About 40 years ago my Dad pressure tested a DIY plumbing installatio
using a car tyre valve (soldered somehow into a 1/2 inch BS compression fitting), a foot pump and a car engine compression gauge. After filling the system with compressed air he left it overnight an checked for pressure drop. Does anyone know if this would be an appropriate way to test a plasti (JG Speedfit) central heating system prior to filling (the gas fitte is coming to fit the boiler on Tuesday)? I can seal off the open ends
Yes. You can buy an adaptor with a 15mm pushfit, a tyre valve, and a pressure guage, e.g.
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's much easier to dry test in sections than it will be to do the whole system at once, but if you've already constructed it all, I wouldn't bother breaking it apart now. It takes a lot of effort to pump up even a couple of radiators to 2 bar, and I wouldn't dare go that high with a whole system, as the energy stored in it will be massive -- if any part does break apart it will fly apart explosively (release the pressure gradually when you're done, from something like a bleed valve, not by pulling apart a fitting;-). The relevant British Standard recommends evacuation of the building when pressure testing pipework with air.
I would suggest getting a can of gas leak detector spray too. You spray this on all the joints and it will give a much faster and more accurate indication of any leaks than will watching for a drop on the pressure guage (grows a large gobit of cuckoo spit at each leak site). I can't see this in screwfix's online catalogue, but any plumbers merchant will have it. I used LD90
If you get a 'high speed' valve, these are held in place by a nut with rubber washers either side rather than the pull through rubber type. Drill a stop end and fit it to that. A place selling aftermarket alloy wheels should have them. When I installed my heating I used this idea with two pick up points for an in and gauge. Once happy there were no leaks replaced them with plain stop ends.
You can pump it up to a fraction of a bar with a bicycle pump and a lot of hard work to check for obvius leaks. I usually connect up to the mains water supply since that is about 3-4 bar around here which is a good margin above what a CH system will be running at in practice. After initial pressuring up and checking for obvious leaks you need to bleed the rads (or at least let some water into them) to catch leaks at the rad valves, otherwise slight leaks won't show up until the air has escaped and you may end up with a puddle on the floor several hours later when the water finally gets through.
For example, you'll likely never notice a leak that leaks 500ml/month, but it'll cause a sealed central heating system to lose its pressure in a few months.
If it's significantly below this - say 50ml/month, then if the boiler is being serviced annually, you'll probably never know.
If you get it airtight, it will certainly be watertight.
It should be airtight in any case, otherwise air leaks in (even when the water pressure is much higher than air pressure) and causes bubbles which can make a noise, and use up the inhibitor faster, possibly resulting in corrosion starting sooner than you's expect.
For maybe a bar of pressure, you've got 4Kg of force on a 22mm fitting. Over 3cm, this'll accellerate a 100g fitting to maybe 20m/s, if it comes completely loose, and has no attachment to the pipe at all.
Agreed. My own rule is that I pump with air to about 1/2 bar. If you can get that far then nothing has been forgotten. I'll then go up a little further say to 0.7 bar and leave it a while. If it holds pressure for 15 minutes then the air is released slowly (bleed valves) and the water is used. The only other way I can then have a puddle is when there is a joint that's not fully taken but the flux is holding it sound when cold.
I tested my UFH using a water pump and pressure gauge. Took it to 10 bar and left it at 6 bar overnight. Kept it at that while the screed went down. It cost me a fiver to hire the pump and gauge for a few days.
True, but since it's compressible, the leak of a small volume of air will cause a small reduction in pressure. For the same reason, you'll be pumping away forever at the foot pump to get the system up to test pressure.
Water is incompressible, so the leak of a small volume of water will cause a large pressure loss, usually all of the pressure very quickly. If you've used a pukka water test pump, a few strokes of the pump will usually get a system up to pressure, if you've got all the air out. If you're expecting it to pump up like a car tyre, it is easy to over-pressurize and damage the system.
The air pressure also varies a lot with ambient temperature changes. Air just isn't a very good medium for pressure testing, besides the safety aspects.
The Water Regulations specify a hydraulic test at 1.5 times the maximum working pressure for water supply pipes (OP has a CH system, so the Regs don't apply). For plastic pipes, two special test procedures are specified, because it expands gradually & slightly under pressure, causing a reduction in pressure. One procedure requires the system to be pumped up to the test pressure and the pressure is maintained by further pumping (as the pipe expands) for 30 minutes The permissible pressure drop is then nmt 0.6 bar for the next 30 minutes, followed by nmt 0.2 bar over the next 2 hours and no visible leakage.
Rehau (and other manufacturers, I'm sure) specify a similar test procedure for their plastic plumbing pipe.
Which is why you should have a gauge attached while you pressurise the system. However, most won't have many fittings hanging off the end of a pipe unsecured in some other way. Apart from in one of your 'installations' obviously.
Oops, I completely forgot about that aspect. If there is no pressure vessel, and no trapped air, then the only pressure held in the system is by virtue of expanding metal, and compressed water. So quite low volume to leak.
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