Needle dropping on pressurised CH system

[Ula NI]

Hi all, thanks for reading this.
We wanted to refurbish the bathrooms and got a few bathroom guys out to quote - one checked our boiler room (oil burner is inside house beside water storage/valves/pressurized system) and said our pressure appeared to have dropped and therefore we must have a leak somewhere???
We had boiler serviced a few months back and the system was re-pressurized then (we have noticed before that the needle moves from 2 and drops nearer to 1).
Bathroom guy didn't seem to have any solution as he was just quoting for bathroom at the time and suggested we get it fixed.

What do i need to do, who do i get and what am i telling them?
I've seen no signs of leak anywhere??
Obviously i need to get this sorted before/while getting the bathroom done.

Thanks for any advice.

 

[craig51]

Call a gas engineer and tell them the pressure is dropping.

In he meantime turn the heating off and let it go cold. Repressurise it back to 1 bar and turn the heating on. Sit there and watch the gauge and tell us what it doesn't over say 10-15 mins.

 

[avonmouth]

It only takes a small leak over a period of time to drop the pressure so check out all the rad valves first.Also check out the blow off pipe(prv) that terminates outside.It could be the expansion vessel but check for leaks first.

 

[Ula NI]

Thanks Avonmouth, i'll go check them.

 

[Ula NI]

I've checked all rads, no leaks, and outside pipe is bone dry.
Any other suggestions??

 

[Ula NI]

Craig51 it's oil fired ch. It's a zoned ch system where the water is constantly hot. I haven't had the central heating on in several months, no need. The system was really pressurised about 6 weeks ago and is very slowly dropping.

 

[avonmouth]

I would think you have a very small weep somewhere if it takes that long to drop.

 

[Ula NI]

That's what I'm thinking Avonmouth. Problem is, how is it found?

 

[polesapart]

By careful observation. Look for traces of scale/stain where a leak may have occurred even if dry to the touch now.
Rad valves, pump valves, zone valves, boiler connections generally, AAV at boiler if there is one.

Some advocate injecting cheap perfume into system and sniffing.

Most likely a slightly loose compression or union nut at one of the above locations or AAV.