System losing pressure

Katie Hellewell · 24 Feb 2016

Hi all

We have been having issues with our central heating/hot water for a few weeks now. It loses pressure really quickly (1 bar in a few hours). It loses this pressure even when the central heating and hot water are not on.

We have had Worcester Bosch out today to look at the boiler as it is still under warranty - they isolated the boiler from the pipes which confirmed that the issue is in our pipework, not the boiler.

All pipework is in studwalls/ceilings, except for two radiators on the ground floor (one under a floorboard/carpet floor, one under a concrete/tiled floor).

There are no obvious leaks anywhere in the house - as I mentioned, this has been an issue for a couple of weeks, so I think we'd have noticed if the leak was anywhere else.

I have had a bag over the pressure release valve for a week now and this is not leaking.

My questions are:
(1) Can we re-pipe these two ground floor radiators from the boiler rather than digging up the floors?
(2) Is there something else which could be going wrong here - maybe the expansion vessel? If we are losing so much water from the system, would the expansion vessel be leaking?
(3) Is our only option to go under the floor in each room?

Thank you in advance for your help.

dilalio · 24 Feb 2016

It doesn't necessarily take a lot of water loss to drop the gauge on your pressurised pipework. It could be evaporating/flash drying on the hot pipes or running down vertical pipes and disappearing!
Are all your ground floors concrete? Have you had any work done recently? Flooring, door bars etc? Check all rad valves to eliminate visible/accessible pipework.
If you do need to repipe due to hidden leak, you can do it surface mounted and box in, but it looks crap. There are leak detection companies that don't charge if they don't find the leak.

Katie Hellewell · 24 Feb 2016

Thank you very much for your help.

One of the floors is concrete (tiled over) and one is floorboards (carpeted over).

We have had work done recently, but not in either of those rooms.

All radiator valves are dry.

Do you think that the expansion vessel is faulty? Would there be visible water coming from this if it was at fault?

Thanks again.

dilalio · 24 Feb 2016

Is your ev not inside the boiler housing/case do you have a separate ev?

Katie Hellewell · 24 Feb 2016

It's separate.

Thanks

Katie Hellewell · 25 Feb 2016

Hi

The Worcester engineer isolated the boiler from the pipes, set the pressure to 1.5 and turned off the boiler. He said that if I lost pressure, it is the pipework at fault.

I have just been reading online about this and I think he is wrong - I think that if the pressure drops while the boiler is isolated, it is the boiler that is faulty.

The pressure has already dropped to 0.

Please could you advise who is correct here?

Many thanks

Madrab · 25 Feb 2016

If the gauge is on the EV and it's connected to the CH system pipework away from the boiler and that has dropped to 0 when isolated from the boiler then it's the pipework/rads. If the pressure gauge is part of the boiler and its isolated and that's lost pressure, then its on the boiler side.

dilalio · 25 Feb 2016

Katie Hellewell said:
We have had work done recently, but not in either of those rooms.

What work? Where?

dilalio · 25 Feb 2016

Madrab said:
If the gauge is on the EV and it's connected to the CH system pipework away from the boiler and that has dropped to 0 when isolated from the boiler then it's the pipework/rads. If the pressure gauge is part of the boiler and its isolated and that's lost pressure, then its on the boiler side.

+1.
If the engineer got this one wrong I'd be extremely concerned!!

Katie Hellewell · 25 Feb 2016

Thank you both. The pressure gauge is separate to the boiler, so sounds like it is in the pipework afterall. A shame as the boiler is still under warranty!

We had an extension with new radiators. We have already had two noticeable leaks in the new rooms but these were fixed two weeks ago and pressure still drops to 0 in a few hours. There are no other visible leaks anywhere in the house.

It's going to have to be one of these leak detection companies isn't it? Any idea of cost please?

Thank you again for your help.

AngelesPlumbing · 25 Feb 2016

Time to phone your local plumber?

Katie Hellewell · 25 Feb 2016

We've had plumbers out but they can't see a leak, so can't help unfortunately.

Is there anything I could be missing to check before I call out a (expensive) leak detection company?

Ltnman · 25 Feb 2016

I had the same problem a couple of years after the installation of a combi where the pressure would drop to nothing in the space of a few hours. Out of desperation I used a couple of bottles of fernox leak sealer http://www.fernox.com/problem+solving/how+to+sheets/repairing+leaks. As I had a magnaclean on the pipework I just isolated that using the taps that came with it, emptied the vessel and filled it twice with fernox. For me it worked and that was in 2011.

Katie Hellewell · 25 Feb 2016

Thank you for the suggestion - I'll give it a go tonight.

I have called a leak detection company about coming out next week in case the Fernox doesn't work, but I am concerned that I've missed something really obvious and we'll be stuck with paying a big bill to detect a leak that doesn't exist!

Could it be the heat exchanger (or would this have been identified when we isolated the boiler)? Could it be something to do with the hot water cylinder (I have read about coils leaking)? I don't think it's the expansion vessel as the PRV is dry.

Thanks again for your help.

Hugh Jaleak · 25 Feb 2016

If the leak was internal inside the boiler, it should have shown up when the boiler was isolated from the rest of the system, but if there isn't a pressure gauge on the boiler, you wont know if its dropped or not! What model of boiler is it and what type of system do you have? Cylinder coils can pinhole, but without isolating the cylinder from the rest of the system it is going to be virtually impossible to ascertain if this is at fault.

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System losing pressure

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