No boiler pressure but no visible leaks - please help!

Discocat

We came home on saturday night to find that our Central Heating had gone off and our boiler pressure was at 0. We put more water in the system and went around the house bleeding all of the radiators. Still, the pressure dropped to 0 within 5 seconds. Even with the tap on, the pressure never raises more than the first line (about a fifth of a bar). We called an emergency heating engineer out who said that it wasn't the boiler as when the pressure was high enough it fired up. He couldn't find any leaks and as he was charging £150 an hour(!) we sent him home. We had another engineer come out today who again tried putting water in the system. He confirmed that there was no leakage from the boiler pipe outside but he had no idea where the water was going.

Bear in mind that 100s of litres of water have now gone in to the system and there are no obvious leaks either within the house or around the exterior. The engineer said that there was nothing more that could be done as it must be leaking under the concrete floors.

If this is the case who do I need to get out to take up the floors to look? Plumbers don't want to do it and neither do heating engineers... what kind of contractor do we need to get to help us solve this mystery?

I really look forward to some help as we are freezing cold and miserable with no heating or hot water!

AlistairDarling

Hi there

sorry to hear about your heating woes, if your boiler pressure is falling to zero then you almost certainly have a leak. Just 'cos you can't see it, doesn't mean it isn't there. I had the same problem in January and it took about 4 days for the stains to appear in the kitchen ceiling.

Bottom line, a central heating system is a closed loop. If your pressure is falling then that water is going somewhere. How big is your house? have you done any DIY lately that might have nicked a pipe?

If you can, start lifting floor boards and look for moisture/gallons of stray water. DON'T REPRESSURISE YOUR BOILER UNTIL YOU FIND THE LEAK

Good luck

Discocat

Hi Alistair

We have had the wall removed between our kitchen and garage this week so it's feasible that something could have happened. However, we have looked upstairs under the floors and there is no leak. I have a horrible suspicion that it must be leaking under our concrete floors downstairs but so far we have been unable to find a heating engineer/plumber willing to undertake the job of excavating the floor!

EliteHeat

That is not a leak - it's a torrent!

The first step should be to definitively identify which section of pipework the leak is in. This usually menas cutting into the pipework and istalling isolating valves, but sometimes this is not possible - it depends on the layout of the pipework.

If it is in the concrete screed, most householders would opt to have new surface pipework installed.

The cost of digging up the screed will be horrendous if done by a contractor, if you do it then it's free.

Discocat

4 Engineers now and no-one can find the leak. It is definitely not upstairs so it must be going into the concrete floor. Neither the Plumbers nor the heating engineers can help me find the leak and I am in no position to take up concrete floors myself. I am at a total loss.... What kind of contractors would I need to employ?

SplanK

would it not be more cost effective to lay a new pipe somewhere else instead of pulling up the floor??? only downside is its a gamble incase the leak is not there!!!

adaze

I know it sounds obvious, but are you sure you have been adding water to the system? There isn't a blockage on the water main? I guess the engineers would have noticed that straight away though! Can you hear anything that might help you guess where the water is going, if you can't hear it then I guess you could eliminate those areas. If the leak was in the pipe in the concrete floor surely the fact that the concrete was formed around the pipe would mean the leak would be slow, almost airtight in fact?? Unless its actually under the whole floor and is no leaking into the ground. There are no drain cocks open or leaks under radiators?

robv_3

could be a hole in heat exchanger, pressure relieve valve leaking and not just a leaky pipe.

Speak to the insurance company and see if they cover trace and access, if so leave it to them.

sparkiedave

Can also be a deflated expansion vessel, there should be a copper pipe coming through the outside wall which then points back at the wall, is there water around that?, if so it's the pressure relief valve, if you can see where the condensate pipe runs to, is that running, you should get a small amount of liquid from it but if it's constantly running then it could be a hole in the heat exchanger as mentioned

Canucklehead

We called an emergency heating engineer out who said that it wasn't the boiler as when the pressure was high enough it fired up. He couldn't find any leaks and as he was charging £150 an hour(!) we sent him home.

We had another engineer come out today who again tried putting water in the system. He confirmed that there was no leakage from the boiler pipe outside but he had no idea where the water was going

sparkiedave


Can also be a deflated expansion vessel, there should be a copper pipe coming through the outside wall which then points back at the wall, is there water around that?, if so it's the pressure relief valve, if you can see where the condensate pipe runs to, is that running, you should get a small amount of liquid from it but if it's constantly running then it could be a hole in the heat exchanger as mentioned

Like EliteHeat I would be looking under the screed not the boiler.(Based on the op's information.)

Corgi Guy

tonysab

Do you have an update on this as we have a similar problem?

Thanks.