Test CH to mains pressure?

[405 TD Estate]

Before I tile over the bathroom floor and I have access to the plumbing under the floor I was thinking of connecting my gravity CH stytem to the mains pressure and that way if I have any leaks on the bits of plumbing I've just put in I can fix them easily.

I was thinking of doing this because at some point I will change (I won't say 'upgrade' now) to a combi boiler which I believe will run the CH at mains pressure.

So would I just need to connect the CH drain to my hosepipe and isolate the header tank?

If I were doing this I should also test the HW system to mains pressure but I cannot think how to do this - any suggestions?

[Andrew Gabriel]

No it won't. It will run at 1-2 bar, with a 3 bar pressure relief valve. Your mains pressure could be much higher.

You can buy a pressure test kit, which is pushfit (normally) adaptor with a tyre inlet valve and a pressure guage. You connect it up and pump up with a bicylce pump.

[Dave Plowman (News)]

I've recently converted to a sealed heating system which involved quite a few pipework alterations and there were no leaks at mains pressure. Cold, that is. Once it had heated up there were two... ;-)

[405 TD Estate]

screwfix has this dry pressure test guage

it requires pushing onto 15mm pipe and I don't have any 'ends' to push it onto, also wouldn't I still need to seal my header tank and if it leaks how on earth do you know where it's leaked? I think this is more for testing small parts of a system?

[Tim S]

405 TD Estate coughed up some electrons that declared:

You might be adapt it to a bit of hose onto a drain c*ck, held with a jubilee clip.

As to the header tank, do you have an isolator valve on the outlet to the heating system. If you've drained the system, good time to add an isolator. Likewise, if the hose onto a drain c*ck doesn't work, you could add a test point; eg a bit of 15mm sticking out of an isolator valve somewhere.

If the system is still full of water, freezing a plug of ice in the bit of pipe from the header tank would probably work (but make sure the boiler if fully isolated, gas locked off, power locked off etc or bad things will happen).

As to where the leak is - first see if you have any. Leak detection would them be done on a dry system using a similar approach to gas, but using a leak detector spray on each joint (or some whipped up Fairy foam). For a wet system, look for the drips.

My static mains pressure is 7.5 bar (that's high, 4-5bar is more common). The highest static rating I've seen for, eg a shower, is 10bar, so don't exceed 10bar as it wouldn't be reasonable to expect the system to cope much beyond this.

Cheers

Tim

[405 TD Estate]

Tim -

I guess your pressures are for the HW not CH and Andrew would be correct 1-3 bar CH for a modern combi boiler? But perhaps testing upto

10bar for the HW would be good.

This is starting to seem like a lot of effort for something I don't have yet (the boiler) however I guess it's a lot better than waiting until I need to put the boiler in and then hearing a leak under the tiled bathroom floor.....

[405 TD Estate]

Anyone know if its possible to get a wet pressure test kit? the screwfix one specifically says dry but since I don't know how to check for leaks with gas/air and looking for leaks would seem a lot easier, I also wonder if a tiny air leak would be detected but water could not escape through that air gap?

Is it normal to test the system dry? Should the system hold the pressure indefinately or loose so much pressure in a set time period and that's still OK? (i.e. some tiny leaks are acceptable)...

Could I some-how pump air in at the top of the system (so the guage is dry) and therefore pressurise the water - then I only have to look for leaks....

What is the chance my non-leaking gravity system will leak when exposed to 10bar HW and 2-3 bar CH?

[Roger Mills]

A combi *won't* run the heating at mains pressure - it will be lower. However, the heating system - including the radiators - should certainly be able to stand mains pressure, so you could use it to test for leaks.

Yes. You'd have to block off *both* the pipe which feeds the system from the F&E tank *and* the vent pipe.

No!!! Under *no* circumstances should you pressurise the existing HW system - assuming you've got a conventional HW cylinder. If you subject the cylinder to mains pressure, it will burst! [If you switch to a combi, that will run the HW system at mains pressure, but the cylinder won't then be there.]

[The Natural Philosopher]

> But it requires pushing onto 15mm pipe and I don't have any 'ends' to

I hired a hydraulic tester to test my UFH before screeding. Cost a fiver for a few days. Mind you that neede to have teh pipework filled, but its a good way to check plumbing.

IIRC I went to 10 bar on the heating circuits.

I don't think my mains pressure is much above 5 bar tho.

[Tim S]

Roger Mills coughed up some electrons that declared:

Ah yes - a very good point. Sorry I overlooked the obvious.

I would add, that if anyone wished to pressure test a system with a cylinder in place (even a little bit), do it wet, not dry. Same principle as steam engine boilers are pressure tested full of water (aka "hydraulic testing"). If it goes pop, then it goes pop and the loss of a little bit of water quickly reduces the pressure. Do it full of pressurised air, and it will go bang, with health-adverse consequences.

Cheers

Tim

[Tim S]

405 TD Estate coughed up some electrons that declared:

fine wet (I've got one).

If all the valves are sealing correctly it should hold up for long time. Gate valves might be a problem with a dry test - I can see them leaking air.

*** But please heed Roger's warning regarding HW cylinders (or any large volume device attached to the plumbing). ****

Think you'd be better off with a wet test if you can arrange it. Or mostly wet, with a little bit of air from a foot pump just to bring the HW pipe pressure up to the test point for that test only.

How good does the plumbing look?

Cheers

Tim