Replaced PRV and still leaking

[chris watkins]

Yes it could in theory as it is an old enamelled steel type cylinder which I bet has not had the anode replace. If the internal heat exchanger has rusted the higher pressure domestic water could be leaking into the heating water raising the pressure so the heating safety valve discharges at 3bar.
As per other, get a good G3 engineer in (& disconnect that filling loop as per Water Regs).

 

[Harvest Fields]

Yes it could in theory as it is an old enamelled steel type which I bet has not had the anode replace. If the heat exchanger has rusted the higher pressure domestic water could be leaking into the heating water. As per other get a good G3 engineer in (& disconnect that filling loop as per Water Regs).

The pressure in the heating doesn’t rise when off it drops.

 

[Best]

Should have a frost stat and that wouldn’t make any difference anyway as unless it’s inside the boiler would be the same

Think of a standard heat only boiler where’s the vent connection / tee normally in the airing cupboard

I know what you are saying, but even on an open vented system, I always put a prv on the system, - and straight off the boiler pipes. Normally only oil systems, but also some gas.
If an open system feed and vent froze in the attic, the prv would be needed

 

[ShaunCorbs]

I know what you are saying, but even on an open vented system, I always put a prv on the system, - and straight off the boiler pipes. Normally only oil systems, but also some gas.
If an open system feed and vent froze in the attic, the prv would be needed

and if the prv froze

 

[chris watkins]

The pressure in the heating doesn’t rise when off it drops.

Safety valve is leaking all the time?
Sorry I will go back & read all the posts.

 

[Burger]

Just one more thing, the boiler has had all components completely replaced, all the PRVs and
The hot water tank expansion vessel have been changed in the last two years.
The only two things that have not been replaced in the past two years is the red expansion vessel next to boiler and the actually hot water tank itself, could it be the hot water tank itself gone wrong?

Everything points to getting it checked out by a gas safe heating engineer, and perhaps a different one/firm who replaced the prvs. The parts have been replaced in the last 2 years but it doesn’t mean they don’t require checking - as per previous posts every service.

 

[Best]

and if the prv froze

Then there would be no open pipe safety left.
But the boiler can likely be the last system area to freeze. Pipes leaving it in a garage are usually more vulnerable to freezing first, as would vent and feed in some roofspaces.
As you said, frost stat should save the boiler

 

[MHG]

Expansion vessel requires recharging or replacing

 

[David turner]

the PRV has been replaced twice in the past few months and this seems to cure the leak temporarily, however the leak is now worse and is clearly caused by a different problem. The pressure gauge rises quickly upto 3 bars, (we release the pressure manually) but then when the heating/water is off (boiler not running) it loses pressure to zero whilst it’s off. there is an expansion tank already fitted, this was replaced approx 7 years ago. Does it sound like the expansion tank needs replacing or could it be something else?

 

[David turner]

Your vessel requires charging or replacing if it won’t hold pressure also is the vessel large enough for amount of radiators that you have in property common problem is that plumbers don’t size up system correctly and fit undersized vessel additional vessel might be the answer to your problems.

 

[Stigster]

Your vessel requires charging or replacing if it won’t hold pressure also is the vessel large enough for amount of radiators that you have in property common problem is that plumbers don’t size up system correctly and fit undersized vessel additional vessel might be the answer to your problems.

Agreed, you can't cause a fault with an oversized vessel but an undersized one is likely to go wrong. If I was a betting man I'd say the same and that the vessel is undersized, lost its charge/failed or both.