Pressure tests for hydronic lines

Ken_7

The 2000 Uniform Mechanical Code (Section 1207.0 Testing) requires a "hydostatic" test of 100 psi for 30 minutes for flexible plastic piping (PEX) used in a radiant panel system embedded in a slab.
The Code specifically indicates a hydrostatic test.
In certain local jurisdictions, the AHJ allows an air test of 100 psi. I realize that the AHJ can allow alternate methods and practices, but that is not the question.
Is it in complinace with the Code to allow an air test?
Is the acceptance of an air test a commonly accepted practice? Do you guys see this in the field as an alternate?
Why would the Code be so specific in requiring a hydrostatic test?
Is there anything about a hydrostatic test that is inherently better than an air test?
I would appreciate your input and guidance.

Doug Wagoner

During freezing weather an air test is acceptable by inspectors in this area. Other times a hydrostatic test is desirable. The contents can be seen and the pressure drop is almost instantanious compared to air.

Tony Conner

Hydrostatic Tests...

... are much safer than pneumatic. A failure with the tubing full of water under pressure will just leak harmlessly. Something that fails with 100 PSIG of air in it is bad news. The energy involved in compressing air is considerable, and it can all be released very suddenly if something lets go.

High pressure piping that falls under ASME are usually hydro-tested to 1.5 times the safety valve setting. If air is to be used, then it's 1.1 times the safety valve setting. And if using air, you take the pressure up in increments. Go to 15 PSIG, let it sit there for a bit. If no leaks, then go up some more, and let it sit there again, and so on, until you hit the test pressure.

Any time you can use water for a test, rather than compressed air, do it.

hot_rod

I agree

water pressure is safer. Often times at the slab phase of a job neither water or power is available. If you fill with hauled water and do have a leak, it's hard to get the water back in the barrel for a second try Water is nice for radiant tube for a little extra weight also.

A hand air pump, or portable air tank make an air test very doable, in the field.

You certainly don't want a water test if there is any chance of the tube seeing freezing temperatures!

I think most inspectors understand the workability of the test medium used. In thirty plus years I have never had one insist on a hydrostatic when conditions prohibited it. The bottom line, from the inspectors prospective, is does it leak?

hot rod

Tony Conner

Ridgid...

...and Rothenberger (and likely others) make hydrostatic test pumps that are hand operated. I think Ridgid's goes to 725 PSIG, and Rothenberger's to 800. Once you have the system full of water, and the air vented, it doesn't take many pumps to walk the pressure up.

Dale

Gas services

Most nat gas services are 1/2" CTS PE plastic, a cheaper version of pex, and all are air tested for 10 minutes to 1.5 working which is 100 PSI in our area. Alll plastic main is air tested to the same pressure but a longer time, HR is correct about the risk, the gas pipe is buried to keep it safter. Steel can be tested with CO 2 or N but the hydro is much safer, getting harder to let the test water drain into the nearest creek or ditch. A regular grease gun will give over 1000 PSI use a nipple to catch the grease as not much is needed for a full tank or pipe.

Drew_2

Question? Have you ever done a hydroststic test with water and then find that the system leaks after injecting antifreeze into the system?

hot_rod

Very common, Drew

As you know glycol is "wetter" than plain water. It seems to find a way to sneak out of threaded joints. Usually after it has been heated up and thinned out.

Need to take extra care with sealing threaded joints in glycoled systems. Makes an oily, ugly mess on the fittings when it leaks, also

hot rod

Pete Novak

testing single pipe steam

I have 40 feet of single pipe steam to plumb in under a slab. It will be connected to the rest of the system, so pressure testing it to any pressure will be a problem because I'll be subjecting the entire system to that pressure. I was just going to plumb it in, turn on the boiler, raise the pressure regulator to about 6 psi and check for leaks. I think the normal operating pressure is in the range of 2psi. Therefore if it doesn't leak at 6psi, it won't leak at 2 psi. I haven't done any of this yet, but it was the easiest way I thought of so far. There might be a smarter way to do it.

Mike T., Swampeast MO

Another goofball idea...

...with glycol being "wetter" than water could you add some liquid soap to the lines when water testing? Soap does the same thing and might make those leaks show during testing.

Dan Peel

Hydrotest caution

What seems to be innocent water pressures (40-50lb) at cold fill from the well can become extreme, guage blowing, pressures when exposed pre-pour tubing is left out in the sunshine. Dan

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