Boiler water pressure drop

Drew_30

Hi.
I have a valiant eco tec system boiler with unvented water storage cylinder around 3 years old
Lately the water pressure started to drop and throw up an error code on the boiler of low pressure firstly every few months then weeks I topped it up and now slowly it's getting worse to where I have to top it up weekly to 2bar.
I have found no leaks at all in the house no water no stains no leaking pipes
I've had a plumber check it over and said mechanically it's perfect and working perfect. He said there maybe a pin hole somewhere and until I find it he can't fix it.
There is no leaks in the pipe outside the house so it's not over pressurising the vessel and dumping it outside I just can't understand it at all any help would be appreciated
Thanks

nofoollikeold

If you can find a time when you don't need heating or hot water for, say, 24 hours:
1. Turn off boiler at mains.
2. Pressurise to 1.5 bar or thereabouts.
3. Isolate boiler flow and return pipes by closing the valves to the flow and return pipes under the boiler. These are the extreme left (flow) and right 22 mm pipes under the boiler.
4. If, after 24 hours, the pressure hasn't dropped, then the problem is in the heating / hot water circuit.
5. If the pressure has dropped, the problem is within the boiler.

Drew_30

Hi sorry for my late late reply
Since my post I've had a plumber charge up my pressure vessel that lasted 24hr
After that he changed my pressure vessel which cost a bit that. Made no difference after that I noticed for the first time water dripping the exit pipe outside the house so he changed the prv valve and now it. Lasts a day and half before I have 0.0 pressure
I have today topped it up to 1.8 bar and I've closed the. Flow popes to see what happens.
Do I look at the two guages the boiler one and the one in the loft on the filing loop. I presume if the boiler pressure remains but the guage on the loop has dropped its my system?,,
It's really bugging me as I tried to sort this before the cold weather and the systems only 4 years old

southcoastrgi

Where is your boiler located ?

missile

I had similar pressure drop, caused by a leak in the heat exchanger.

Drew_30

Kitchen and the water storage system in the loft

nofoollikeold

1. Assuming the boiler is in the kitchen, and the pressure gauge is also there, that's the only gauge you need to look at. The gauge by the hot water cylinder will likely be for the pressure in the the hot water system's expansion vessel, usually white or blue painted. If the gauge in the loft is on the boiler filling loop, its may be more accurate than the one on / near the boiler, but you should be able to use either.
2. As you say, turn the valves off, wait as long as possible. Then if the pressure has gone down before you open the valves its your system. If it drops immediately you open the valves its your boiler. But note, that some boilers have an internal (usually electronic) gauge, which may monitor the pressure on the boiler side of the valves, in which case internal boiler loss would be noticeable after the wait and external (system) loss after the valves are opened.

Drew_30

Hi I have just checked which is 24hrs with the pipes closed and boiler off
The guage on the filling loop on loft says empty
I turned the boiler on with pipes still closed and it said 1.5 bar and jumped to 1.9 when it kicked in but I turned it off straight away as the pipes are closed. I'll check again tomorrow.
What does this suggest?
Thanks for help it's really frustrating

Lgas

This indicates a leak in your heating system, not within the boiler itself.

Drew_30

Going leave it a bit longer and see if the boilers the same. Not going be fun finding it as its a bungalow and no underfloor pipes most pipes are on show and I've not seen anything so probably have check all. Through loft.
What is 2bar with of leak like small or big in volume?

missile

Drew_30 wrote: »

...
What is 2bar with of leak like small or big in volume?

A very small leak will cause pressure drop. I and my plumber searched but could not find any sign of a leak.

In my case only after the old boiler was removed did I find evidence of a small trace left on the heat exchanger.