Water blowing out of my pressurised system

[tundra]

Hi,

5 years ago I had new pressurised central heating system. I have been noticing over the last few months excessive discharge from the pipe outside.
When I look at the boiler etc. when the system is running there seems to be a permanent dribble downstream from 2 PRV's.
I know it could be one of those that could be faulty. So I tried the trick of manually operating them to try and clear anything and it made no difference.

In the past I also had issues with pressure loss, not so much now, so tonight I looked at the 2 expansion vessels. One blue one red.
When I push in the valve on top of them, the red one fizzies with pressure, but the blue one is totally silent?

So I can't decide whether or not the vessel is faulty or maybe the valve on top. Or whether or not it is still a PRV fault.

Can anyone help?
Thanks

 

[swbjackson]

The blue one is probably the expansion vessel for an unvented cylinder. These should be serviced annually by an installer with an unvented ticket.

 

[pipshady]

i m a bit confused as to why you have 2 expansion vessels, what the pressure gauge/gauges do when the system is operating? i must admit i d be thinking prv, especially as you ve fiddled witht them now, i d say they are more likely to leak! have you tried removing the top of the prv and cleaning the seat? it does nt always work, but worth a try, failing that get two new prvs and see what happens! (if you re still losing pressure i d say it was one of your expansion vessels, check the charge pressure on them)

also check the rest of your system for leaks, if you have any pipes buried in floors check for damp patches, make sure you have no leaks from the boiler!

 

[tundra]

The 2 vessels are in the airing cupboard next to the hot water tank. Could one vessel be for the heating and one for the hot water????
There is only one pressure gauge under the red one, which is by the fill loop, it tends to be just over 1.

To remove the top of the PRV I assume I will need to completely depressurise the system?

 

[pipshady]

mmm i ve never seen 2 expansion vessels on a system, not sure what a blue one would be but sure does nt sound like an expansion vessel, without seeing it i can t say, but yes you will have to completely depressurise the system to clean the prv.

 

[screech]

mmm i ve never seen 2 expansion vessels on a system, not sure what a blue one would be but sure does nt sound like an expansion vessel, without seeing it i can t say, but yes you will have to completely depressurise the system to clean the prv.

have you never seen a sealed system with an unvented cylinder that has an expansion vessel rather than an air bubble?

blue or white expansion vessels are generally used on unvented cylinders (potable water), red or silver vessels on sealed heating systems.

 

[pipshady]

thank you screech now you mention it i have seen unvented with white expansion vessels, never blue though! i try and stay away from unvented, i ve got the unvented ticket but i would nt be confident working on it! must ask my boss to put me on the course again!