CH pressure system loses pressure

Sam Russell

My CH system is pressurised and loses pressure and has done since it was installed. Sometimes pressure drops over a week and sometime it takes a month. No leaks are apparent anywhere as far as I can tell.

The system is arranged into four zones, HW, upstairs, front and back. The back zone has under floor heating. Pressure drops from 2 bar to .2 bar. Everything appears to work OK. No water is leaving from the boiler vent pipe as far as I can tell.

Is it worth trying to find the link, or just wait till it gets worse?

Dtp1979

Sam Russell wrote: »

My CH system is pressurised and loses pressure and has done since it was installed. Sometimes pressure drops over a week and sometime it takes a month. No leaks are apparent anywhere as far as I can tell.

The system is arranged into four zones, HW, upstairs, front and back. The back zone has under floor heating. Pressure drops from 2 bar to .2 bar. Everything appears to work OK. No water is leaving from the boiler vent pipe as far as I can tell.

Is it worth trying to find the link, or just wait till it gets worse?

Get the coil of the cylinder checked

DGOBS

Is the 2 bar, cold fill pressure? If so, what does it rise tho under full load (all zones open and up to temp.)
Does it exceed 3 bar? If so, is the pressure relief valve passing?

If not, as above, have the cylinder coil checked, if that passes, have a pressure test done on the underfloor section

Sam Russell

The system I have is as follows.

The water system feeding showers, HW, and toilets is fed by a submersible pump in the attic set at 2 bar ( I think). This has worked fine for the last five years when it was installed. There should be little pressure difference across the HW cylinder.

The heating is provided by a Biasi boiler. The hot water system has four time clocks controlling the four zones. The HW timer is on for about 1 hour per day, the others as required.

The hot water cylinder is a huge insulated one that would be very difficult to do anything with as it is in a tight corner with a cupboard built around it.

The underfloor section has a single run of copper pipe under the floor with its own circulating pump.

There is no sign of water leaking anywhere.

Sam Russell

Been checking the system and pressure goes up and down.

I cannot find the pressure bottle anywhere so should I get one installed?

loyatemu

Apologies for thread hijack - Our system loses pressure as well, have to top it up every few weeks. We had a couple of leaking rads which I had repaired but the pressure still drops over time. Thing is, pretty much every house I've lived in with a gas system has been the same, the pressure drops gradually, top it up, repeat.

There could be a leak under the floor but if there is it's small and unlikely to be doing any damage (suspended floors...)
The boiler vent releases a fair bit of steam while running - would this be enough to affect the pressure in the system?
I believe the system has some anti-corrosion substance in it - is this being diluted by the repeated top ups?

Dtp1979

loyatemu wrote: »

Apologies for thread hijack - Our system loses pressure as well, have to top it up every few weeks. We had a couple of leaking rads which I had repaired but the pressure still drops over time. Thing is, pretty much every house I've lived in with a gas system has been the same, the pressure drops gradually, top it up, repeat.

There could be a leak under the floor but if there is it's small and unlikely to be doing any damage (suspended floors...)
The boiler vent releases a fair bit of steam while running - would this be enough to affect the pressure in the system?
I believe the system has some anti-corrosion substance in it - is this being diluted by the repeated top ups?

How often do you top it up?

loyatemu

Dtp1979 wrote: »

How often do you top it up?

recently every couple of weeks...

Dtp1979

loyatemu wrote: »

recently every couple of weeks...

Did you check the safety valve discharge. It's usually outside near the boiler.

lauraquirke

Hi there,
I'm having a similar problem with my boiler. It's a new boiler and has been losing pressure from the get-go. First, there were two rads not connected so they caused the pressure to drop but it's been one problem after another since then. Topped up the system one day and it'd drop down to nothing within a day. Plumber told us to attach water to system to try to flush out the leak, found one, fixed it but still losing pressure. Put pressure gauges on boiler and on heating to tell if the leak was inside or outside and, thankfully it's outside, but we still can't seem to get it fixed. Our plumber checked the boiler and found that the safety valve was faulty, replaced it and had the pressure set to 1 bar and it lost pressure soon after heating had run. It'll drop to half a bar when off, rise to just over a bar when system is running but within a day pressure when not running will drop below half a bar and the system will shut down. It's a new house and we bought it in good faith but this has been going on for 5 weeks now and there's no end in sight. Does anybody have any similar experience of situations like this and what we can do?

Dtp1979

lauraquirke wrote: »

Hi there,
I'm having a similar problem with my boiler. It's a new boiler and has been losing pressure from the get-go. First, there were two rads not connected so they caused the pressure to drop but it's been one problem after another since then. Topped up the system one day and it'd drop down to nothing within a day. Plumber told us to attach water to system to try to flush out the leak, found one, fixed it but still losing pressure. Put pressure gauges on boiler and on heating to tell if the leak was inside or outside and, thankfully it's outside, but we still can't seem to get it fixed. Our plumber checked the boiler and found that the safety valve was faulty, replaced it and had the pressure set to 1 bar and it lost pressure soon after heating had run. It'll drop to half a bar when off, rise to just over a bar when system is running but within a day pressure when not running will drop below half a bar and the system will shut down. It's a new house and we bought it in good faith but this has been going on for 5 weeks now and there's no end in sight. Does anybody have any similar experience of situations like this and what we can do?

1. Check your expansion vessel and air vents.
2. Replace your plumber
3. You don't get faulty safety valves.

When your system is filled to 1 and the heating has been on for 45 mins, what does the gauge read?

lauraquirke

Thanks for replying so quickly. The safety valve was releasing water, that's why he replaced it. When it's been on for 45 mins it reads just under 1.5, but when off it goes back down to .5 or lower (after which it'll cut out due to low pressure). The plumber is the guy who plumbed the house first day but I'm inclined to agree with you. At this rate I'll have to go back to the vendor with the problem and see what can be done. Thanks again.

Dtp1979

lauraquirke wrote: »

Thanks for replying so quickly. The safety valve was releasing water, that's why he replaced it. When it's been on for 45 mins it reads just under 1.5, but when off it goes back down to .5 or lower (after which it'll cut out due to low pressure). The plumber is the guy who plumbed the house first day but I'm inclined to agree with you. At this rate I'll have to go back to the vendor with the problem and see what can be done. Thanks again.

If a safety valve releases water, it's not faulty. It's simply doing its job. It's job is to release pressure at 3 bar. If your system is getting to 3 bar then it's usually an expansion issue. But again this is simple plumbing and id be worried if your plumber didn't know this or is forgetting to join rads. Check the cylinder coil too. It's not beyond possibility that it's leaking too. Rare but can happen

lauraquirke

Thanks for that. I'll have that checked too.