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

 

[Dotty]

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

All will be revealed when you do your ACS. Learn to walk before you try running.

 

[tamz]

There is no requirement to pressure test any existing pipework when doing alterations.

 

[jas88]

There is no requirement to pressure test any existing pipework when doing alterations.

I think there's a requirement to do some testing when the job quoted for was "fit the new cylinder, and check all the existing fittings since we're worried about the higher pressure" though...

But, according to this guy, you can't tell if a fitting's going to fail by inspecting it (probably mostly true) or by doing a pressure test or other test (the bit I'm very doubtful about). Apart from anything else, if he'd responded to the brief with "you can't test, changing to UV means a risk your fittings will suddenly burst and flood the house hours, weeks or months from now without any warning", he'd have been told to install it somewhere much darker and less comfortable for him!

 

[lame plumber]

if he had hydraulically tested you system and it had burst during the test, flooding your ceiling as now, who would you be claiming off for damages, or would you accept the damage as you asked him to test the system fully?

 

[tamz]

Believe me there is NO requirement to test when doing alterations to existing systems. Fitting an an unvented cylinder is an alteration to an existing.
New systems are different and should be tested to 1.5 times the working pressure.

There is always a risk of increased pressure finding out any weak points in a system. Getting someone else to do it wouldn't have changed the result. You would have still had a burst.
I would have had you sign a disclaimer before the work started or it wouldn't have started.

 

[jas88]

Is it not much more likely that burst would have been during an air test, though, with the plumber right there to deal with it, rather than in a potentially empty house? Even the hydraulic test, surely better under more controlled circumstances (with limited water) instead of an uncontrolled high-pressure flow continuing for however long it took to find and fix!

That disclaimer would have been a deal-breaker: no installation. With hindsight, obviously a better outcome, but this guy and the bathroom fitter were far too keen to go ahead, plonk the thing in and scarper. (Even leaving the logbook/guarantee paperwork blank, which doesn't help!)

 

[lame plumber]

if a disclaimer was a deal breaker then most firms wouldnt offer to do the work for you!

 

[tamz]

Plumbing systems are tested hydraulically. Air tests can be dangerous and require proper risk assessment and control measures.

If a test was offered this would be at an additional charge and any failings that showed up (testing by its nature is destructive) also chargable. Would you have been happy for the work to go ahead at a greater cost (and potential cost) if he had offered that and explained why.

Disclaimers and terms and conditions are a necessary thing these days (such is the way of the world). I don't need the hastle.

 

[jas88]

Plumbing systems are tested hydraulically. Air tests can be dangerous and require proper risk assessment and control measures.

If a test was offered this would be at an additional charge and any failings that showed up (testing by its nature is destructive) also chargable. Would you have been happy for the work to go ahead at a greater cost (and potential cost) if he had offered that and explained why.

The job as quoted - and indeed as performed - did include air testing, albeit only done at 1.5 bar which was apparently not much use, and with no mention of any risks involved. (Should I be concerned that I was sitting one sheet of plasterboard from most of the pipes concerned during the air test they did do?!) If a joint had burst during the test, even water rather than air, fixing that would be fine, and presumably any damage that might result too - after all, that's the situation I ended up having to deal with anyway, except without the plumber present and without any warning before the ceiling started dripping.

Disclaimers and terms and conditions are a necessary thing these days (such is the way of the world). I don't need the hastle.

Really, that's the bit I'm angry about. If I'd been told, say, "pressure-testing this properly will cost an extra £100, and might burst a pipe/joint, in which case that pipe/joint will need replacing" would be fine. Equally, being told it would cost £1000 to test and might mean a £10,000 repair bill would have been fine, though of course that one wouldn't go ahead.

If they'd just done the air test they did do at a higher pressure, like the 1.5 x 3 bar for new work instead of the 0.5x they used, am I right in thinking that would probably have caught the weak fitting which failed at 3 bar?

 

[tamz]

No one can say. It may have held up to a test ok as it did take a fair bit time before it came apart.
One of the downsides of plastic is when it leaks it is a big one rather than a drip.

 

[jas88]

You have a point there I suppose, having held up to 3 bar for 2 hours, it could well have held 4.5 for a few minutes and passed the test anyway...

Having just realised there was only six feet of air and nothing else between me and one of the plastic pipes under test, with hindsight and having seen your mention of danger, perhaps I should be happier about their use of low pressure! (Most of the pipes were above my head, with plaster in the way, but one ended in an open cupboard a few feet from where I sat, since your post was the first mention I've seen of any danger involved.)

Now you've piqued my curiosity about risk assessments and control measures, though - how should the air test have been done?

 

[tamz]

Ha If i tell you i would need to kill you :lol:

 

[tamz]

This will give you an idea

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

 

[jas88]

This will give you an idea

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

Thanks, interested reading - and a little worrying...

No more problems since Saturday (unless demanding an extra £160 to fill in the cylinder's logbook/guarantee paperwork counts!), which I'm hoping means it's all OK now.

The starting point was the need to get a second shower working on the far end of an ~ 8 foot run of 17mm copper under the floor. Rather than replace the copper - the floorboards were already up anyway - this guy suggested a UV cylinder as an alternative. The builder/plumber doing the shower room and I both had concerns about the existing bits, particularly the bathroom B&Q had fitted a few years earlier (the bit that leaked an hour after this plumber left!), so the job he was to quote for was changing to UV and checking/testing the existing fittings and the new bit. (Obviously, no mention at all of any danger or risks involved with testing; no mention of the air test until after the leak happened, just assurances the fittings had been checked and were all fine.) After it failed, they said the problem fitting was white rather than blue, which sounds like something you'd identify by looking at it?

How would you have done it? Swap the 17mm for something heftier and use a power shower (which had been the plan before the boards came up and the 17mm copper was visible)? (The pipe's perpendicular to the joists, which is a bit of a pain.) Go ahead with the UV cylinder?

 

[lame plumber]

wasnt leaking when he left, what more can you expect of a plumber. B&Q and their fitters are the ones to blame imho.