Topping up boiler, how often?

[Johntheo5]

The mains water was/is common to both boilers so maybe a clue in that, its hardly the pressure? but may be acidic?

 

[wedge69]

I'm sorry, I'm not sure what you mean

 

[terryplumb]

I'm sorry, I'm not sure what you mean

Neither am I !!!

 

[Johntheo5]

The PHEX must have a max design pressure but it would be highely unlikely that your mains pressure excèeds it whatever it is, if the mains water is acidic then it could cause pinholing of the plates and pressurize the primary side but any one of these scenarious probably unlikely.

 

[terryplumb]

I think you may have a leak on the system side.
Any pipework buried in concrete or in a void under flooring ?

 

[wedge69]

There's a bit that goes under the floor in what used to be the outbuilding but got converted in to living space, so I guess it could be that. Would the testing of the heating during the service have caused something to go pop?

I've got trace and access on the home insurance policy, but the small print suggests I need to give Vaillant a chance to rule out the boiler before I can get the insurance involved.

So I guess I'm going to be waiting until Thursday now. I'm not going to keep topping up the boiler as that's only giving it more water to leak!

 

[Johntheo5]

Oh yes, I forgot, the leak is outwards now!!,

 

[wedge69]

Are there any obvious tell take signs of a leak under the floor? To the best of my knowledge it's screed with tiles on top. There's no visible signs of dampness

I've also just double checked all radiators and they're dry

 

[Johntheo5]

Yeah, so I'm struggling to understand why I can't see anything!

I'm going to stop topping it up and not use the hot water or heating until it has been looked at. At least that way I'm not adding any more water that could be leaking out.

Any thoughts on what a boiler service could have triggered? Best case I'm hoping something has just been left untightened. Worse case, running the heating caused something in the pipework to pop, but as I said, there's no obvious signs.

Its possible even if unlikely that the boiler was topped up until the boiler PRV lifted at 3.0bar as there is no pressure reducing valve on that top up line, but then there would have had to be well over 4 litres drained back out to return the pressure to 1.0bar, 3bar pressure shouldn't have blown any joints anyway.

 

[terryplumb]

Simple test to establish if water is leaking from the system would be to top pressure up to 1.5 bar, then close the boilers flow and return valves,leave for 24 hours unused. If pressure still drops then it's highly likely the loss is from the boiler rather than the system. As the isolation valves may not fully close off ,it's not 100% conclusive though ,but it's a good indication.

 

[Harry Bloomfield]

They only put a small bottle in though and we have 16 radiators, so maybe need some more?

The entire amount, for a full system, is only a tiny bottle.

 

[wedge69]

I don't want to start messing with anything until Thursday when the guy is due to come back. Let's say he finds no issue with the boiler. Am I allowed to isolate it myself, or does that need to be done by someone who is gas registered?

Assuming the boiler holds pressure, is it ok to use the hot water in that instance?

 

[terryplumb]

Assuming the boiler holds pressure, is it ok to use the hot water in that instance?

Don't really understand that question. If you close the boilers flow and return isolation valves ( which you can do ,don't need to be an engineer) I wouldn't advise using the boiler for anything,leave it electrically switched off at least overnight to see if pressure drops.

 

[wedge69]

Don't really understand that question. If you close the boilers flow and return isolation valves ( which you can do ,don't need to be an engineer) I wouldn't advise using the boiler for anything,leave it electrically switched off at least overnight to see if pressure drops.

With it being a combi boiler, I thought of you were only isolating the central heating flow and return you might be able to still use it for hot water only.

 

[Johntheo5]

I would have thought you could since the EV and PRV and any internal by pass are still in the circuit but keep a careful eye on the pressure.