MegaFlo pressure 0.3

[Lowhec]

Hello,

I have an unvented cylinder, Megaflo HE. The pressure drops from 1 bar to 0.4 over about 5 days then it will stay at 0.4/0.3 for at least a week (I usually then bring the pressure back up to 1). It never drops to 0. I have searched for leaks on all the radiators and around the cylinder.

Why does the pressure stop at 0.4/0.3 and doesn’t drop to 0?

Has anyone successfully used a sealant?

Has anyone used a leak finding service with success?

 

[Madrab]

That's probably the pressure level that whatever is leaking needs to leak, anything less and it's isn't enough pressure to push past, either that or the gauge isn't working right.

It's not your unvented that's leaking though, rather your central heating system. Leak sealer is not advised, it can cause more problems than it solves longer term.

 

[Lowhec]

Thank you Madrab.
I am having the cold water valve replaced as this is leaking badly. I have been told that this wouldn't cause the pressure to drop. Is that true?

 

[Madrab]

The pressure would only be directly affected by anything that's part of or connected to the central heating system (radiators/pipework/fittings/valves/boiler).

The cold water valve that feeds the cylinder with its cold water is separate to that.

 

[MeldrewsMate]

You have failed to grab the distinction that the water which comes out of your taps is not the water which goes through your heating system. To simpilfy things, try to think of there being a radiator inside your hot water cylinder (Megaflo HE); it transfers heat to the cold water to make it hot, but the boiler water does not mix with the bathing water.

Thus the pressure you read is not the pressure at the taps, it is the pressure of the water SEALED inside the heating system, and its purpose is to transfer heat from the boiler to the place where it is needed (radiators, underfloor heating, hot water cylinder, etc.). The leak is causing the pressure in the (not quite!) sealed system to drop - I refer you back to Madrab's comments above.

How did you notice the pressure had dropped to 0.3bar? Was it from a regime of reading it regularly, or perhaps because you had a warning from the boiler, or something else? An accurate answer to this could help to narrow down the source of the 'leak'.

 

[ianmcd]

post a pic of what you are calling the cold water valve , is it part of the filling loop

 

[Lowhec]

The boiler stopped working a few months ago. The pressure was down at 0, so I refilled to 1 and restarted the boiler. it went down again quickly. I found that leak when investigating the radiators. You can take the radiators off the wall they have plastic pipes that come out the wall behind the middle of the radiator - I don't know the proper name. the plumber just screwed this back and tested the heating - no more water came out.
So I have kept and eye on it since then and it seems there is still another leak. I have checked all the radiators and even gone round with a damp meter on walls and ceilings I can't find evidence of the leak at the moment.

I have attached a picture of the cold water for Ian

 

[ianmcd]

I am having the cold water valve replaced as this is leaking badly

Thanks for the pic, that is not a valve, it says on it that it is part of the valve set but it is not a valve as such, it is a pressure reducing valve and it regulates the water pressure inside your cylinder, the same water that comes out of your taps, that leaking is not causing your pressure loss in the heating system, what is above that ? could something else be leaking and dripping on to that or running down onto there ?

 

[Lowhec]

Hi
I have had the cold water combination and automatic air vent (there is evidence this has leaked before and was left closed) changed.
I have found a leak (hopefully THE leak) from the boiler.
The boiler is a Potterton Promax 15/2 HE Plus boiler (15yrs old). The leak is coming from the flow switch.
Do you know how much this would cost to fix? Will the whole system need draining to replace this part?
Thanks

 

[ianmcd]

as you have a sealed system it shouldnt need a complete drain down , but may need a partial drain down all depends on your system, only someone on site could make that judgement, sorry I never comment on price, it is what whoever does the job charges, but not a big job and the part is not overly expensive