Boiler pressure drop - causes other than leak?

[nervous123]

As previously posted, I've noticed that the pressure on our sealed system - Vaillant Ecotec 630 boiler - drops rather quickly, about 1 bar over 2 weeks. I was led to believe that I must have a leak somewhere, and seeing as I cant find any obvious leak, it's probably gonna need a leak detection company who aren't going to come cheap.

Recently, though, it occured to me that the pressure never seems to go below 0.7 bar. Surely if there was a bona fide leak, pressure would drop to 0 bar, (or 0.3 and present a F22 message)? Could there (please!!) be some cause other than a leak?

Thanks a lot

 

[Boilerman2]

Lack of air in the Expansion vessel?
Expansion Vessel not big enough for the volume of water contained in the system?
A Leak!

 

[JamesRees05]

hi

ive recently had exactly the same problem!!

it was my expansion vessel, i at to have a new one fitted and now all is fine!

 

[nervous123]

but my system was only installed half a year ago! can the expansion vessel go so quickly?

 

[BingoBongo]

but my system was only installed half a year ago! can the expansion vessel go so quickly?

yes,check the prv isnt passing also maybe from either the exp vess or you over pressurising it

 

[mysteryman]

You need to check the pre-charge pressure in the expansion vessel with the system pressure at zero. If the boiler is downstairs in a 2 storey house, you need about 0.8 bar pre-charge.

 

[nervous123]

You need to check the pre-charge pressure in the expansion vessel with the system pressure at zero. If the boiler is downstairs in a 2 storey house, you need about 0.8 bar pre-charge.

Is that even if I don't have a Combi boiler?

I've checked in the loft and all I can see is a pipe going from the cylinder to the expansion vessel. The expansion vessel does not have a guage, dial or anything like.

To compound matters, it now seems pressure is dropping even faster, and lower. As a test I have turned off both CH and HW tonight - pressure was 1.3 cold about ten minutes ago - I'll have a look in the morning.

 

[bengasman]

but my system was only installed half a year ago! can the expansion vessel go so quickly?

Some more info would not go amiss.

 

[scatmanjohn]

If it never goes below 0.7 bar and you never get an f22 then leave it at 0.7bar

 

[nervous123]

but my system was only installed half a year ago! can the expansion vessel go so quickly?

Some more info would not go amiss.

Boiler: Vaillant Ecotec 630
Cylinder: Telford Tempest
Exp Vessel: Zilmet 110-Ultra-Pro (I believe comes as standard with the Telford cylinder)

(Have had CH and HW off for the last 15 hours. Pressure has dropped from 1.3 to 1.0 but has not dropped any further. However, last week when I have had CH on [but controlled by thermostat,] pressure has dropped to 0.7

 

[bengasman]

Is the whole system new, including rads and pipes?

 

[nervous123]

Is the whole system new, including rads and pipes?

No. 5 new rads and 7 old rads.

Pipework - Builder said he would replace all pipework where necessary, but I have no idea how much he actually replaced (and from other experiences with him, would bet he erred on the side of frugality)

 

[bengasman]

First suspects are:
Compression joints, rad valves, prv, ev, aav.