Errrmmm... quickie workshop plumbing question

[misterfish]

i know of a case of a claim against Speedfit where on a extension 6 months on from completion whilst the couple were away a fitting failed. Upon their return, the house was flooded minus a ceiling. the result after the contractor getting the speedfit manufactures in, was a charge against speedfit, which they then paid out for the repairs after examining the fitting in question.

What about a comparison with copper - I know of failures with this system as well - I've had minor failures of a couple of fittings over the years which I've picked up on myself. Currently our house uses both plastic with pushfit joints and copper with both soldered and compression joints and they all work fine.

Anything I do now is in plastic.

Misterfish

 

[RogerS]

And with plastic there's less for them to nick if you're doing a major refit and not on site 24/7.

And you don't need to fuss too much about bonding earthwise if it's all plastic. Nothing to bond too.

 

[wobblycogs]

I've probably read just about every bit of literature that JG currently produce and I've not once seen any mention of pressurizing the system to ensure the connectors bite properly. The SpeedFit connections (at least) have one way teeth, once the pipe is pushed in the teeth bite more firmly the more you try to pull the pipe out. The only way to get the pipe out again is to push the release ring which holds the teeth back, even then it can sometimes be tricky to remove the connector. For the paranoid there's also a locking nut which locks the release mechanism so their can't be any accidental releases.

I agree that plastic systems haven't had as long in real world tests but there are certainly plenty of systems that have been installed for 15 years and more. If they aren't showing any signs of failing I have to believe that the there's probably not that much wrong with the system.

 

[ondablade]

Thanks on the bending Mark, i've gone with fittings having discovered for myself the limits of springs.

My suspicion is that it's probably possible to get a problem with push fit fittings as a result of bad assembly - e.g. as a result of not pushing it fully home.

I wonder how they do too if a 90 deg change in pipe direction means that expansion and contraction result in regular twisting of the joint.

That said a quick calculation suggests that 30psi pressure in a 1/2in pipe will produce an axial pull of about 6lbs which should do them up tight. (?)

10bar is almost 150psi Mark - that's a lot of pressure, but on the other hand the stuff is apparently certified to be OK to a max of this on cold water.

The various Agrement boards have it as certified up to 50 years life too on cold water, but reducing fairly rapidly with increasing temperature - so that it's only OK for short exposures to 100 deg C.

Solder fittings can leak too if the soldering technique is not good, and compression fittings due to assembly errors.

It'd be interesting to know if there are real cases of proven failures out there on correctly installed systems that where there were no manufacturing faults - if the horror stories are backed by fact.

Despite all the elder lemon 'experts' in the business (it's instructive to look up a plumbing forum on something simple like how to do up a compression fitting - every answer is different) when i see what the trade gets up to in practice with compression fittings (e.g. mixing metric and imperial pipe and fittings) it's a minor miracle that every house in the country isn't knee deep in water.

My suspicion is that they are not because basically all of the systems not only work, but are highly resistant to variations in technique....

 

[wobblycogs]

When we started using push fit I, like a lot of people, didn't trust it so I did some tests of my own.

The first tests I performed was to push the fitting on and take it off the same piece of pipe multiple times to see if it would fail. I gave up when my fingers started hurting and the fitting showed no signs of failing.

I've then deliberately turned the pipe in the fitting to see what damaged it would cause. The locking teeth did score the pipe but only like they do when the fitting is normally pushed on. Both of these tests were performed on pipe that was then subject to 3 bar cold water pressure.

Finally, I had an old copper cylinder so I put it outside on the patio and filled it with water. I connected a straight 22mm coupler to the inlet at the bottom (to maximize the pressure on the joint) and a tap to that then left it to stand in the elements - the coupler was south facing so got full sun. After 18 months there wasn't the slightest sign of a leak and the plastic looked fine if a little discoloured. I would still be running that test but some git stole the cylinder!

The only leak we have had from push fit is with a stop end that wasn't pushed home properly and boy was that funny

 

[sparkymarky]

obviously i was going to tickle a few peoples nerves with my last comment, however from my point of view using pushfit plumbing takes away the skill of professional plumbing.
also using plastic pipe on hot water and heating systems in my mind is a very bad idea, as the coefficient of linear expansion is much greater with plastic tubing (see table on the bottom of this page http://www.pipestock.com/ABS-Specifications.php) and the pipes will sagg therefore causing stress onto the fittings which join it unless the pipe is cliped every 30cm or so.
like everything pushfit has its place, but would anybody here be happy to have drawers screwed together rather than dovetailed. just because its easer and quicker to make a drawer with screws, yes it will do the job and it could possibly stay together as long as a dovetailed drawer, but ultimatly the dovetailed drawer would be everyones first choice if they took the time to learn how to do it properly.

 

[wobblycogs]

Properly, to my mind, is whatever is the best solution for the current job. In the case where you are making a heirloom quality piece of furniture you probably would dovetail the draws. If you are making furniture that is likely to be thrown away in <10 years when fashions change the proper jointing method is something like a pinned and glued butt joint.

Expansion along the length can be an issue for plastic pipe but no one said it was an exact drop in replacement for copper. The recommendation is, IIRC, to not clip it any more than every 500mm. That way the expansion is taken up in slight (temporary) bends between the clips rather than being forced all to the end. Cosmetically it doesn't look as good but I for one don't spend my time looking at the plumbing.

I've plumbed in both copper and plastic and I would now choose plastic every day, its fast, flexible, fairly cheap, pretty much silly person proof and as far as I can tell reliable. That makes it a no brainer from where I'm sitting.

 

[ondablade]

I'm not be quite so idealistic as that in my choice mark. I'm no 'plumber', but my recent approach has been to use copper where it's visible/ i care about the looks. Plastic for stuff where the flexibility is useful in getting stuff lined up or connected, for example on runs through joists.

I'd not so far worked up the courage to go with push fittings, but in order to get one compression connection done up on a plastic pipe on the current job i had to cut out and lift a section of floor - where i could have done it in minutes with a push fitting. Based on the feedback here it sounds like it's only a matter of time before i capitulate Wobbly..

I wonder if there has ever been a proper study done on the relative reliability of the various systems - by somebody that's reasonably independent??

 

[RogerS]

To be honest, Ian, hep2o has been going for nearly 20 years as far as I know. If the concept of push-fit was dodgy then there wouldn't have been all those jumping on the bandwagon.

The other nice thing about pushfit is that the joints can rotate...makes final tweaking/plumbing simple when needed.

 

[Chems]

system must be pressurised to 10 bar to ensure the fitting grips the tube properly, many people dont and the fittings tend to blow off or leak after a few years (john guest recomend this).

Thats crazy, in the Fire service we test out hose to 10bar, and thats running the pump and nearly full tilt and produces such power at the hose end its a struggle to control it. I don't think anyones house is going to be subjected to that sort of force, not unless the occupants have explosive poop!

 

[jams]

system must be pressurised to 10 bar to ensure the fitting grips the tube properly, many people dont and the fittings tend to blow off or leak after a few years (john guest recomend this).

Thats crazy, in the Fire service we test out hose to 10bar, and thats running the pump and nearly full tilt and produces such power at the hose end its a struggle to control it. I don't think anyones house is going to be subjected to that sort of force, not unless the occupants have explosive poop!

Push fit or speed fit collars work on 'reverse pressure' so the 10 bar pressure test , primarily checks for leakage ,but also seats the collars nicely by pushing them backwards