leak under concrete floor

[gblades]

I have a leak in my central heating system. The pressure would drop from 1.1 down to 0.3 overnight.
I have fitted a isolators in the pipework under the kitchen unit and by elimination have found that the lead is in the pipe feeding the front room radiator (not the return). There is no wet patch on the carpet so it cant be the radiator.

The floors are concrete and the front room is carpeted and the kitchen laminate. I am not too bothered about this flooring as I want to redecorate and fit new carpet and laminate anyway.

I was thinking of doing the following :-

1) Use a pipe detector to see roughtly where the pipe runs under the floor and use a nail or something to see if any joins were put inside a box section.

2) If not then cut the carpet along the path of the pipe and see if there is any discoloration and then dig up that part of the concrete.

3) If all this fails then replace the pipe.


For option (3) above I was thinking of buying a wall chaser and using that to cut a channel in the concrete. I am assuming they would be suitable as they must be designed to work with brickwork?

Then as far as the pipe is concerned I was thinking about using 10mm plastic pipe and running that inside some 15mm plastic pipe which is put in the concrete channel and then covered over. Total length of pipe required is about 7m.

Does that sound reasonable?
I could use something other than the 15mm pipe but ideally it would be something which would easily sit in the channel cut out by the wall chaser.

Thanks

 

[Newcastle88]

how much of your system is under concrete?

It's never advisable to run copper under concrete as it rots and pressurising it will find all the little pin holes.

Best advice it to repipe any under concrete pipework. 10mm plastic will work but i have always been a 22mm copper circs man and 15mm to the rads.

Leak sealer won't work as there is no oxgen for it to react to under there incase you decide to go down that avenue

 

[dextrous]

Not keen on microbore myself - 15mm would be preferential.

Rest of you plan regarding chasing it out is fine, and (depending on depth) use foam insulation to protect it prior to re-screeding the trench. Obviously no inaccessable joints within this screed should exist, which if you're using a roll of plastic shouldn't be an issue until you get to directly below the rad.

 

[gblades]

The 22mm pipework which runs round the kitchen to upstairs is in a wooden box section.
The 10mm to the downstairs rads is encased in about a 1.5mm thick blue plastic sleve. The pipework must have come with this covering as it is on tight.

The house is about 20 years old so I am guessing either movement of the pipe as it heats has worn away part of it, there is a join and this hasnt been covered properly, or movement has worked a solder joint loose (had this a few years ago in the same pipe as it joins a manifold under the kitchen cupboard).

Do you know where I can buy plastic pipe in say a 10m continuous length. I did a quick search but only saw a 100m coil.

 

[dextrous]

Do you know where I can buy plastic pipe in say a 10m continuous length. I did a quick search but only saw a 100m coil.

15mm is easily available in shorter rolls - 25m for about £25

 

[gblades]

The rest of the system is 10mm microbore and being a downstairs rad (boiler is in the kitchen) it has the output valve turned down to restrict the water flow in order the balance the system. Therefore I was thinking a bigger pipe would not have any real benefit.
I believe the plastic pipe may have a smaller bore and with inserts it will be even less. Even so given I normally have to restrict the water flow on the rad it should be fine. Sound reasonable?

I am not against using bigger pipe but I just want it to fit in the channel I can easily cut using a wall chaser.

 

[Axel]

Perhaps consider any possible alternative route for the pipes to get to the radiator instead of inside a concrete floor - cut off the old route and run up wall, through ceiling and inside upstairs floor, for example? Could be a lot less work. A boxed in section here and there can look quite discreet if done well, and is better in the long run.

 

[gblades]

Screwfix sell the 10mm pipe and also 15mm conduit pipe for it to go inside in 25m lengths which should be ok.

Now trying to figure out how to connect the pipe to the existing copper and the radiator. Looks like you can use it will compression fittings but only some types are compatible. So maybe best way is to have a short piece of 10mm pipe on the rad and then use compatible compression fitting to switch it to the plastic pipe. Then the same for the pipework under the sink.
I believe when using compression fittings you use a different type of 10mm insert than you would do if you were to use speedfit. I couldnt find these listed in the screwfix catalogue. Can you use the normal 10mm copper pipe inserts?

I thought about using an alternate run instead of in the floor but the difficulty would be bringing back down again into the kitchen as there is no free wall space. Also that would make it the furthest, biggest and the radiator with the narrowest pipework so not really a good option with balancing.

 

[kevplumb]

any compression should be ok

and the inserts should be

just a thought while you have it drained and in bits stick a new pair of rad valves on

if as you say it joins a manifold i would leave the manifold alone just cut the pipe and join on to it

 

[Gasguru]

If your house insurance covers "trace and access", there are several companies that will find the leak for you using thermal imaging and hydrogen/helium gas sniffers.

 

[stardanny]

I would cut pipes from floor and leave it, run it in 15mm from ceiling to radiators and run in first floor void, connect to 22mm pipes in wooden casing. Perfect for long term.

If you still want to go for floor, use a trunking designed for screed floor, with lid, that way you can repair pipe if it leak, without chipping away screed floor.

Dan.

 

[WDIK]

not my idea but Im told it works, put nasty cheap perfume in the system, and follow your nose

 

[Axel]

not my idea but Im told it works, put nasty cheap perfume in the system, and follow your nose

Even better - use the wife's expensive stuff - then you won't need to worry about the heating when you're staying in a hostel...

 

[gblades]

Thanks gasguru. I checked my house insurance and I am covered for tracing leaks in the central heating system so I have someone coming out to take a look and then decide on the next step to take.