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Possible leak under concrete floor

I have noticed a damp patch on concrete floor where hot and cold pipes are layed underneath. Fisrt fix central heating has been installed and coupled onto these existing pipes. Could this be a leak in old pipes maybe?

5 Answers from MyBuilder Plumbers

Best Answer

could be a leak on joint between old and new ,could be a leak on old pipe,could be a leak on new pipe, was it pressure tested before concrete/screed was laid ?,if not why not,you will have to dig it up to find out.


Answered 11th May 2019

Could well be a leak. Is the pipe copper if so has it been wrapped with a protective cover before being concreted over. As above could be old pipe could be new or joint where connected. Concrete is very corrosive to copper pipe and makes it porous over time so should be protected.

Also the pipe work should of been pressure tested both before and during the concrete being laid.

The only way your going to sort is by digging up the floor again and repairing ad necessary.


Answered 13th May 2019

Any pipework that is being burried in concrete or screed has to be either air tested or water tested to at least 4bar pressure for at least 20 minuets to test for any posible leaks. Once you are satisfied there are no leaks the pipes have to be protected to stop corrosion. If you cant pressure test the pipes you need to at least get the pipework finnished and connected to test for leaks, and ideally witnessed by the customer.If you dont do this and you are left with a damp patch you will never know if it is a pipe leaking or the damp proof damaged. You will have to lift the floor up to find out. If you can get access to the pipes before they go into the concrete you might be able to pressure test the pipework first before you lift the floor up.


Answered 5th Jun 2019

Depending on how old your cement floor is and consequently how long ago the pipes were laid beneath it your problem could be caused by the copper pipes reacting with the cement and forming small holes. It’s not appropriate to lay unprotected copper in direct contact with cement based floors. This was a practice used extensively in the 1970s and 1980s leading to leaks in solid floors particularly when putting high pressure central heating or water supplies through old pipes. If you must lay pipes beneath the solid floor either protect them with suitable materials or lay the in ducts so that they can accessed.

There are other reasons for leakage covered by other answers but in a cement floor it’s a nightmare doing a repair without causing more damage to the rest of the surrounding pipe.


Answered 10th Jun 2019

if you have combi boiler in place are you loosing pressure , I personally would dig up, see what’s going on , needs to be rectified


Answered 10th Jun 2019

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