Central Heating leak/ pressure drop

[psarinuk]

Hi,

So I have a Ravenheat HE85T combi boiler (same as CSI85T) and the pressure seems to be reducing by ~0.1 bar every week. This is regardless of whether the boiler is in DHW mode only or DHW+CH mode.

I've checked/ tightened all rads and even looked inside the boiler but I can't see a leak anywhere.

I am now planning to book a conversion to Vaillant Ecotec Pro 28 boiler which is a straight swap after a power flush, so I presume the installer would not dig deeper for leaks.

I've also bought a Fernox F4 leaksealer but feeling a bit scared to use it.

The question is should I add the leak sealer before the boiler replacement so it can run around the system and seal the leak before this boiler is removed?

If the leak persists after new boiler is installed, would adding leak sealer invalidate the generous 10 year warranty?

Thanks for your advice in advance.

 

[Madrab]

Don't use leak sealer, especially if a new boiler is going to go in. In fact .... don't use leak sealer at all.

The Installer should mention any leaks out on the system isn't his responsibility unless it's agree before hand.

There should be a copper pipe running outside from the combi and then bending back to the outside wall, is that dripping? If so it needs a new pressure relief valve and investigation into why it lifted. Does the pressure rise significantly when the CH is on?

 

[psarinuk]

Hi Madrab,

The copper pipe at the wall is completely dry indicating no leaks at the pressure relief valve. It leaked around 4 years ago and I had to re-pressurise the expansion vessel.

The pressure does rise to ~2.3 bar when the CH is ON with the thermostat at 9 O' clock. I am guessing the expansion vessel has got some water again but how does that relate to leak/ pressure drop when cold?

 

[Harry Bloomfield]

Add a plastic bag, fixed with rubber bands, over the end of the pressure release pipe - that is a more certain way to spot leaks from that.

Make sure the expansion vessel is properly pressurised with air, via the valve and the diaphragm not leaking.

It doesn't need much leakage for a system to loose pressure - look around for any stains and wrap toilet paper around any you spot as a telltale. Check hidden pipes too, its not unknown for copper pipes to have pin holes.