Long term pressure problem.

[Jmills]

Hi all

a quick back story. My pressure has been dropping on my system for 6 or so months. It originally needed topping up every few weeks to needing topping up every day.
we have a BG homecare policy and several engineers have come out, mostly scratching their heads and leaving.
the last guy changed the expansion valve and prv valve, we hoped that had cured it. But here we are 48 hours later and the pressure has dropped to empty again.
Any advice would help us as this has been going on for months. I also can’t see any visible leaks.
Jamie.

 

[EvilDrPorkChop]

What boiler is it?

It's probably your heat exchanger leaking internally and going down the condensate drain.

 

[Jmills]

What boiler is it?

It's probably your heat exchanger leaking internally and going down the condensate drain.

it’s an Ideal boiler. There is a copper pipe on the side of my house(the same level as the boiler) that I notice water coming out of sometimes.

 

[steadyon]

Assuming the exterior copper pipe is the pressure relief outlet for the boiler, then:
1. The pressure relief valve inside the boiler is letting water past because:
1a. It has failed, and is just letting water past before reaching its normal level of 3 bar pressure before opening.
1b. The pressure is rising to 3 bar when hot, the relief valve is opening, resulting in reduced pressure when the water cools. If this is the case, likely to be a problem with the boiler's internal expansion vessel.
2. Once the pressure relief valve has operated, they have a habit of not re-sealing properly, so may need replacing no matter what the primary cause.
3. If you can do it, try the following on a radiator in a relatively little used room:
3a. Turn off the valves at both ends. Count the number of 1/8th turns need to close the lock shield valve (the non-TRV) one, so that you can reset it t the same point later.
3b. Open the bleed screw.
3c. Slacken the nut between the valve and the radiator (NOT the nut between pipe and radiator) and drain out as much water as you can. Lots of old towels, baking trays, buckets. The water may be very dirty, so don't get it on the carpet!
3d. Re-tighten the nut and the bleed screw. You now have a radiator full of air, which will act like and expansion vessel for a while.
3e. Re-open both valves on the radiator.
4. Run the system. If it doesn't lose pressure, or the pressure loss is much slower, then the expansion vessel inside the boiler needs attention and possibly replacing.

 

[EvilDrPorkChop]

It sounds like your pressure relief valve is dripping, which i'm surprised BG hasn't investigated more.

However if it's an Ideal Logic, and around 6/7 years old the main Heat Exchanger will have failed and be leaking internally and going down the drain - which will be your pressure loss. Common issue on this boiler.