Combi losing pressure

[Mrast]

Hi,

The last couple of weekends i have changed the pump in my boiler as the old 1 was failing then i changed the pressure guage the week after as it was blocked and wouldnt read at all (was stuck on 1.5 bar regardless of system full or empty)

Now i notice that the pressure is dropping. I filled it uo to 1.2 bar Sat afternoon and today its on 1 bar.

No central heating been on just hot water.

Now a bit of a conundrum, as obviously there is a leak of some sort somewhere although pipework/rads/valves seem dry, but as the guage hasnt been reading for the last year i have no idea if any pressure was being lost before! (never topped her up in 1 year though so id imagine not)

Now i drained the rads down through the usual drain cocks on 2 of my ground floor rads as per normal.

I then drained the boiler down via the circled tap thing in this picture
[DLMURL]http://i27.photobucket.com/albums/c197/thomo123/boilerdrain.jpg[/DLMURL]
It connects to the filling loop pipework and also tees out from the Central heating return pipe.

The service manual says this thing here in the picture is the drain off but its solid....
[DLMURL]http://i27.photobucket.com/albums/c197/thomo123/IMG_0413.jpg[/DLMURL]
[DLMURL]http://i27.photobucket.com/albums/c197/thomo123/IMG_0409.jpg[/DLMURL] - right hand side

Have i drained it from the wrong thing and caused a problem that could be relating to loosing pressure?

If i press the pin in the expansion vessel air comes out and not water but i havnt re-pressurised it yet as i couldnt get any leverage from the foot pump (got a guage on it) due to the awkwardness of the boiler location. (only pressed pin in for split second once)

I read around about people saying not to drain via the PRV - i dont think i have though? The PRV is the white knob on the right is it not and has a single pipe attached to nothing else running out the wall.

Could i have not fitted the pump correctly? (would see water coming from boiler though right?

Anybody that can offer anything to me i am appreciative off. I am fairly technically minded and am able to check stuff (bar gas of course), as no gas was involved thats why i did the pump and guage myself.

Boiler was "serviced" only 3 weeks ago. (do wonder if a service involves more than just cleaning out the heat exchanger!?)

edit - Boiler is a Vaillant Turbomax Pro 24e

Kind Regards

 

[stewm]

Hi well your in the thick of it, but when checking pressures was the boiler at the same temps as higher temp will show higher pressure, and recheck the safety valve for leaks as always a favourite.

 

[Mrast]

Hi Stewm - yes pressures have all been read when the boiler is "cold".

 

[aggis]

You've drained the boiler so it may have bled some air out of the auto air vent after refilling & using.
Top it up, 0.2 bar drop is very small, also worth checking that the auto air vent isn't weeping.

 

[stewm]

yes the drop is small and system can still be bleeding itself, bear with it as I dont think you have done anything wrong with the pump.

 

[Mrast]

well i topped it up to 1.5 bar 6pm last night and will monitor it over the next few days - it had lost some this morning tho 8am (only minimal but enough to see difference), only hot water for 1 wash up last night was the only use the boiler had as nobody was home.

Ill check the auto air vent tonight - its brand new with the pump though so hopefully it isnt playing up!
The service manual says it should be loose (1 or 2 turns) - are they full turns or just a twist of the finger?

 

[stewm]

Best of luck, and dont forget the pressure gauge is like a tupenny watch not very accurate.

 

[arran197]

I would run the heating for an hour, switch it off, let it cool, vent the rads and refill the system, as air can be a pain when trying to find out if there is a leak on the system if the AAV keeps releasing.