Pressure loss

Manuel Rathmann · 7 Apr 2021

Hi,

I have a 2 year old Viessmann Vitodens 050-W gas condensing boiler and a problem with keeping the pressure in the central heating system. When I pressurize the system to 1 bar and isolate the boiler the pressure holds so I assume there isn't a problem with the boiler itself.

When I pressurize the boiler to 1 bar and let it run normally with the heating on it takes around 1 hour to drop from 1 bar to 0. At the same time I lose around 170 ml in condensation and it takes me 30 sec. to fill the system up from 0 to 1 bar again.

Here is where I could do with some help from people who know far more than myself:
1) Am I on the right track thinking this clearly has nothing to do with the boiler itself and that I have a leak somewhere in the central heating system?
2) Given it only takes an hour to drop 1 bar and I need 30 sec for a refill am I correct in thinking the leak is fairly substantial? I am asking because if this is the case then it's fairly safe to assume it is somewhere under the floorboards on the ground floor - otherwise I would have seen water marks/damage somewhere

Thanks for your help,
Manuel

adlplumbing · 7 Apr 2021

check the blow-off pipe at the back of boiler on the outside, you have a water leak somewhere.

Manuel Rathmann · 7 Apr 2021

Sorry forgot to mention during that hour I lose around 170 ml of water coming out of the condensing pipe I believe? Not sure if that's the same as the PVR... In any case I guess 170 ml would not account for a 1 bar pressure drop...

adlplumbing · 7 Apr 2021

Get someone to check the heater exchanger,as it might have gone

Manuel Rathmann · 7 Apr 2021

So if the 170 ml of water are a result of a leaking heat exchanger that wouldn't account for such a pressure drop would it? Sorry for my ignorance but I can just about spell "boiler" and have a very basic understanding of how my heating system works

oldbutnotdead · 8 Apr 2021

Have you tried pressurising system and not running the boiler (to determine whether the pressure loss is heat related). If whole system holds pressure when cold you could have a leaking boiler.

Manuel Rathmann · 8 Apr 2021

Thanks for the response - meanwhile I've done exactly that: re-pressurized the cold system to 1 bar, bled all radiators and with the boiler off I lost 0.5 bar in 1 minute!! Suspect I have a massive leak somewhere under the floor. Of course everything is either tiled or covered in laminate

oldbutnotdead · 8 Apr 2021

Oh thats different (in yr first post you said isolated boiler held pressure). If pressure is dropping when the boiler is isolated (assuming pressure gauge is inside the isolated bit) then boiler is the prime suspect. Any water coming out of condensate or prv while its cold?

Manuel Rathmann · 8 Apr 2021

Ah sorry got confused - no the cold system test with the 0.5 bar drop in 1 min was indeed with the boiler connected/un-isolated but off...

oldbutnotdead · 8 Apr 2021

Ok. In that case yes you've got a leak. Have a look at easy stuff first (magnaclean, system drain points, bleed valves especislly any auto ones), rad valves, visible pipework.
Someone on here posted a great leak detection tip- get some smelly perfumr into the system & use your nose to track the general area

Manuel Rathmann · 8 Apr 2021

Cheers - good to know I'm on the right track. I've done all the obvious checks and with that amount of pressure loss it would be fairly obvious. Also got 3 bottles of nasty perfume for £3 from The Range but wasn't able to smell anything. Finally bit the bullet and got someone from a leak detection company to come out as I really don't fancy ripping up tiles/laminate willy-nilly. Apparently they use some tracer gas/thermal imaging or sound equipment to figure out where the leak is...

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Pressure loss

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