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.

 

[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.

 

[jas88]

wasnt leaking when he left, what more can you expect of a plumber.

Honesty!

When specifically asked if the existing fittings would cope with the much higher pressure, the plumber recommending it could have given one of the answers others have posted here, that it's not possible to be sure, or that being nearly-sure risked causing a water leak in itself - instead, he said it would be fine and that he'd check the fittings could cope as part of the job. Not the slightest suggestion of any risk involved, quite the opposite. That, legally, morally and IMO professionally, is where he screwed up badly. (As he has since admitted, to be fair, and done what he can to put it right; after a little lawyering, it sank in that both parties had had a narrow escape.)

I would be grateful if someone could clarify their explanation about white v blue fittings, which sounds like something immediately obvious with even a brief glance at the fittings they were supposedly checking as part of the job quoted for. I posted this question here because they were hiding behind their 1.5 bar air test as being enough to support their assurances; as a physicist that sounded like nonsense, so I wanted the plumbing view. (It sounded to me a lot like "I tested this car's brakes at 30mph, so it must be fine for motorway use", "this extension cord's tested for 110V at 15 amps, so I'll use it for your 30A 240V ring main and hope it's OK"...)

B&Q and their fitters are the ones to blame imho.

They did a poor job*, perhaps, but their work held up fine as installed for years: it was only after this outfit made the change they'd promised would be OK that there was any problem. Legally (per Trading Standards lawyer), B&Q are off the hook there unless the "white" fittings (whatever those are) are actually prohibited for plumbing use: the increased pressure is a 'novus actus interveniens', not to mention this outfit's breach of contract by not even glancing at the fittings. Tell a customer about a risk and make sure they understand and accept it, that's one thing: sell them something and promise you'll do something that avoids the risk you ignored and they asked about, you are in for a whole world of pain when you let them down.

I had eye surgery last year. There was a detailed consent form explaining the risks and possible side-effects or complications (as standard for medical procedures), and I discussed the risks and how they would be reduced and dealt with if necessary beforehand. It wasn't a perfect outcome - but they didn't promise one, and did take the appropriate steps we'd discussed beforehand to address them. When you risk flooding a customer's house, potentially causing structural damage and tens of thousands of pounds of damage, shouldn't you tell the customer first?! The plumbers on this thread all seem to agree on that point at least.


Bottom line: shouldn't getting paid to "check those fittings, particularly the bathroom ones" involve at least seeing them? Wouldn't a proper plumber admit to the risks of much higher pressure when asked?

* It included fly-tipping in the garden: dumping a used bathroom suite from their previous job round the corner, to pick up later and save on disposal fees, as well as breaking a phone socket. Not impressive stuff, but at least the ceiling was still dry afterwards, unlike this unvented cylinder fiasco.

 

[lame plumber]

best you can do now is to replace all the shoddy fittings and pipework as youll never know if its going to fail in the future