High boiler pressure, leaking overflow pipe. Help appreciated!

wadeo0

Hello,
Recently noticed our combi boiler's overflow pipe running a river down the side of the house. Looked at the boiler and the pressure is pretty high (about 3.5). Have tried a letting water out of the system by radiator bleeding but didn't seem to have any effect. Took the front off the boiler to try the pressure release valve - when turned pressure goes down but instantly shoots back up. There is also what looks like a small leak (and some rusting) around the bottom of the valve piping where it joins the chassis of the boiler. Other things I noticed are when taps are running pressure goes down to around 2.5ish, but goes back up when tap is turned off, can also hear a sound when I put my ear to the boiler - almost a hissing which sounds like water running through the system. Boiler is Vokera Compact 24.

I have very limited knowledge of this stuff but from reading up online it sounds like there could potentially be a leak that is allowing mains water into the system (would explain why pressure goes down when taps are on) and increasing pressure - would this come from a faulty heat exchanger? Any other ideas of what could be causing it? Hopefully moving out soon so hoping it isn't too much of a pricey one to fix!! Currently got a hose attached to overflow outside running into a drain so it doesn't flood the patio but will call plumber tomorrow, just wondering if anyone on idea has any other ideas.

Cheers in advance for any info!

payless

Is your filler loop open or closed ?

wadeo0

Thanks for the reply! It is closed. I also unscrewed the filling loop hose and that did not reduce pressure.

Ectophile

It could well be a leak in the heat exchanger, letting mains water into the heating system. If you can turn off the mains water feed into the boiler, it would stop the leak, but you'd have no hot water any more.

wadeo0

Ectophile wrote: »

It could well be a leak in the heat exchanger, letting mains water into the heating system. If you can turn off the mains water feed into the boiler, it would stop the leak, but you'd have no hot water any more.

It does seem like this. For example, if I run the tap for a while I can get the pressure right down but then as soon as I turn it off the dial ticks back up and it is back in the red after about 5-10 seconds. The outside leak also stops when the tap is running. Any idea how much a heat exchanger would be to fix?

I can live with the leak for now without losing hot water, I've just attached a piece of hose to the overflow pipe and am running it into a drain so it doesn't soak the patio overnight!

matelodave

A replacement heat exchanger for the Volkera 24 is around £200 ( https://www.dhsspares.co.uk/product/vokera-10021419-heat-exchanger-1531555?gclid=CjwKCAiA0svwBRBhEiwAHqKjFkoN98tGvzm0yWx0XbsYnrq6_JsUDucsq5FoT6OIYu9BsGEJx0j_sRoCuKQQAvD_BwE ) plus the cost of fitting

If you are on a water meter then you'll be paying for all the water you are losing. You should get it sorted out as soon as possible

wadeo0

matelodave wrote: »

A replacement heat exchanger for the Volkera 24 is around £200plus the cost of fitting

If you are on a water meter then you'll be paying for all the water you are losing. You should get it sorted out as soon as possible

I'm not on a meter but I realised last night that the boiler has it's own stopcock, so leak is now stopped while I wait on repair! Thanks for the link!