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Discuss Immediate Loss of Pressure in Sealed / Pressurized Central Heating System in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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ashimashi

We have moved into our current home a few months ago. It's a very old house with relatively haphazard plumbing. Things worked fine until recently when I noticed that the pressure in the sealed system is on 0.5bar and it's not heating the upstairs radiators.

Got a plumber that had done some work on this house before, and he said there was no filling loop, he connected a pipe in the attic to connect mains system to the sealed system and repressurized it.

Looked ok for a couple of days but the system completely failed yesterday, and now when you repressurize it it goes back to zero bar almost immediately (as soon as you close the filling loop).

Plumber says this is definitely due to a leak. I find it a bit strange though, as: a) It has to be an absolutely huge leak if it looses that much pressure instantly, and b)there was no problem with the system and it wasn't losing any pressure (steady at 0.5bar) until he fiddled with it!

Based on that, can anyone think of anything that your man had done to screw it up, or is it really a leak that coincidentally appeared after he did the work a couple of days ago?

There are no signs of leaks anywhere in the house btw, he thinks it's downstairs and wants to dig up the floors!

Any advice would be greatly welcome. Not the best time of year to be left without central heating!
 
I'm sure someone will help on here but don't go blaming the guy who has tried to help :)
 
I won't blame anyone :)

If you are referring to me thinking the plumber may have done something wrong: I don't know him and TBH haven't heard great recommendations about him. The only reason I got him to take a look was the previous owners said he knows the house and it's systems! Otherwise I would've used my own trusty plumber. That's why I don't have confidence in him, especially considering the way it's losing pressure and the fact that it happened straight after he reconnected the filling loop! It can well be a coincidence though, and I'm open to that idea :)
 
no discharge from PRV at all, assuming that what I think is PRV is PRV: a red twistable valve at the end of a pipe that lets water out when I twist it and the pressure drops by doing so!
 
Ok in order for all on here to help info is needed.

If the system you are dealing with is a combi system ? Why was a second filling loop fitted - there has to be one always when the system is new. Go find the original filling loop and see whats happening to it. Anybody else got other ideas ?

centralheatking
 
The water must be discharging through the relief valve or else you have a leak somwehere.

Check the pressure in the expansion vessel (when the system is depressurised). It should be as stated on the size (usually 1 bar). You can do this with a car foot pump and gauge. If it is low, pump up to 1 bar.

If the pressure drops again, you will need to replace the valve in the end of the pressure vessel (spares from Halfords or any garage / tyre / bicycle shop). If this doesn't work then it's a new pressure vessel.
 
Having recently worked on one bg installed some combis with f/e tanks on old systems years ago as they were scared of splitting the original system under the pressure so no filling loop and a bugger to refill
 
Thank you all for the advice.

Here's some more info:

1. The boiler is a Glowworm Micron.
2. It is not a combi system. The plumber who connected the valve to connect the system to mains said it was there but not connected. I suspect the only connected it manually when needed.

I will check the pressure on EV tomorrow. If the EV is not working correctly could it be the cause of the immediate pressure drop? Does the water need to get out somewhere, and if not via PRV then is it certain that it's a leak?

What baffles me is can a leak be so big to lose pressure from 1.5 bar to 0 in seconds, and how come it happened only after the guy connected the system...
 
Hi,

Depending on the size of your heating system (volume of water) it can be surprising how small an amount of water needs to escape for the pressure to drop to zero.

I am not a gas installer however I do know it is not unusual for installers to remove a section of the filling loop to prevent the system from being accidently over filled, some consumers believe the instaler is trying to generate business, not true as many gas boilers come with a pressure stat that stops the boiler working if the pressure is too low or too high.

"and how come it happened only after the guy connected the system..."

There are such things known as coincidences, it is possible that a joint has failed under the increased pressure, having seen similar what we discovered could be better described as a weep than a full blown leak.

I suggest that you ask the plumber if he can do a pressure test (assuming the system is zoned).
 
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