Maintain pressure prior to screed

[Post and beam]

I had the UFH pipes laid today, screed on thursday.

 

So i thought i would do the sensible thing and take a picture of the pressure reading as soon as it was signed off.

 

I had occassion to check it again 6 hours later and was very suprised and more than a little concerned to see the difference.  And yet there is zero sign of a leak anywhere of course, everything is fine.

 

I had imagined that ' make sure it maintains pressure'  meant the same pressure.  Yes , i know that temperature can make a difference and atmospherics but thats quite a percentage change in a few hours.

[Nickfromwales]

Have you closed the cap on the automatic air vent?

 

[Post and beam]

Nick i haven't touched anything

[Nickfromwales]

9 minutes ago, Post and beam said:

Nick i haven't touched anything

That's the best reply any stranger can offer to a random guy on the internet at this time of night. 

 

Is the cap on the automatic air vent open or closed? It's the thing that looks like the air cap on a car tyre. Can we have a better pic of the whole manifold?

[Post and beam]

1 minute ago, Nickfromwales said:

Can we have a better pic of the whole manifold?

I will check when i am on site tomorroe and take a picture. assuming i may not be able to get the installers back to site before the screeders arrive and also that there is in fact a problem. Can i resolve this myself ?

 

[Nickfromwales]

2 minutes ago, Post and beam said:

I will check when i am on site tomorroe and take a picture. assuming i may not be able to get the installers back to site before the screeders arrive and also that there is in fact a problem. Can i resolve this myself ?

 

Let's be sure there's an actual problem first   The biggest "oops" here will be a wet test done and then somebody simply forgot to pinch off the cap on the AAV. The air in the loops then rises to the manifold rail and ejects itself, resulting in a drop in pressure.

 

If you had a significant leak there would be zero pressure on the gauge right now. 

 

 

[Post and beam]

Or tomorrow even

[Nickfromwales]

Just now, Post and beam said:

Or tomorrow even

We shall put that typo down to nerves  

[Post and beam]

I was going with stupidity to be honest

[Nickfromwales]

Just now, Post and beam said:

I was going with stupidity to be honest

Nobody will ever know  Let's keep it between you and I.

[Conor]

If you've no expansion vessel, the slightest change in temperature or air escaping can make a huge difference to the pressure. Don't worry about it.

[Bonner]

I agree, nothing to worry about here. Most likely a slight weep in a joint (if anything) and there shouldn’t be any joints in the screed! You might find the pressure shoots up after the screed is poured due to chemical reaction.

[Post and beam]

59 minutes ago, Conor said:

If you've no expansion vessel

Not got this far yet. Only have the manifold and pipework. I am concerned that if the pressure falls further, or is considered too low now for whatever reason then can i still get the screed pour tomorrow. If not i need to call them off this morning.

[Nickfromwales]

Has it been wet or dry tested?
 

Have the loops been purged through, eg so all the air got blasted out?

 

You’ve not answered about the cap on the bottle vent. 

[G and J]

I once checked a section of pipe work that was about to be boxed in - it didn’t hold pressure.  
 

Worked the issue and eventually, after replacing half of it, discovered that my pressure tester was leaking, the pipe work was fine.   Might be worth checking that the tester is working fine.

[Nickfromwales]

1 hour ago, Bonner said:

You might find the pressure shoots up after the screed is poured due to chemical reaction

Yup. Ideally you should be opening a pipe to atmosphere immediately prior to the screed going down, as when you’ve got a gauge installed it will usually meet its maker when the pressure exceeds its max set point and the needle snaps off. 
 

If you need it all pressurised for the pour then you can just accept the cost of a replacement gauge if that happens, a tenner or two at most.

[Nickfromwales]

1 minute ago, G and J said:

I once checked a section of pipe work that was about to be boxed in - it didn’t hold pressure.  
 

Worked the issue and eventually, after replacing half of it, discovered that my pressure tester was leaking, the pipe work was fine.   Might be worth checking that the tester is working fine.

The tester is the manifold gauge   

[G and J]

6 minutes ago, Nickfromwales said:

Yup. Ideally you should be opening a pipe to atmosphere immediately prior to the screed going down, as when you’ve got a gauge installed it will usually meet its maker when the pressure exceeds its max set point and the needle snaps off. 
 

If you need it all pressurised for the pour then you can just accept the cost of a replacement gauge if that happens, a tenner or two at most.

I had assumed that keeping the pipes pressurised during the poor reduces the probability of ‘treading on’ damage.  Are the UFH pipes tough enough without?

[G and J]

7 minutes ago, Nickfromwales said:

The tester is the manifold gauge   

Well in all my years I’ve never fitted an UFH manifold with a pressure gauge on it!

 

(That is, I’ve never fitted UFH…. every day is a school day.  Shame about all the detentions lol)

[crispy_wafer]

keep them pressurised, but when it's walkable, just release some pressure as the heat from curing will cause what nick says.

[crispy_wafer]

3 minutes ago, G and J said:

Are the UFH pipes tough enough without?

 

yes, plenty tough!  You'll do well to damage them to be honest

[G and J]

6 minutes ago, crispy_wafer said:

keep them pressurised, but when it's walkable, just release some pressure as the heat from curing will cause what nick says.

So it’s a good idea to maintain access to the manifold during the pour?

 

6 minutes ago, crispy_wafer said:

 

yes, plenty tough!  You'll do well to damage them to be honest

Good to know.

[Nickfromwales]

7 minutes ago, G and J said:

I had assumed that keeping the pipes pressurised during the poor reduces the probability of ‘treading on’ damage.  Are the UFH pipes tough enough without?

I hardly ever pressure test tbh. The pipes (pert al pert) are pretty bombproof and you have to maliciously damage them to get one to leak.

 

Been fitting UFH for a quarter century or more, never had an issue with getting pipe out of a box, on to a floor, and covered in the good stuff. MBC never bother either, iirc. It’s just bloody solid stuff and has an extraordinarily low failure rate (which is why it’s good to bury in the floor for the next 30+ years or more). 

[Nickfromwales]

10 minutes ago, G and J said:

Well in all my years I’ve never fitted an UFH manifold with a pressure gauge on it!

Me neither, I always take out the pressure gauge and fit a second bottle vent in the hole.

 

2 minutes ago, G and J said:

So it’s a good idea to maintain access to the manifold during the pour?

Or extend a bit of push fit plastic pipe from the manifold to where you can access it without going full on Billy Elliot, with the gauge on the end of that, and a 1/4 turn tap to bleed off the rising pressure as the concrete cures.

[crispy_wafer]

Just now, G and J said:

So it’s a good idea to maintain access to the manifold during the pour?

 

Mine was accessible, but then I was in with the screeders with my wellies on taking pictures and videos of the pour slopping around in it.  It was only after a few hours when I went to have a look at my screed did I clock that the temperature had risen and I ought to check the ufh to double check we hadnt done any damage noticed the gauge was now at a higher bar number than I'd left it, so I cracked it a touch to relieve some pressure from the system.