Underfloor heating leak

[Rich82]

Hi there,

I'm hoping for some advice.

I had underfloor heating installed back in May for a garage conversion. Up until about a month ago, I'd not really used it as the room was warm enough. When I turned it on and set a program, I started to notice lumps in my laminate flooring. When I pulled all the floor up the entire underlay and screed floor was wet.

There are two theories as to how this may have been caused. 1, the screed had not dried completely before the laminate was laid and 2, there is a leak in the underfloor heating.

Since then, the floor has dried out. I have had the heating on which seems to work fine, as in it warms the floor up. But...

I have been advised by the company who did the underfloor heating to isolate the system. Since I did this last week, the pressure has dropped from 2 bar to just below 1 bar. This is according to the gauge that is on the underfloor heating pump, not the one upstairs in the airing cupboard.

The plumber that did the job said that it is 100% not a leak and that the drop of pressure is due to the screed around it that had not dried. Now I am far from an expert but I'm struggling to see the logic that pressure could have dropped by 1 bar in a closed system without there being a leak.

I'd be very grateful if other plumbers could give their thoughts on this. I hope I'm not being fobbed off by a plumber that doesn't want to foot the bill for the repair of my floor. Has anyone else had experience of this?

Many thanks.
Richard

 

[ShaunCorbs]

Was the floor warm when you looked at the pressure gauge?

 

[Rich82]

Was the floor warm when you looked at the pressure gauge?

No. The underfloor heating has been off for over a week now while we've been monitoring the pressure. Although I don't know how long heat is retained within screed. From memory I turned the heating off on a Sunday and then we isolated the system the following Tuesday with pressure at 2 bar. Then by Thursday it had dropped to 1.5 bar and then 1 bar by the weekend.

 

[ShaunCorbs]

I would see if it drops further eg throughout this week etc

 

[justlead1]

With the concern you describe looking for the damp spot is the first thing to find, this will confirm your thoughts. However pressure gauges do read the pressure at any particular time. But do not take in to account temperature, or whether there is air present. Which can effect pressure readings. Temperature /pressure applied to the model make very complex calculations. Expansion and contraction are a constants part of the plumbing /heating game.
Finding the damp spot is far more satisfying, which gives the confidence to dig deeper at a practical level should you need to.

 

[Rich82]

With the concern you describe looking for the damp spot is the first thing to find, this will confirm your thoughts. However pressure gauges do read the pressure at any particular time. But do not take in to account temperature, or whether there is air present. Which can effect pressure readings. Temperature /pressure applied to the model make very complex calculations. Expansion and contraction are a constants part of the plumbing /heating game.
Finding the damp spot is far more satisfying, which gives the confidence to dig deeper at a practical level should you need to.

Hi, thanks for your response.
There are no damp patches and haven't been since I removed the flooring and the screed visibly dried out within 24 hours. There has been a relatively big temperature drop in the room of approximately 10 degrees since we've had the underfloor heating turned off and the outside temperature has dropped within the last few weeks with a few mornings of frost.

If there was a leak would you expect this to rise through the screed and be clearly visible in the room? Or is there a chance it could be leaking but be contained underneath the surface?

 

[oz-plumber]

Easiest way to check for leaks now that the floor has dried up, turn the heating back on an see if there are any signs of water coming through the screed.

If signs of water then proceed with isolation of the UFH from the system and pump it up to a suitable pressure that won't damage the pipes and keep it under test for 24 or more hours.

 

[Rich82]

Easiest way to check for leaks now that the floor has dried up, turn the heating back on an see if there are any signs of water coming through the screed.

If signs of water then proceed with isolation of the UFH from the system and pump it up to a suitable pressure that won't damage the pipes and keep it under test for 24 or more hours.

We already did those tests in the beginning. After I removed the laminate floor we had the UFH on for a couple of hours a day for the best part of a week. During this point the pressure never dropped. There has been no water visible since.

The pressure has only dropped since the UFH has been isolated and turned off since last Tuesday (24/10/17). The floor and room have obviously cooled down a lot since then from approximately 21 degrees down to 14. For what it's worth, when the system was running, it did sound like there was a lot of air in it.

 

[Chuck]

The pressure has only dropped since the UFH has been isolated and turned off since last Tuesday (24/10/17). The floor and room have obviously cooled down a lot since then from approximately 21 degrees down to 14. For what it's worth, when the system was running, it did sound like there was a lot of air in it.

If you still suspect a leak, your safest bet at this stage would be to get a specialist 'leak finder' firm to help out. They use various techniques such as thermal imaging and ultrasound detection that can identify the location of buried leaks. They sometimes use chemical analysis and tracers to check that that water is leaking out from the pipework. These tend to be 'regional' rather than 'local' firms.

How many meters of what type of pipe does your UFH comprise?

 

[Chalked]

I don't think you have a leak.
It's just that the trapped moisture in the floor was released when the underfloor was turned on. This was then trapped by the flooring.
Turn it all on and back to normal. Cut a piece of polythene about 300mm square, place it on the floor and cover with a full tin of paint. If moisture is still there, it will condense on he polythene.
Once there is no moisture appearing , fit your floor.
Ps. As a precaution, monitor the heating pressure.

 

[king of pipes]

After reading all the above i am having to agree with chalked if you had a leak i would expect it to drop quicker and lower than it actually is , as a precaution i would disconnect the flow and retun pipework which connects to the UFH manifold connect it up temporarily with another test gauge and and valves fill it up off the mains then pump it up to 4 bar with a water pressure pump isolate and monitor and record the results, laminate and UFH never a good idea you need a floor that conducts heat , a 75mm screed will take 75 days to dry out unless you add a specialist chemical to the screed to speed up drying time adding flooring before then would be a mistake . cheers kop

 

[Rich82]

Thanks for all your responses. Good to know it seems like I haven't got a leak. The laminate and underlay that I used was specifically for use with underfloor heating, so there's no issue there.

I checked last night and the pressure had risen from almost zero to 1 bar. Surely that rules out a leak? The plumber who fitted it will be coming tomorrow hopefully so I'll see if I can get him to pressure test the system.