Slow central heating leak

Strummer22

Hi, 

My central heating (heated by heat pump, not boiler) loses pressure of 0.5-0.8 bar per day. I can't see any visual evidence of a leak but it must be there somewhere, hidden in the solid floors on the ground floor perhaps.

I called a leak detection company who said the leak is too slow for them to be able to find it - if the system goes to zero pressure in less than a day, they would have more chance of success as it indicates a bigger leak. However,I can't leave it to see how long it takes for the to get to zero as I've got two young children and the house will get too cold. I'm topping it up once or twice a day to make sure the heating continues to function.

Anyone had a similar experience and know the best approach to fixing it, apart from waiting for it to get so bad that the leak can be located? 

stuart45

It's quite common to find a leak in a concrete floor. The problem is that if the pipes are unprotected copper there could be more than one, or more in the future. If you take up the carpet near the rads and likely pipe runs, you might see the damp patches in the screed. 

FreeBear

You say solid floors - Can we assume concrete ?

If that is the case, lift any carpet or lino and look for damp patches.

A word of warning - If you have copper pipes running through concrete, if you just repair one spot, another leak is likely to spring up elsewhere. A more permanent solution would be to replumb the system on the ground floor and keep the pipes above floor level.

tacpot12

Were the leak detection company proposing to use a Thermal Camera? If not, perhaps look for a firm that can such a camera and will come out to try to see if there is a warm spot where the water is leaking out. 

You will need to run the heating system while this is done, and at a high temperature, e.g. 70C. You will also need to lift all the carpets where the pipe run. The thermal camera can help to see where the pipes are, but you won't see the leaks with the carpets down (they act as thermal insulation). A carpet fitter will be able to refit them for you for not much money.  

As has been stated, if the pipes have been set into concrete and not protected from it, the problem will get worse, and you might start to have leaks in other areas. Although it's a big job, it's not that big. It will be messy though, so any contract to fix the problem needs to consider how to protect your belongings and who will move furniture out of the way. 

FedupBrit

My father was a plumber (not a toolmaker) but a plumber. And he fitted isolating valves on the upstairs and downstairs pipes, you could still get full bore (full diameter) fittings then.

Might be an idea to isolate the ground floor and upstairs to at least narrow it down to which floor. Or go stright to looking for the leak. Even if the pipes are set into the concrete, they should have run a channel into it. Try to work out first where the bends might be and lift the carpet/flooring there, then work your way back to the straight runs.

Concrete absorbs moisture pretty well so as others have stated you sill seen the damp. Good luck.

Strummer22

tacpot12 said:

You will need to run the heating system while this is done, and at a high temperature, e.g. 70C. 

Thanks for advice so far. Unfortunately can't run it that hot, the heat pump might get it to 55C but I can't completely override the weather compensation curve so realistically 50C might be the max achievable. 

stuart45

How old is the property?

Albermarle

stuart45 said:

It's quite common to find a leak in a concrete floor. The problem is that if the pipes are unprotected copper there could be more than one, or more in the future. If you take up the carpet near the rads and likely pipe runs, you might see the damp patches in the screed. 

Also Freebear said
A word of warning - If you have copper pipes running through concrete, if you just repair one spot, another leak is likely to spring up elsewhere. A more permanent solution would be to replumb the system on the ground floor and keep the pipes above floor level.

Out of interest what causes this? Presumably chemicals in the concrete attack the copper over a period of time ?

Kiran

Expansion and contraction due to heating and cooling causes abrasions on the pipe. Old copper pipes would have held up a bit better but they pipe wall thickness is now thinner. When we used to run pipes through concrete we had to wrap them in Denso tape before plastic pipes became a popular material 

Strummer22

stuart45 said:

How old is the property?

It's about 1860. I'm actually not sure what the ground floor is made of, I'd better pull up a corner of carpet and have a look. 

FreeBear

Albermarle said:

stuart45 said:

It's quite common to find a leak in a concrete floor. The problem is that if the pipes are unprotected copper there could be more than one, or more in the future. If you take up the carpet near the rads and likely pipe runs, you might see the damp patches in the screed. 

Also Freebear said
A word of warning - If you have copper pipes running through concrete, if you just repair one spot, another leak is likely to spring up elsewhere. A more permanent solution would be to replumb the system on the ground floor and keep the pipes above floor level.

Out of interest what causes this? Presumably chemicals in the concrete attack the copper over a period of time ?

Yes. Cement attacks the copper and causes pinhole leaks. This can be minimised by wrapping the pipes in tape as long as the tape is nonporous and has plenty of overlap.

Have also seen pinhole leaks form where plumber's flux hasn't been cleaned off properly.