Vaillant Tubromax Pro pressure issues.

[Markjedi25]

My boiler loses pressure, over a period of a couple of days it will go down to zero. So i keep topping it up, however when we run the central heating the pressure will shoot up to about 2.5bar.

The boiler has been in the house since i brought it 6 years ago and we were told the boiler was 9 years old then. The pipe work is a mixture of soldered copper pipe and push fit connected plastic pipe. Something the previous owner had done, not sure if that makes a difference. I've checked the joints and cant see a leak.

Any ideas?

 

[Burnerman]

A pressure gauge that bounces around when the CH is on is usually due to the expansion vessel needing a recharge of air - see FAQ's for info on this.
If your boiler is losing pressure then there is a leak somewhere, so check the outsite PRV pipe for evidence of dribble first.
John