Testing underfloor heating

[Milleniumaire]

As part of our new kitchen extension, the builder is installing a solid concrete floor and underfloor heating, the area being approximately 50 square meters.

Yesterday our builder laid the insulation, then underfloor heating mats and pipes. I'm not sure which brand, but it looks like a kit as the pipes are pushed into the plastic mats that are put down on top of the insulation.

I was expecting him to do some testing of the pipes by filling with water, but the pipes haven't even been connected to the manifold.

This morning the sand/cement screed started to be laid over all the pipes. My initial concerns about not testing the pipework were somewhat alleviated when I saw wheel barrows and big blokes wearing big boots stamping all over the pipework! I say this, because it seems to me that any tests that may have been done wouldn't have identified any damage caused while laying the screed!

Various websites seem to be suggesting the pipes should be pressure tested and the screed put down while water is in the pipes (so they are expanded), but none of this is happening. Of course, if there are no obvious signs of leakage when it is eventually turned on then that's great and not testing has saved a lot of time, but if it is found to be leaking, the screed will be hard and our new kitchen will have already been installed - so lots of potential upheaval.

Am I worrying unduly or should the pipework REALLY be tested before this stage and should I have words with the builder (although it's probably already too late)?

 

[gasanstuff]

I always pressure test pipework and leave pipes under pressure whilst the screed is being laid.

You may be ok but maybe not. Seems like getting a builder to do a plumbers job doesn't mean it's done correctly.

 

[Milleniumaire]

It was one of my concerns about having the builder put in the underfloor heating, however, when we were discussing it he gave the impression his plumber would be doing it. Apparently, what he meant was his plumber would be connecting up the pipes to the manifold and boiler. He has done the "hard labour" job of laying the pipes and he is using a company to lay the screed as I type.

The other reason for using the builder was that he was going to remove the existing suspended timber floor in the kitchen and replace it with a solid concrete floor, which also runs through to the new extension. As the builder is laying the floor it seemed to make sense to let him "do" the whole of the floor as then he could control when things happen i.e. it wasn't necessary to try to get a plumber in on a specific day, or wait for a plumber to be available. As a result of him doing the work it has been done very quickly, but I am concerned that it may just be too rushed without enough checks.

 

[Milleniumaire]

Assuming there are no leaks, I guess the reason for "pressurising" the pipes while laying the screed is to protect the screed from cracking when water is initially pumped into the system. The pressurised pipes would expand and make a slightly larger channel through the screed. However, when the pipes then contract, doesn't this leave an air space around the pipe (albeit a small one), which isn't ideal for the transfer of heat to the surrounding screed.

Assuming the screed is left long enough (1 month, 2 months?) to completely harden, is it really likely that the pipes would expand and crack the screed? I can understand this happening if the pipes are filled too soon and the screed hasn't fully hardened, but I imagine the screed being hard enough (almost like concrete) and preventing the pipes from expanding.

Lots of assumptions from me, but this is the first time I've had underfloor heating installed.

 

[gasanstuff]

How many pipes are coming out of the screed?

 

[Milleniumaire]

There are 3 loops, so 6 pipes into the garage where the manifold will be fitted.

 

[doitall]

are they all roughly the same length.

Yes the pipes should be flushed, tested and under pressure when the floor is laid.

Plastic pipe is easy damaged, at the very least I would insist on a 6bar water test for 24 hours, before the kitchen goes in, and make sure they don't cheat by turning the valves off once its under pressure.

How deep s the screed going to be. ??

 

[gasanstuff]

Assuming pipes are at 200 mm centre then hopefully pipes are the same length you may be ok, as long as heat loss calcs etc done and insulation up to spec.

200 mm centre equals 5m pipe per square meter..

150mm centres then you may be in a spot of bother!

 

[Milleniumaire]

I believe the pipes do have 200mm centres and the screed will be around 70mm thick according to the builder.

I'm not sure if the loops are equal lengths, but I seem to recall 60m per loop being discussed. That's 180m in total and the area (excluding kitchen units) is around 38 square metres, so that fits in with 200mm centre = 5 linear metres.

Unfortunately or fortunately, depending how you look at it, the kitchen fitters are due in on Thursday, so there's no way the underfloor heating can be tested before then!

I guess it's just a case of crossing my fingers that everything will be okay at this stage!

Here's a photo of part of the area being prepared:

View media item 77630

 

[picasso]

I cant believe anyone would be stupid enough to put ufh in without testing it, who is gonna take responability for it if it does leak ?

another question, have they put in the insulation around the perimeter ?

 

[Milleniumaire]

We are paying the builder to install it and he will employ whoever is required, so from my point of view the builder is responsible if there's a problem.

What I'm not sure about is how long it will take before we know there is a leak.

I'm already considering waiting a couple of months before putting down floor tiles to ensure the screed has fully hardened and to enable us to fully test the heating.

 

[Milleniumaire]

Out of interest, is it normal to find leaks in the pipes when they are laid or is this a very rare occurrence?

 

[Milleniumaire]

Hi picasso, sorry I've just noticed your question. The answer is yes they did put insulation around the edges of the room.

The photo is showing the pipes partially laid (there's more space behind me). By the time they had finished and everything was ready for the screed, there was insulation in place. It was flimsy looking, as though it came off a roll and nothing like the big thick pads of insulation put on top of the concrete floor.

 

[St0rmer66]

I wouldn't even 'not' test over-floor pipework if it was going to be concealed, let alone underfloor pipework! . Builder will be responsible if it leaks so it's on his head. You might be lucky.

 

[ALCPlumbing]

At least with underfloor heating there is no joins in the pipe. It is one entire length. This means there is a lot less chance of there being a leak but it's not unheard of. Any serious plumber who cares about his reputation tests their pipework.

Good luck. I'm sure you'll be fine but I'd be crossing my fingers and anything else you can cross when they fill it up.