Pressure test in concrete slab tubing

[andyvh1959]

My brother put down the slab for his shop, oh... 20 years ago, up here is east central Wisconsin. The slab was poured with PEX tubing, two zones, and now he is finally building his shop. He will pressure test the two circuits before going ahead and filling the system. Pressure test the tubing with 100 psi through a valve and gauge, fed from an air comprseeor, so he can monitor the pressure over a 24 hour period. If no pressure drop the tubing should be good to go. Any other suggestions?

 

[Gutman]

Watching as others will add better info, but the thing I would add is blow down the lines to clear anything that may have accumulated in the 20 years, despite the best efforts at closure back then. I was amazed at what I've seen emerge from the nether regions of a decommissioned system.

 

[JohnX14]

I don't think you need anywhere near 100 psi to test that tubing.... What's the pressure on a boiler? 15 psi?

 

[PoorUB]

I don't think you need anywhere near 100 psi to test that tubing.... What's the pressure on a boiler? 15 psi?

I worked in HVAC and installed thousands of feet of floor tubing, all pressure tested to 100 PSI. Our local inspections required 100 PSI.

We used only water and had a high pressure hand pump to get to 100 PSI. You can use a small centrifugal pump and get to around 40 PSI. If you use nothing but water a small leak shows up right away.

 

[finn]

I recall 35-50 as being the recommended test pressure.

Been a long time, though.

 

[HoosierBuddy]

100 PSI would be a strength as well as a pressure test.

If the concrete is already poured....I'd go lower than that. If this is prior to concrete...then test could be as high as the pipe's pressure rating.

 

[PopcornSutton]

100 PSI would be a strength as well as a pressure test.

If the concrete is already poured....I'd go lower than that. If this is prior to concrete...then test could be as high as the pipe's pressure rating.

This makes sense. If new work, I would test maybe up to 100, I would leave pressure on during the concrete work but at a lower pressure, maybe 50. I would think pex could be easier to puncture if rock hard so a little give might help. And I would leave the pressure on until put in service, which would likely be maybe 15PSI?

 

[HoosierBuddy]

This makes sense. If new work, I would test maybe up to 100, I would leave pressure on during the concrete work but at a lower pressure, maybe 50. I would think pex could be easier to puncture if rock hard so a little give might help. And I would leave the pressure on until put in service, which would likely be maybe 15PSI?

My hydronic system runs at 15 PSI ish.

The makeup water is connected to city water through a regulator. I guess if I was planning for "worst case" scenario, I might consider whatever the city water pressure is as what it could see if the makeup pressure regulator failed open.

 

[andyvh1959]

All good input. His slab is 20 year old, the tubing was in place when the slab was poured. He sealed the tubing with the connection manifolds but he never built his shop until now. So the slab and tubing has been in place unused but protected for 20 years. I still think 60 psi is a minimum pressure test, at minimum 60 psi its a 4:1 working pressure test if the boiler system operates at 15psi.

 

[mm08822]

If you rupture the tubing at 60 psi, it may be in a location that can't easily be repaired.

2x operating should be sufficient. Purging first with clean water to eliminate slime and air first is a good idea. Then pressurizing the system already filled with water makes for easy leak detection.

Keep a gauge on it for at least 24 hours. Sun shining on the slab could tweak the pressure due to heat input. Should be minimal with water as compared to air only.

Blow out the water if there is still a chance of freezing until system operational.

 

[andyvh1959]

Good points, I'll do the pressure test to 30psi. Prefer to use a digital gauge as it can show degradation over time in 0.1 psi increments.

 

[Ak Jim]

Was the PEX tubing exposed to sunlight?

 

[Dagny]

very good question.

 

[Stuart in MN]

The Uponor installation manual says either air or water can be used for the pressure test, they recommend 60 psi for 24 hours. https://www.uponor.com/getmedia/417...eating-installation-handbook.pdf?sitename=USA The manual should also be useful for the procedure for filling the system and commissioning it.

 

[andyvh1959]

The tubing has never been exposed to direct sunlight since the slab was pored 20 years ago. So I'd expect no degradation at all. My brother sealed the tubes with the manifolds installed and nothing in the floor zones, no air or water, its all been covered and not exposed for 20 years. So assuming no tubing failures and nothing getting into the tubing there should be no reason to expect a fault or failure. Since the test will only prove the system has no pressure leaks just using air to charge the zones is adequate, no need to fill the system with water now and then pressurize it to test it.

Once it confirms the pressure test, we'll blow it clear and then fill it with 50/50 water glycol or whatever is recommended for in floor heating systems. He'll likely get the electric boiler from Menards.

Here is the most recent pic of his build as of today:

Two car wide on the right and 24' deep. Tall one stall on the left for his Isizu 1.5 ton dually truck, which is 11' tall. Floor to peak inside on the left is close to 18' inside. The right side will have a mezzanine above the two car storage lifts. So he'll have to insulate it well to make sure the two heat zones in the floor can keep up with all that vertical space to heat. In that respect, he may be best off to create an interior second floor unheated storage space instead of heating all that vertical space.

 

[dcg9381]

Pressure test the tubing with 100 psi through a valve and gauge, fed from an air comprseeor, so he can monitor the pressure over a 24 hour period. If no pressure drop the tubing should be good to go. Any other suggestions?

Plumbers (as far as I know) use a pressure test gauge and typically a schrader valve to "exempt" the compressor itself from being part of any leakage problem.... something like this.

Apologies if you're already aware... But testing HVAC, gas lines, water lines, I like to over-pressurize from working pressure and give it 2 days to see if it leaks.

 

[andyvh1959]

Agreed. Works like a leak down tester for an engine, which I happen to have. You charge the system with a regulated pressure, then shut off/isolate the air compressor as the source, and monitor the charge in the system. So if I test charge the system to 60 psi, from the sir compressor, then shut off the compressor as the source and use the bleed screw to get to the test pressure, Then shut off the bleed screw and monitor the pressure for at least 24 to 48 hours.

 

[racecougar]

The reasoning behind using water rather than air is that water doesn't compress and create a potential bomb like air does.

 

[mike93lx]

The tubing has never been exposed to direct sunlight since the slab was pored 20 years ago. So I'd expect no degradation at all. My brother sealed the tubes with the manifolds installed and nothing in the floor zones, no air or water, its all been covered and not exposed for 20 years. So assuming no tubing failures and nothing getting into the tubing there should be no reason to expect a fault or failure. Since the test will only prove the system has no pressure leaks just using air to charge the zones is adequate, no need to fill the system with water now and then pressurize it to test it.

Once it confirms the pressure test, we'll blow it clear and then fill it with 50/50 water glycol or whatever is recommended for in floor heating systems. He'll likely get the electric boiler from Menards.

Here is the most recent pic of his build as of today:

Two car wide on the right and 24' deep. Tall one stall on the left for his Isizu 1.5 ton dually truck, which is 11' tall. Floor to peak inside on the left is close to 18' inside. The right side will have a mezzanine above the two car storage lifts. So he'll have to insulate it well to make sure the two heat zones in the floor can keep up with all that vertical space to heat. In that respect, he may be best off to create an interior second floor unheated storage space instead of heating all that vertical space.

The manifold and tubing coming out of the slab has been protected too?

 

[CraigStu]

I would test w/ air first just because it will be easiest to do. If it leaks you are probably done. If it's a tiny leak maybe try to locate it using water?? But, would you want to cut into a slab to fix a leak? Maybe not worth it.

 

[andyvh1959]

Far as I know my brother had everything covered to protect it from any exposure, including sunlight. Yeah, if a leak is evident, well then the whole deal is done. His builder did run one anchor screw into the middle of the floor to run a support brace up the walls before getting the trusses on top. Builder claimed he didn't run into anything after drilling the hole, so a pressure test will prove that and at least locate the leak if its evident. IF a leak is there, time for the old plumber trick of pushing white bread into the tubing at the hole, seal it with JB Weld or similar, then flush the system with water to push out the bread plug, and use concrete patch in the drill hole.

 

[willymakeit]

Check your pressure at same time of day if possible. Ive seen some varations enough to cause your heart to jump

 

[andyvh1959]

The reasoning behind using water rather than air is that water doesn't compress and create a potential bomb like air does.

True. Air does compress, so limit the test pressure to 100 psi or less. If you do a test with water you'd still have to pressurize the circuit, and then blow out the water to fill the circuit with 50/50 water/glycol.

 

[PoorUB]

The reasoning behind using water rather than air is that water doesn't compress and create a potential bomb like air does.

Not a concern with floor tubing. Floor tubing doesn't explode like an 80 gallon air tank when it fails.

The biggest reason for testing floor tubing with water is a tiny leak shows up faster and is easier to find. Also, if the tubing is left with water pressure in it and a contractor happens to puncture the tube they will notice it instantly.

 

[PoorUB]

True. Air does compress, so limit the test pressure to 100 psi or less. If you do a test with water you'd still have to pressurize the circuit, and then blow out the water to fill the circuit with 50/50 water/glycol.

You leave the water in and pump the glycol mix into the pipe and wait for it to flow out the other end.
I have done a lot of floor tubing, always pressure tested with water and never blew the lines out. I was in charge of one job and the glycol mix showed up in a semi truck with a PTO driven pump. We pumped each loop, one at a time and measured the glycol as it ran out the other end with a refractometer. When it was good ratio that loop was closed and on to the next.

 

[andyvh1959]

So you filled the circuit with water, then applied 60 to 100 psi air pressure to the circuit? If the pressure maintined for 24 hours bleed off the pressure and fill the circuit with 50/50 water glycol.