wall. The condensate pipe from the boiler goes into a tank on the floor of the larder and it is then pumped up to the loft and along a pipe to the outside of the bungalow and down into the drain.

I assume this larder is adjacent to the kitchen - It may pay to route the condensate pipe in to the kitchen and plumb it in to the sink waste. This would avoid having to pump the condensate outside (pumps can will fail).

Now for a couple of questions.. Do you have concrete floors, and are any of the pipes for the heating system buried in the floor ?

If you have copper pipes buried in concrete, the cement will slowly eat away at the copper and eventually cause leaks. Lifting flooring often reveals damp patches pointing to leaking pipework. Unfortunately, digging up the floor is messy, and won't stop leaks appearing elsewhere.

Britannia12345

We do have concrete floors. I'm not sure where the pipes come from. Will have to have a look. 

Britannia12345

Scary pipes under boiler......

Rodders53

Oh dear oh dear oh dear

The PRV pipe is that copper one sitting alongside the white plastic condensate pipe and into the larger diameter drain pipe into the collection tank.

No easily visible way to see a PRV release or slow drip.. i,e, a tundish.

Lifting off the lid of the tank may show something useful, I hope

badmemory

When my last 2 boilers did this the leak was actually in the boiler.  Just every so often it would lose pressure as the leak was small.  It took a long warm summer to actually find it as hot water dripping on a hot pipe just evaporates.  New boilerman & new boiler, "did you know your old boiler was leaking".  My new one does not, over 2 yeats & nothing even to bleed from the radiators.  I do sometimes wonder what I paid the previous installers for annual services for though.

Britannia12345

It was off again this morning so I'll have to get an engineer in.