Boiler Constantly Losing Pressure

[Niks10]

Newbie here so go easy.

My Ideal HC24 boiler is constantly loosing pressure and I have to topup the pressure by opening bypass loop several times a day.
Obviously it needs fixing.
There is no visible leak in the pipework and pressure relief valve is not discharging anything outside.

I suspect it is something to do with pressure vessel (or any other part of boiler) which hold the pressure i.e. water that is leaking.
Is this an easy replacement (obviously by Gas Safe Engg, not a DIY for myself)?
And any approximate cost involved?

 

[andytw]

Hi,

If the loss of water is related to the expansion vessel, then you will be losing water out of the pressure relief valve which you say are not. Fasten a plastic bag over the relief valve outlet to be sure. If it is not coming out of there then it is not the expansion vessel.
Another check is to fill the system, at cold, to 1 Bar and then see what pressure it goes to when hot. Should go to no more than 1.5 or 2 Bar tops.
Report back.

andytw

 

[Niks10]

Thanks for reply.

water is definately not coming out of relief valve.
The problem is of boiler loosing pressure (from 1.5 bar to 0 in matters of hours) even when boiler is not in use i.e. no CH or DHW demand.
Am I missing something here. Is it not related to expansion vessel or any other holding area of boiler?

A portion of my lounge floor feels warm when CH is on, could it be leaking there? I always thought that was due to no insualtion on pipe (assumption).
Feel no wetness anywhere. If there was leak you would see some sign on floor or side walls etc for wetness.

Pressure does not go down when boiler is in use.
It only starts to go down when boiler is not operational. and in matter of a couple of hours it is down to 0.

 

[SpecialK]

Switch your boiler off and isolate the heating circuit using the valves underneath.
Leave it for a few hours and check pressure guage. Has it dropped? If not turn valves underneath back on - Does the pressure drop?

 

[Niks10]

Right, switched off the boiler, could not isolate any valves as suggested as they are impossible to operate. And boiler still lost from 1.5 bar to almost 1 bar in less than an hour.
When boiler is switched on but not in operation i.e. no demand for CH or DHW, the boiler makes some cracking sound.

Also can you tell me generally are central heating pipes buried in the floor underneath concrete or just below flooring board?
If they are buried underneath concrete I should not feel warm flooring (which I do when CH is in operation).
So if they are not buried underneath concrete and just under flooring board, is it relativelt easier/cheaper to replace/repair pipework and flooring?

 

[SpecialK]

Depends if you have concrete or wooden flooring?

You need to get the isolating valves working so you can find out if its the boiler or heating pipes/rads leaking....Try with a large flat screwdriver and rock them back and forth.

 

[Niks10]

Flooring is wooden...but I guess underneath will be concrete, looking at the floor/wall joint.

I have manged to isolate cold pipe circuitery, Hot pipe is too difficult, almost like the needle screw is welded to the valve and when I tried harder the screw started to bend, so I gave up.

In matter of minutes the pressure has dropped, i.e. no pressure in and still pressure guage is going down. I can now feel the hot water pipe going totally cold, almost same temp as cold water (it was hot as normal, before I switched off and Isolated inlet system, and it was hot few minutes later as well).

So when pressure is leaking from cold to hot and hot is not isolated we still have both possibilities, i.e. pipe work under floor leaking or boiler leaking or may be both.
Or should pressure not go from cold to hot side in any circumstances when there is no demand for CH or DHW and boiler is switched off?

Any other ideas.