Push-Fit Disaster

[DaydreamJay]

In fact, I'm still not sure what point you are making.

My point is that I don't see anywhere in this particular design that the pipe is less secured if not pushed all the way to the end, all it has to do to be secured is pass the grab ring surely?

I am not arguing for the sake of it, I am just trying to find out a possible cause, the marks on the pipe showed that the grab ring slipped about 25mm along the pipe before disengaging.

 

[Softus]

Its apparently a case of the pipe pulling out of the tube.

Thats why I would normally use soldered copper for all pressurised pipework.

That's just b*llocks, because all pipework is pressurised, and you've previously described a case of you having used push-fit fittings, and found it "too easy".

Yet another example of why NOT to use plastic !

So remind me - what were all the other examples?

The example it does provide, yet again, is of you using the wrong terms to claim something you have insufficient data to support.

Plastic is a material, not a type of fitting.

Push-fit is a type of fitting, which can be either plastic or copper.

A fool is a type of person, who believes something based on personal prejudice.

Propaganda is dissemination of a prejudice in such a manner as to make it look like fact.

 

[Softus]

My point is that I don't see anywhere in this particular design that the pipe is less secured if not pushed all the way to the end, all it has to do to be secured is pass the grab ring surely?

The word "surely" betrays an assumption. It's a wrong one.

It's clear from taking one glance at a fitting that the pipe is fully supported, axially, only by full insertion into the fitting. Partial insertion allows the pipe to wiggle, which, if done enough and/or for long enough, can wear the O ring and stress the grab wedge. This much is obvious to me, without being a hydraulics engineer.

I am not arguing for the sake of it, I am just trying to find out a possible cause, the marks on the pipe showed that the grab ring slipped about 25mm along the pipe before disengaging.

Well, if you want help in finding the possible cause, then the sensible steps would be as follows:

1. Post a photo of the disassembled parts of the fitting, and of the end of the pipe.

2. Measure the pipe diameter and compare with the spec.

3. Measure the grab wedge diameter and compare with the spec.

4. Verify that the end of the pipe was cut cleanly and squarely, and was not squashed. Bear in mind that squashing can occur if you don't rotate the pipe (as per the MIs) when cutting it.

5. Confirm that the pipe was made by Hepworth, and was not some inferior or incompatible brand or type.

Or, you could apply wishful thinking, make a bunch of groundless assumptions in a limp attempt to support the view that it was manufacturer error, and join the ranks of the "copper only" brigade who, presumably, campaign in their spare time for the wholesale replacement of MDPE with copper.

 

[DaydreamJay]

Softus, take your butt-plug out for a minute and sit down and read. I am not trying to level any amount of blame at the manufacturer, I am merely trying to find out what the possible causes of this accident were and how I can avoid them in the future. You are obviously on a power trip and your arrogance shown to other posters in this thread is unbelievable.

You're a proper keyboard warrior in every sense of the term.

I am not convinced that an incomplete insertion of the pipe into the fitting has any bearing on whether it would blow the pipe off or not, I am not saying it would or wouldn't but there is no evidence to suggest it would. What an incomplete insertion would do however is mean that the fitting leaked and it did not leak prior to coming off.

Maybe when you've stopped being so pompous you can post in a more coridal manner and stop insulting people.

 

[Softus]

Softus, take your butt-plug out for a minute and sit down and read. I am not trying to level any amount of blame at the manufacturer, I am merely trying to find out what the possible causes of this accident were and how I can avoid them in the future. You are obviously on a power trip and your arrogance shown to other posters in this thread is unbelievable.

....and there it is. Are you capable of debating without being insulting?

And if you think my post to Agile warrants abuse from you, then maybe you should read all of the arrogant, misguided, socially judgmental, presumptuous and incompetent (when not talking about boilers) nonsense that Agile has come out with over the years. It would be a mistake for me to upset the delicate equilibrium of the forum by suddenly not telling him when he's cocked up.

You're a proper keyboard warrior in every sense of the term.

I choose to take that in the complimentary way that I'm sure you didn't mean.

I am not convinced that an incomplete insertion of the pipe into the fitting has any bearing on whether it would blow the pipe off or not, I am not saying it would or wouldn't but there is no evidence to suggest it would.

In that case you aren't experienced enough to make that judgment. You can rectify that mistake by looking at a fitting and reading the manufacturer's documentation.

What an incomplete insertion would do however is mean that the fitting leaked and it did not leak prior to coming off.

I disagree, and I've already described what is likely to happen as a result of incomplete insertion. If you think that description is invalid then so be it, but pretending that I didn't write it seems to be something less than a a genuine attempt to understand. I can't predict precisely what effect ignoring the MIs will have, other than to invalidate the warranty.

Maybe when you've stopped being so pompous you can post in a more coridal manner and stop insulting people.

I haven't levelled any criticism towards you, but if you feel that the cap fits then I'm sure you'll look good in it.

And I'm not being pompous - I can assure you that you'd know it if I were.

 

[DaydreamJay]

If you say so, since I can't predict precisely what effect ignoring the MIs will have, other than to invalidate the warranty.

In that case you aren't experienced enough to make a judgement on my incident, but thanks for trying and don't feel bad about it.

 

[Softus]

I find no shame in not knowing the things that I don't know, and at no point have I attempted, or implied that I've attempted, to make a judgment about your incident.

I offered you information about the fittings. If you don't want the information, or don't like the way it was presented, and therefore prefer to ignore it, then it's your loss, not mine.

Naturally you're at liberty to verify it, or seek it elsewhere or by other means, but you won't find that I'm wrong, because I've posted only facts, whereas you've posted nothing but opinions.

 

[DaydreamJay]

I find no shame in not knowing the things that I don't know, and at no point have I attempted, or implied that I've attempted, to make a judgment about your incident.

Where did I say that you had made a judgment? You are obviously easily confused - I said that you aren't qualified to do so, not that you had done so already.

I offered you information about the fittings. If you don't want the information, or don't like the way it was presented, and therefore prefer to ignore it, then it's your loss, not mine.

You offered me obviously biased information if your vitriol aimed at people who prefer copper fittings is anything to go by

Naturally you're at liberty to verify it, or seek it elsewhere or by other means, but you won't find that I'm wrong, because I've posted only facts, whereas you've posted nothing but opinions.

Thanks, I will, you seem to be universally disliked by everyone on here anyway so I'll not waste anymore of your time or add to your one man crusade.

 

[Softus]

I find no shame in not knowing the things that I don't know, and at no point have I attempted, or implied that I've attempted, to make a judgment about your incident.

Where did I say that you had made a judgment? You are obviously easily confused - I said that you aren't qualified to do so, not that you had done so already.

No - I didn't say that you said I had made a judgment, so you are the one who's confused, or not reading carefully.

I said that I hadn't attempted to make a judgment, in response to you thanking me for "trying".

I offered you information about the fittings. If you don't want the information, or don't like the way it was presented, and therefore prefer to ignore it, then it's your loss, not mine.

You offered me obviously biased information if your vitriol aimed at people who prefer copper fittings is anything to go by

It isn't anything to go by, so by your own logic my information was not biased.

If you'd like to point out which part of it you think was biased, as opposed to just regarding anything I wrote as being biased, then please do, and I'll explain why I believe it to be based in fact.

As well as information about the fittings, I suggested to you some measurements to take to further your investigation. The suggestions were sensible ones, but it seems that you've become so annoyed by my post to Agile that you're ignoring all the helpful things and are intent on reiterating the insults. As I said before, you're the only one who stands to lose by ignoring the help.

Naturally you're at liberty to verify it, or seek it elsewhere or by other means, but you won't find that I'm wrong, because I've posted only facts, whereas you've posted nothing but opinions.

Thanks, I will, you seem to be universally disliked by everyone on here anyway so I'll not waste anymore of your time or add to your one man crusade.

No crusade, and I'm not here to be either liked or disliked. If you prefer to bleat along with the rest of the flock, then so be it, but rest assured you haven't wasted any of my time.

 

[ChrisR]

Chris, if the pipe can move into the fitting after installation then it hasn't been fully inserted.

Wrong. You push the pipe in until it stops. Force not specified. So if you pushed harder, the materials would elastically deform more and you'd have the pipe in a bit further.
Then you do the unspecified "tug". That moves the pipe out of the fitting, some distance or other. At some unspecified point the grab ring does its thing and moves with the pipe, digging in to it. Your tugging elastically deforms the materials, so when you let go, things move back.
So now you have a pipe in a fitting which can move. It can't move much, but it can move. (This is the point Speedfit addressed with the twist-lock).

Then the temperature cycles, and the water pressure cycles, and the different materials move in relation to each other. The metal in the grab ring will move in relation to the grab ring it sits in, the grab ring in relation to the pipe, and so on.

There aren't many installation variables. The pipe could have axial or radial tension, but Hep should have tried all ranges of those.

The method relies on the friction between the pipe and the grab ring being sufficient to make the grab ring move with the pipe when it's pulled outwards from the fitting. If thr pipe can move at all without the grab ring, EVER, it'll come out.

So I would say it's a Fitting design error, damaged component, or manufacturing fault.

 

[Gasguru]

Yet again Hepworth proves itself to be a flawed system.

One day insurance companies will see sense and refuse to offer cover on these carp systems...it can't happen sooner IMHO.

 

[Softus]

Chris, if the pipe can move into the fitting after installation then it hasn't been fully inserted.

Wrong.

Firstly, that statement of mine was in the context of full or partial insertion at the time of installation, so I believe it to be correct in that context.

You push the pipe in until it stops. Force not specified. So if you pushed harder, the materials would elastically deform more and you'd have the pipe in a bit further.

I agree with that theory. However, the additional force needed to compress the pipe longitudinally is far beyond anything I could apply with my hands, and if I tried then I would squash the pipe with my grip before it moved further into the fitting.

Note the importance of cutting the pipe squarely - if you don't, then less of the pipe is retained laterally, and more movement will result. Also, with a high insertion momentum, the lip of the insert could be deformed at its reduced area of contact with the end of the pipe, equating to partial insertion. Note also the importance of not deforming the pipe radially - if you do, then you could expect more lateral movement during temperature and pressure changes.

Then you do the unspecified "tug". That moves the pipe out of the fitting, some distance or other. At some unspecified point the grab ring does its thing and moves with the pipe, digging in to it. Your tugging elastically deforms the materials, so when you let go, things move back.

That would be my view of what happens too. You can hear the result of a similar, if not identical, effect of this by livening the supply to installation at a reasonably high pressure, say at 10 bar. The assembly creaks as the water forces the grab wedge into the taper of the capnut, with the result that it grips harder onto the pipe.

So now you have a pipe in a fitting which can move. It can't move much, but it can move. (This is the point Speedfit addressed with the twist-lock).

Then the temperature cycles, and the water pressure cycles, and the different materials move in relation to each other. The metal in the grab ring will move in relation to the grab ring it sits in, the grab ring in relation to the pipe, and so on.

I don't disagree that movement is possible, but determining whether the pipe is moving through the grab wedge, or whether the pair of them are moving together, is something that needs more data anyone who's posted here so far claims to have.

It could be argued that, if Speedfit grips the pipe more effectively that Hep2o, the stresses that result from temperature and pressure changes are not dissipated as effectively. I don't know the answer to that one. I don't know if Speedfit is better, or has fewer instances of failure, than Hep2o.

There aren't many installation variables. The pipe could have axial or radial tension, but Hep should have tried all ranges of those.

The method relies on the friction between the pipe and the grab ring being sufficient to make the grab ring move with the pipe when it's pulled outwards from the fitting. If thr pipe can move at all without the grab ring, EVER, it'll come out.

I don't have enough information to agree or disagree with that. However, if a product design is such that the failure rate is acceptably low, then that design can be deemed to have been successful. I don't know what the rate of failure is, and every attempt I've made on the forum to solicit information from people who report failures is met with the now commonplace derision aimed at people who don't pledge lifelong allegiance to copper.

An analogy might be the number of complaints that the general public makes about the police force. There are lots of outraged forum members when things go bad for the police, but very few of those (only one, AFAIK) postulates that the very existence of the police force, in its current form, is A Bad Thing.

So I would say it's a Fitting design error, damaged component, or manufacturing fault.

That's a valid list, but incomplete. It could also have been installation error.

I don't know where to find the statistics that would show a comparison between longevity of push-fit fittings compared to soldered fittings. I don't believe that Hep2o O rings will last forever, but I know that copper doesn't.

Another factor that could be theorised about, without any hard data (but that's never stopped us), is the general stigma about the use of plastic pipe and plastic push-fit fittings. In my experience, long-term users of copper and solder tend to favour its continued use over newer materials, and I have no problem with people feeling more comfortable with what they know best, because all learning carries a risk of an increased rate of mistakes. But the result of this is that push-fit tends to be used by many people who don't care about the stigma because either (a) they don't care about their work, or (b) because they're not the person making the decision about the materials. In either of those cases the rate of installation error is, IMHO, likely to be higher than it would be in the hands of more experienced, or caring, installers. This skews the statistics in the direction of a higher failure rate.

Plenty of builders still use solder, and enough of them do such a poor job that I still go to at least one job a week where the copper has corroded right through as a result of all the flux, copper shards and iron filings that remain inside the pipework through sheer laziness or incompetence.
_________________

Yet again Hepworth proves itself to be a flawed system.

It's frequently stated on the forum that no properly trained, competent, professional plumber (or heating engineer, or whatever) would ever use push-fit. If this is true, then it's easily argued that the only people using it are improperly trained, or incompetent, or unprofessional, or any permutation of those.

And if that really is the case, then I would expect the failure rate of a poorly designed and manufactured product to be failing in most installations. So if that's true, then it's testimony to the design and manufacture that such a system can be fitted, badly, by idiots, with what nobody has shown to be more than a fraction of a percentage of failures.

If you're going to hoist a petard, you should retire to a safe distance.

One day insurance companies will see sense and refuse to offer cover on these carp systems.

Those dratted insurance companies - they just won't see sense, will they! If only they would ignore the industry statistics and instead listen to a bunch of narrow-minded bigots, everything would be OK.

 

[Doctor Drivel]

Also, it's a stupid question but is there any device that is available that would protect against this sort of thing?

Yes. AVOID PUSH-FIT fittings!!!! When they go, it is usually in a big way.

 

[Softus]

Well it goes to show that DD does have one use, which is remind that I hadn't attempted to answer that question.

Also, it's a stupid question but is there any device that is available that would protect against this sort of thing?

You could fit one of these:

http://www.watersave.com.au/WaterGuard/default.asp
http://www.safehomeproducts.com/shp...lfields&allfields=floodstop&from=default_left

Just a couple of ideas; there might well be better ones. (Not a heat bank though.)

 

[Agile]

Then you do the unspecified "tug". That moves the pipe out of the fitting, some distance or other. At some unspecified point the grab ring does its thing and moves with the pipe, digging in to it. Your tugging elastically deforms the materials, so when you let go, things move back.

I dont think thats meant to be the case!

The unspecified "tug" is to cause the beginning of a toggle action by the grab ring which I think is intended to cause it to actually bite into the surface of the tube!

Only when it has mechanically deformed the tube, however slightly has the fitting become locked to the point when it will not come out under any normal operating conditions.

I would expect this apparently unexplained failure might have been as a result of incorect insertion and tugging.

However, the fact that there are several marks on the tube cause me to wonder if it has been incorrectly inserted and was then opened and remade. The manufacturers mostly say that should not be done!

I have never had a plastic joint that I fitted fail but I have been to repair many made by others! I always mark the tube first even though I think that I can tell when its fully inserted!

Tony