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By SimonG
#1627
A lot of people have had flexible connectors burst or leak. Some may even think of them as the devils work.
But I find them useful and a lot of taps now come with flexies rather than hard piped.

The important things to remember are.

Don't kink the connector when installing. It will create a weak point and disrupt the flow to the tap.

Don't allow the connector to twist. It will stress it and potentially lead to failure.

Don't fasten them directly onto isolating valves. The rubber on the connector can be cut on the chamfer of the isolation valve. Fasten a spare radiator tail into the isolation valve first. This gives a flat surface for the connector to seal too.
By jonnyswamp
#1796
I recently changed a split flexi in a dentist surgery in Cardiff
It burst on a Friday evening (upstairs patients w/c) and run full bore until it set the fire alarms off in the morning (caused a short probly)
Don't know the final figure, but it includes most ceilings, downstairs floor coverings and 2 dentist chairs at around £30,000 each
So if they are used, follow SimonG's advice and also check them now and again as you will sometimes see signs of bulges or fraying braid before they burst
User avatar
By REDSAW
#3658
YorkshireDave wrote:
September 29th, 2017, 10:37 pm
Does anyone one else have a problem with the advertised bore of these?

If advertised as a 13mm bore what would you expect the bore of the hose to be?
half inch?
By joni os
#3670
The cross section area is the important criteria. A circle will always give a greater cross section area than an oval of equal perimeter. Bends create non circular cross sections. Flexis are used where bends are necessary hence the problem. In many cases I find a length of Hep2O with push fit couplers will perform better than a braided flexi. has the advantage of being cut to the correct length, rotates freely at connections and being readily available (length of pipe and connectors in van) works out cheaper. Where possible a properly bent copper pipe will always be the superior solution.
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By YorkshireDave
#3671
Quite agree. Perhaps however I should come clean. Fact is if you have a 100mm dia pipe that drops down to 10mm then goes back up to 100 its bore is 10mm due to the limitation to flow.

All of these flexies mention a bore that relates to the rubber hose ONLY. When you measure the minimum dia of the fittings at the ends they drop to closer to 6mm. So, we are being lied to at best and ripped off at worse. :x :x :x
User avatar
By Best
#3678
Same with modern bath taps on gravity supply, - old taps had 3/4" works and full flow, but the new taps with 1/2" works just don't flow the same. We are being ripped off with inferior products.
As to flexis - I had to replace a burst flexi on mains last week that was connected to a monobloc 15mm pipe. It appeared ok and not twisted and not bent much. I just machine bent a 90 degree piece of copper pipe and used a 15mm compression elbow and it took just 5 minutes to install. I can't see the reason to use flexis where a copper pipe, or plastic pipe would do better job.
User avatar
By REDSAW
#3682
AH!, yes on the tap connectors it goes down to about 6mm.
the straight connectors bores are all through sized.
i like the idea of using plastic on toilet connections instead so i may try that next time on a twisty fit.

i believe also those hoses split after the stainless braid wire is twisted-brakes a strand then perforates the rubber lining causing a pressure rupture.
User avatar
By YorkshireDave
#3697
joni os wrote:
October 1st, 2017, 12:12 pm
Following above logic a 12 bore shotgun with full choke would not be a 12 bore. Even worse the," less aware," could claim a gas boiler with 15mm gas connection only needs 15mm pipework from meter.
Joni. Get your point but disagree with the outcome.

Fact is, YOU as the owner choose to choke your 12 bore. When YOU remove whichever choke you are using the gun goes back to being a 12 bore or 10 if you're a bit younger.

These flexis are advertised as being 13mm and they charge more for the larger bore. And yet, the real, unchangable bore is, as I've already said, closer to 6/7mm which patently limits flow permanently vs a 13mm bore. Oh, as if you didn't know, we are talking a completely different issue with gas so that's a red herring. Just chuck it back in the sea where it belongs...

We are being charged for something almost none of these flexible hoses deliver. Personally I do not feel that is right and proper as I don't want to rip my customers off and neither do I wish to be ripped off. If you are happy with that that's between you and your customers/bank manager ;)
User avatar
By YorkshireDave
#3698
Best wrote:
October 1st, 2017, 1:40 pm
Same with modern bath taps on gravity supply, - old taps had 3/4" works and full flow, but the new taps with 1/2" works just don't flow the same. We are being ripped off with inferior products.
As to flexis - I had to replace a burst flexi on mains last week that was connected to a monobloc 15mm pipe. It appeared ok and not twisted and not bent much. I just machine bent a 90 degree piece of copper pipe and used a 15mm compression elbow and it took just 5 minutes to install. I can't see the reason to use flexis where a copper pipe, or plastic pipe would do better job.
Dont get me started... Once again this is corporate avaris taking advantage of the fact that there's no formal definition of low or high pressure for a domestic water environment. There is a 'level' of consensus that open vented systems are 'low pressure' but there is no legal definition, no upper and/or lower limits. It's for this reason a tap manufacturer can say 0.5 bar is low pressure. Some poor homeowner puts a 0.5 bar tap in a bathroom with the CWS just above on the joists and they find they can pee faster but they have no comeback...

Some 'after market' cartridge manufacturers, can think of one not yet on the market, have specifically designed their cartridges to truly maximise flow through them. That said, the fundamental design was driven by a Yank where, of course, hot water systems are high pressure. They never designed them to take over in low pressure circumstances. It was lower cost to manufacturer and inbuilt obsolescence that drove their use to today's levels. Sorry! History lesson over.

Tap manufacturers buy on two principal criteria - looks and price. With the exception of some Pegler taps, the rest don't give a flying fig about performance. Their view is 'state the minimum operating pressure (NOT optimum) and let the mugs (sorry buyers) beware'.
User avatar
By YorkshireDave
#3699
REDSAW wrote:
October 1st, 2017, 4:41 pm
AH!, yes on the tap connectors it goes down to about 6mm.
the straight connectors bores are all through sized.
i like the idea of using plastic on toilet connections instead so i may try that next time on a twisty fit.

i believe also those hoses split after the stainless braid wire is twisted-brakes a strand then perforates the rubber lining causing a pressure rupture.
Lastly... We have done some research. Strangely we initially thought it would be the braid piercing too. It turns out to be much simpler - when they installed correctly. It's poor quality pipe, basically with walls with air pockets as its cheap. The continual cycling (raising and lowering) of pressure causes the pipes to fail at these weak spots created when the rubber pipes is made.

Many people think a WRAS approved pipe is better quality.THEY ARE NOT. They are the same cheap rubber but its been tested to not contaminate the potable water it's in contact with. WRAS does NOT denote quality of manufacture or performance. They are still made cheaply in their squillions. They are much more expensive to buy because the WRAS approval process costs two arms and a leg and they have to recoup those costs.
By joni os
#3701
The only red herrings here, are people getting incensed about reduction of flow through end connections, when they will happily put a reduced bore iso valve on the same pipework. Plumbing is a Trade not a DIY weekend pastime and any of us fitting a 0.5bar tap would caution if CWS was less than 5 metres above outlet. With water, like gas, pressure drop per unit length is a consideration. Hence 120 metres of MDPE mains supply pipe is recommended to be 50mm bore even though the water meter is 3/4". Esoteric terms are common to all Trades, uses and limitations understood and applied accordingly.
User avatar
By YorkshireDave
#3702
"People"... At least have the courage to say what you mean.

I consider myself my customers champion so take what is installed on their behalf seriously - every bit of it. If that upsets you I apologise but I'll never stop because it's my job to protect them as well as install.

Have a nice day.
User avatar
By REDSAW
#3706
and ceramic tap valves are lesser output size when fully opened than the iso or tap connectors bore- more pressure less flow :?
User avatar
By YorkshireDave
#3710
Truth is they vary considerable - hugely in fact.
Many just manage a cross sectional area equiv of 6mm dia but the good ones do closer to 9mm Whilst that doesn't sound much difference its actually 19 sq mm versus 28 sq mm. A traditional (multi-turn valve inlet (12mm) is 38 sq mm. So, common cartridge = 50% of flow at best, good cartridge = >73%
On a low pressure system (by that I mean up to 0.2 bar) that makes a massive difference to flow rates and usability
By joni os
#3714
No problem Dave. As a general rule when calculating cross section of circle I treat diameter as side of square and deduct 20% from answer. Eg 9 X 9 = 81 less 20% (16.2) equals 64.8 The true answer is slightly less, as above. Useful when checking ventilation etc. only requires calculator in border line cases. This is why your figures shouted error. Don't be hard on your memory, I suspect it was remembering relative perimeters.

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