Pressure testing

[lenny]

Hi Guys

I have installed a central heating system , which I pressure tested with air. Over a period of time , the pressure has dropped. I haven't been able to find any leaks.

Is a pressure test with air as reliable as a pressure test with water ?

Cheers

Lenny

 

[tamz]

You should fill it with water then pressurise it. Not advisable to test at high pressures using air. It can be quite dangerous.

 

[Gray0689]

No if you use air it will drop eventually water is better for pre longed testing

 

[tackleburger]

No the temperature will effect it get a water pump also make sure you have no auto air vents open. If I test with air I fill to 1/2 a bar leave for 5 mins then top up and leave for say 10 mins then if it holds I increase to a bar for a a few minutes then end the dry test and test with water. I find this reliable but generally only do it if I have joints that will remain wet if there is a problem.

 

[dontknowitall]

If you pressurise with air the air can warm up and this will show a drop in pressure.

I've also found if the pressure sort of holds quite well for about 5 minutes then drops slowly it will probably be a small weep in one of the connections which you'll find when you fill it with water. 9 times out of 10 this will just mean tightening that joint a little.

 

[richw]

air is good to prove you have no open ends or made a silly mistake somewhere, wet testing is a much better method to prove soundness..

 

[diamondgas]

Because water is none compressable, unlike air, it will indicate smaller leaks far quicker and much greater pressure losses. In effect a 1bar water pressure drop over 1 min may be an un-noticable drop with air, depending on the size of the system. By far, water pressure testing gives a quicker indication as to the integrity of the system!

 

[WHPES]

Sometimes if you are very unlucky you will find when testing with cold water it will pass but as soon as you put hot water in it will spring a leak.

 

[Dannypipe]

On large systems we generally test with air (zones as we go) then the whole system.

As has been pointed out, air compresses and thus will not give as accurate results, it also means that if a fitting pings off, it will go with much more zing than if pressured with water, as you only need a small release of water to drop the pressure considerably.

Anyway it is often said you should NOT air test systems, because of the dangers described above. However it is very useful to do so to ensure you haven't missed anything obvious, which may result in water damage, and then if there is a leak, it means you don't have to drain down to repair it.

Finally it is always worth pressure testing installs with water, you should be flushing most installs anyway, so its no big deal if you have to drain to make the repair.

I have a rig that I made up for my compressor, with a guage, leverarm valve and compressor male adapter. We pressurise, lock off and monitor. We're looking for the needle to quickly drop, if it doesn't its a good indication everything is ok.

 

[diamondgas]

Too true WHPES

I once flooded downstairs after a day beacuse flux had helh back a poor joint! Inly heat revealed the problem!!

 

[Billy Bob Bob]

Too true WHPES

I once flooded downstairs after a day beacuse flux had helh back a poor joint! Inly heat revealed the problem!!

yep had that happen too,its a pig

 

[GQuigley67]

testing with air I believe is better than testing with water, air can get where water can't.

 

[Dannypipe]

Read this:

All you need to know!!

http://www.ukcopperboard.co.uk/literature/pdfs/Installation-Tips/Pressure-testing-piping-systems.pdf

 

[steosman]

Dodgy solder joints will hold under a cold water test but when hot water is circulated through pipe work they will pop. It happened to me on a house, luckily house was gutted at the time. Always leave floor boards loose and any plaster board until heat has been run through pipe work. If you were in a rush to put back floor boards and the gas has not been connected yet, use immersion to heat water, fill buckets with very hot water, empty into pressure test pump and fill system. Air is not reliable but as said above will show up joints that were passed by and prevent damage. 1- air test 2- test with water 3- test with hot water if needed