UFH test pressure and duration.

[Alexphd1]

Few... I was starting to think I bought a lemon.

 

[Russdl]

Help!

 

Our MBC slab with UFH arrives tomorrow. Whilst I don't know the exact timescale I suspect there won't be many days (if any) between the UFH pipe being laid and the screed covering it.

 

I'd forgotten that MBC don't do a pressure test of the UFH pipes, and I've just reminded myself!

 

Do I need to do a pressure test before the screed covers the UFH pipes, there seems to be a mix of views here? 

 

 

[Jeremy Harris]

I didn't bother, mainly because when I looked at the pipe and the way it was laid and tied to the steel fabric it seemed pretty clear that there was no easy way to damage it.  You will probably have an evening when the pipe's tied in before the concrete pour the next day.  Ask the chaps when they get on site what their schedule is, as they usually like to get the concrete pour done in the morning, so they can let it go off enough to start to power float it before it gets too late in the day.

 

Do you know who from MBC is doing your slab?  If it's any of the guys that did ours I might pop over and say hello.

[Onoff]

28 minutes ago, Russdl said:

Help!

 

Our MBC slab with UFH arrives tomorrow. Whilst I don't know the exact timescale I suspect there won't be many days (if any) between the UFH pipe being laid and the screed covering it.

 

I'd forgotten that MBC don't do a pressure test of the UFH pipes, and I've just reminded myself!

 

Do I need to do a pressure test before the screed covers the UFH pipes, there seems to be a mix of views here? 

 

 

 

I think the pressure test before screeding is a must.

 

What varies is whether people leave it under pressure whilst the screed goes off. I did and saw a slight increase in pressure as the wet concrete (in my case) cured. There is a school of thought that pressurizing the pipe expands it slightly as would happen when it's running. Tbh with mesh in the slab does it matter?

[Jeremy Harris]

If I had to guess, I'd say that any pressure rise seen during curing was entirely caused by the concrete warming up, as the curing reaction is exothermic.

[Onoff]

4 minutes ago, JSHarris said:

If I had to guess, I'd say that any pressure rise seen during curing was entirely caused by the concrete warming up, as the curing reaction is exothermic.

 

That's what Nick said but without the big words...

[scottishjohn]

always suprised me how much tyre pressures went up on the race car if one side was in the sun and other side in shade when sat  in the pits--could be 2psi rise on one side and 1psi drop on other

that was what made us get a nitrogen system for the garage 

basically an osmosis set -up --compressed air in --and filtered out all oxygen + water vapour from it  give near pure  nitrogen 

tyre pressures stayed constant after that ,also noticed on customers cars how pressure drop between services was virtually nil ,unless rim leaked on older cars -tyres lasted longer as well ,or so customers reported-,maybe just because they were always at correct pressure .

 

[Russdl]

28 minutes ago, JSHarris said:

Do you know who from MBC is doing your slab?

 

Harry is the only name I have so far, I'll let you know when I meet them tomorrow.

~~~~~

 

1 hour ago, Russdl said:

there seems to be a mix of views here? 

 

30 minutes ago, JSHarris said:

I didn't bother,

 

29 minutes ago, Onoff said:

I think the pressure test before screeding is a must.

 

Doh! There you go, two Guru's with polar opposite views. 

[newhome]

2 hours ago, Russdl said:

Doh! There you go, two Guru's with polar opposite views. 

 

No guru, but we did the pressure test before screeding. 

 

[Onoff]

I'm no guru, more monkey see, monkey ask / copy!

 

If it helps @Nickfromwales tells tales of labourers humping barrows full of screed etc over Pex-Al-Pex and denying it without detriment. 

 

I'd just worry about a manufacturer's defect.

 

If you have the test kit I can't see the issue. Tbh I tested mine off mains water with a home made rig and held it at 3bar...for months before the slab went down  I had a couple of dents and kinks but was more worried about some abrasions. My pipe is under my A142 mesh and walking on it for so long before the slab was done I managed to chaff the Pex-Al-Pex outer layer in a few places.

Edited May 1, 2019 by Onoff

[Ferdinand]

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Edited May 1, 2019 by Ferdinand

[Russdl]

46 minutes ago, Onoff said:

If it helps @Nickfromwales tells tales of labourers humping barrows full of screed etc over Pex-Al-Pex and denying it without detriment.

 

I'd read that and interpreted it as 'don't bother' though he doesn't use those words.

 

46 minutes ago, Onoff said:

If you have the test kit I can't see the issue.

 

I don't.

But I was looking at buying the manifold, fitting it (dangling freely in the air, supported on some Heath Robinson timber frame) and filling all the circuits with water to about 3 bar, because 3 bar is about all I've got. Would that suffice as a test kit?

 

 

[Onoff]

32 minutes ago, Russdl said:

 

I'd read that and interpreted it as 'don't bother' though he doesn't use those words.

 

 

I don't.

But I was looking at buying the manifold, fitting it (dangling freely in the air, supported on some Heath Robinson timber frame) and filling all the circuits with water to about 3 bar, because 3 bar is about all I've got. Would that suffice as a test kit?

 

 

 

That's what the Welsh Wizard told me to do. @Nickfromwales ?

[TerryE]

We didn't and didn't have any problems.  The MBC crew that we used said that they'd never had any problems with any of their slabs.  We use an up-and-over pumping system for pour so we didn't have any material issues with heavy barrows over the pipe runs.  So IMO, the risks are low and if at all they are during the pour itself.  There are two other factors that you need to consider:  

• We were getting our slab laid in early Nov, so there was a real risk of the slab going below 0°C with water in the pipework. Really not a good idea, so you should really blow out the water after the test. 
• Doing the pressure test involves fitting the manifold (and possibly needing to reposition and refit it when you have the TF adjacent wall in place), as well as the test itself.  This is going to man that the MBC crew is going to have to schedule a gap day between completing the UFH (typically the last thing that they do before the pour) and doing the pour itself.

I did do a pressure test (IIRC, about 6 months later in the early spring) and cranked the loops up to 5 bar with no problems.  We run the UFH at 1bar now. 

[Nickfromwales]

5 hours ago, Onoff said:

 

That's what the Welsh Wizard told me to do. @Nickfromwales ?

MBC don’t bother, just whack the pipe in and away to go. There’s too much going on on a new build to risk fitting delicate things like manifolds ( flow gauges are very easy to damage ) so I only ever do that now if there’s a pipe been damaged & repaired and it needs proving. 

Tbh you can just do that with a temp rig anyhoo, so as long as there’s no excessive foot traffic / narrowing then I would say don’t worry. 

Thats re Pex-Al-Pex with the aluminium liner. It’s tougher than Charles Bronson and Jean-Claude Van Damme’s love child. ?  

[Russdl]

1 hour ago, Nickfromwales said:

Tbh you can just do that with a temp rig anyhoo, so as long as there’s no excessive foot traffic / narrowing then I would say don’t worry. 

 

Ok, thanks Nick. Harry did say that out of the numerous slabs he'd installed he knew of about 3 people who'd tested before the screed, so I'll go with the flow, not test it, and keep my fingers crossed.

 

 

[Conor]

As a general rule, pressure tests on pipelines are generally X1.5 the anticipated max operating pressure, or the max pressure rating of the system, whichever is lower. I'd expect the pressure on a domestic system to be no more than 1.5bar at the highest point and 2bar at the lowest. So test pressure of 4-5bar is adequate.

[Barnboy]

I'm just about to pressure rest my freshly laid ufh pipe, I've been searching for what pressure to run it at and the go to seems to be about 5/6 bar.

I'll be setting the pressure straight through the manifold with a garden hose and a top up of compressed air.

There won't be an expansion vessel fitted at this stage so what pressure should I leave the system under whilst the liquid screed is poured ?

I dont want to leave it too high and then it rise too high with the heat effect of the concrete curing.

[JohnMo]

If putting water in you need anti freeze, otherwise you may end up splitting pipes if they freeze.

 

The alternative is just air.

 

I used Glycol/water in mine, once pressurised, I left it like that until I connected it to my boiler.

[Barnboy]

I've had my system sitting at 6 bar for 2 days now, should I leave it at this whilst the liquid screed gets poured, or decrease the pressure a little, and if I do decrease it what pressure do I leave it at  ?

[Tosh]

46 minutes ago, Barnboy said:

I've had my system sitting at 6 bar for 2 days now, should I leave it at this whilst the liquid screed gets poured, or decrease the pressure a little, and if I do decrease it what pressure do I leave it at  ?

I don't think there's any need to leave it at 6bar, it's really just to test the joints above their normal operating pressure. I dropped ours down to 1.5 bar when they poured the screed and just monitored it. It went up to 4bar shortly after pour then dropped back down to 1.5 after a few days if I recall.

[Barnboy]

Thanks @Tosh

I'll drop it down to around the 1.5bar mark, I wasn't sure how much the heat of the curing screed would push the pressure up by and wasn't quite expecting as much as yours went up so thank you.