UnderFloor Heating Pressure Testing

[mdproctor 1]

Polypipe, JG and others state you must keep the system pressurised throughout the screed drying period.

Others, such as Florad, state that pressure only needs to be maintained until the screed is laid, and that it does not need to be mainted for screed drying period (3 to 21 days, depending on the screed).

Who is right, and why?

Mark

[Rich 2]

Hmm, polypipe is seriously tough pipe, often used for incoming mains water, the thick walled blue stuff right?

I cant imagine why it would need to be pressurised during screeding, you can drive over that stuff and it wont collapse...

Still, you loose nothing by keeping it pressurised, regardless of manufacturer..

[mdproctor 1]

Hmm, polypipe is seriously tough pipe, often used for incoming mains water, the thick walled blue stuff right?

I cant imagine why it would need to be pressurised during screeding, you can drive over that stuff and it wont collapse...

Still, you loose nothing by keeping it pressurised, regardless of manufacturer..

The plumbers answer was that the pipe is cold and will expand when heat is put through it, but keeping it pressurised you ensure expansion room.

The builders use Florad and Florad advised them that this wasn't necessary. So a bit of a "****ing contest" happened between the two parties and the plumber walked off the job. I then did my own research and saw that many companies (polypipe, jg) do recommend to keep the system pressured through during, as the plumber said.

I've since persuaded the plumber to come back onsite, the compromise being the system remains pressurised as long as he feels fit. However Florad are still adamant he is wrong, and I personally would like to get to the truth in the matter.

[Rich 2]

Thats sound weird to be honest, polypipe doesnt expend under pressure, its tempurature that makes it expand, not pressure, as the plastic only changes composition when heated, thus can expand, thats basic physics/science..

Although, given your drawings, the polypie must be really thin and flexible, so it probably does stretch under pressure, like a garden hose, sort of.

I'd go with the Plumber, pressurise it the entire time, then if it shrinks a bit when cold, there is space in the cavity for it to shrink, rather than lay the floor with it shrunk, then crack the floor as it expands and heats up...

That much is logical, no matter what pipe you lay down.

The only danger that seems obvious is if the pipe gets damaged during the screeding, your going to have a right mess everywhere if it splits or gets cut, but screeding doesnt require sharp trowels..

So you have 1 supplier saying its not necessary, so really, thats the same as "You can if you like, but you dont need to" as they are not saying "Dont", just that you dont have to if you dont want to ggo to the extra work.

[CDS 1]

I know this is an old post but just in case anyone looks at this in the future:

All underfloor heating pipework MUST be pressure tested before the screed is installed (see BS EN 1264 Part 4). This is to check that it is water tight.

From the screed point of view: There is no need to maintain the pressure in the pipe during screeding. The pipe will not expand/contract or anything else. The only discrepancy to this is if the UFH pipe is Rubber in which case it will collapse But I would not use this type of pipe.

From the Underfloor Heating Point of View: I always advice that the pressure is maintained during screeding and most if not all UFH manufactures will do the same. The reason is that if any damage occurs to the pipe and it is punctured the pressure will drop and action can be taken.

So whilst screeding maintain the pressure test and check that the pressure is holding after each area has been screeded. If the pressure drops (ignore small fluctuations) then stop screeding and investigate.