Pressure testing - 1.5 bar enough?

[jas88]

Just had an unvented hot cylinder installed this morning, replacing a gravity-fed system ... now waiting for the bathroom floor and kitchen ceiling to dry out.

Apparently, the push-fit hot water connection on the bathroom sink wasn't up to the higher pressure, so it burst and flooded the house an hour after the electrician left (he connected the new cylinder's thermostat, having some difficulty, so he was left for a while after the plumber had moved on to his next job).

The cylinder change was suggested by the guy fitting a new en suite shower (17mm pipe, gravity fed, not much pressure) - who found a plumber (Gas Safe, I know - the cylinder's heated by a gas boiler) and specifically told the guy to test all the fittings to be sure they could handle the higher pressure. He said this would mean taking the side panel off the bath etc, to check all the fittings were OK.

When called back to fix the leak, I was assured the 1.5 bar air pressure test was enough, there was no need to inspect the fittings and no way to know one of them would fail an hour or two later, it's an "act of God" (as the plumber's boss put it). He reckoned the mains head is about 3 bar, but blanked me when I asked "why only test at 1.5 bar then?"

I'm no plumber - I've done some wiring, the day job's computing - but it seems to me you should test with more pressure than the expected load, not half! Is it just hindsight, there was really no way he could have known the fitting would fail later and a higher pressure test would be pointless? A quick search on here brought up mention of much higher test pressures, so I wanted to ask more specifically in this case.

 

[supper plumb]

up to 3 bar and let it settle for 5 mins then set your marker needle to that and leave if for 30min 60min any drop then check for leeks.
was it a water test or air test????

id not have any push fit fittings on my pipe works unless it was all plastic

 

[jas88]

Air, they said. To be fair, it held up to the mains water pressure (guessed at 3 bar) for about two hours, so it would probably have held up for half an hour at 3 bar of air too, wouldn't it?

 

[supper plumb]

i dont know loads about testing sorry but the guys will be along soon to help but id say water test over air any day

 

[GQuigley67]

Generally testing is 1.5x the standing pressure

 

[jas88]

Thanks, that was the impression I was getting here - i.e. they should have tested to more like 4.5 bar, not 1.5. Corner cutting?

(To add to my worries, I look on GS - and they are registered ... but, according to the website, NOT for unvented cylinder work, only vented. Out of date web content, or has someone been naughty there? I'm guessing Gas Safe don't list "qualified for X, Y and Z" for amusement purposes?)

 

[GQuigley67]

Dont worry, i had to ask GS to put my unvented on, they are probably still qualified just not on their GS card.

 

[supper plumb]

id like to know how do you pressure test a new gas pipe run am i right in thinking its a air test not water???

 

[GQuigley67]

Water? No of course not, air pressure test.

 

[hammers4spanner]

any plastic involved belt it upto 18 bar , anything else 1.5 times

 

[GQuigley67]

Wen i say air pressure test its gas pressure i.e mbar not bar

 

[GQuigley67]

18 bar? I thought most manufacturers recommended 10?

in the real world i just water test it

 

[hammers4spanner]

yep 18 bar makes the rings grip properly

 

[supper plumb]

yer like testing your CH pipe work?? wet test do you wet or dry test for gas runs????

 

[hammers4spanner]

not sure about new hep tho that maybe different

 

[Simon F]

(To add to my worries, I look on GS - and they are registered ... but, according to the website, NOT for unvented cylinder work, only vented. Out of date web content, or has someone been naughty there? I'm guessing Gas Safe don't list "qualified for X, Y and Z" for amusement purposes?)

the cylinder installation is subject to needing notification to building control,
so if it has been done and registered properly you will be getting notification come through the post within a few weeks,
from what you have said, don't hold your breath on that one!

 

[GQuigley67]

yep 18 bar makes the rings grip properly

Aaah, i dont use plastic so not too sure

 

[jas88]

It's not the gas pipe, this is the (hot) water that failed. Copper under the floor, soldered, plastic at the ends into bath/sink etc. (Some silver lining there I suppose, if the gas pipe had leaked I'd have bigger worries now than a wet light fitting and floor/ceiling...) They've taken the wet kitchen light fitting down - their guy's coming to replace that tomorrow or Monday depending when he can get the replacement.

With hindsight, the Perth company that did some work here a few years ago is listed as unvented qualified, so I'd have at least given them a try. Trouble is, the bathroom fitter (non-GS reg, not many gas-powered bathrooms I suppose) was mid-job and announced we needed the cylinder replaced this week so he could complete on time next week, and brought along this guy to do it.

Might it be worth getting somebody in to drain it down and test at a more useful pressure than 1.5 bar, or can I rely on the fittings that will fail already having done so by now?

 

[lame plumber]

should be talking to whoever put the failed plastic fitting on, as all my convertion work states that any problems with current pipework are at customers own risk after all any pipework new or old should be capable of withstanding 10 bar, its all the same components after all,

 

[glenno1]

Test plastic as you would do copper it should be capable of holding 7 bar of pressure as it says on the pipe