Halstead hi ace losing pressure with water dripping from expansion pipe outside.

[hertzal]

My Halstead combi boiler started losing pressure last week & the engineer 1st thought it was the pressure vessel knacked,but on closer inspection said it was due to topping the pressure up to 1.5bar instead of 1 & he pumped some air into the pressure vessel with a hand pump & left,saying the boiler was now ok.The problem has now returned,with water dripping from the expansion pipe outside the house & loss of pressure from the boiler,which is in the loft of a semi.I would be grateful of any help with this problem.Thanks in advance,

Hz

 

[NozSpark]

If you are losing water out of the expansion pipe then there can only be two things happening..

1. You have excess pressure and the valve is operating to reduce it

2. The pressure relief valve is passing water when it shouldn't

 

[ProDave]

I'll bet it IS the expansion vessel.

I had the same on my unvented water tank. The bladder inside the vessel had lost pressure, so I pumped it up and it was okay for a short while but it soon started venting again.

If the air bladder is losing pressure then really that can only mean it's punctured.

To check this let all the pressure off and undo the hose connecting to the expansion vessel, then pick up the expansion vessel and shake it. I'll bet it's heavy and full of water.

Really your plumber should have checked that.

Actually a simpler test is just to use a car tyre pressure guage and put that on the valve on top of the expansion vessel. As a rough guide 3 BAR is about the normal pressure. What air pressure do you read with a guage. Worse still (as in my case) if water comes out of the air valve, then you know the bladder has burst.

They are not that expensive, so get him back, or preferably a different plumber and ask them to change the expansion vessel.

 

[hertzal]

Thanks for all the help,I,ll get someone asap as its going to get colder next week!

Regards Hz

 

[user 15807]

I assume you have sorted the problem by now! For future reference. Fill system up to 1.5Bar when cold/cool, bleed any air out re check pressure and turn on boiler. Watch pressure gauge as system heats up. pressure should rise by no more than 0.5bar maybe 1bar on a really large system.. If pressure rises dramatically, likelyhood is the expansion vessel has lost its air, very unlikely to help pumping it up, as if air leaked out, it will do again.