Flexebile tap connectors

[DARTHVADER]

Fitting a bathroom suite and for ease of pipework I wish to use 500mm long flexbile tap connectors (the mixer is in the centre of the bath at the back wall)

I require two no. both with 3/4' bsp at one end to to suit the bath mixer, one with 15mm and the other with 22mm at the other end to suit the cold and hot pipework.

My concern is that the flexi connectors I have seen (scewfix) both have a bores of 10mm. I don't think this will be a problem on the cold feed but will this have a an effect on the 22mm hot supply, i.e. will the water feeding the bath be unduly restricted with such a reduction between the sizes. My heating system is combi (28kw I think)

Many thanks,

 

[Softus]

I don't think this will be a problem on the cold feed but will this have a an effect on the 22mm hot supply, i.e. will the water feeding the bath be unduly restricted with such a reduction between the sizes.

Yes.

Also, in time, the hot water will affect the rubber tubing and it will collapse, further restricting flow.

Flexibles are a miserably poor solution that are over-used to solve non-existent problems. If the pipework really is that tricky, then take a look at push-fit fittings, either Hep2o or Speedfit. You can use them with copper pipe, or you can use Hep2o or Speedfit pipe for even more flexibility.

 

[Bahco]

Should be ok on a combi as you have to wait 15 mins to fill the bath anyway.

 

[Softus]

It seems to be a common misconception that flow rate is determined solely by the most restrictive component in the system. This is incorrect.

Every internal surface of every pipe, fitting, and valve, adversely affects flow. The more bottlenecks and rough surfaces you have, the more resistance to flow and the more turbulence there is. Therefore, you can, if you so wish, successfully throttle the desultory output of a combi yet further by using 10mm bore flexibles to connect to the taps.

 

[DARTHVADER]

Thanks for the reply's gentleman.

The first fix pipework is in position now and the tee pieces are aligned to the centres of the holes in the bath for the mixer tap. I think I may just fix overlong plastic pipe fitted to normal tap adaptors and cut to fit at the tee pieces when the bath is in position. So hopefully the flexibility of the plastic pipe should help when I do this. I was just concerned the bulk of the bath would prove tricky in lining the pipes up with the fixed tees. The first fix pipe is a mix of copper and plastic. I have been put off using the flex adaptors.


I used to think they looked crap when they were visible in toilets in whilst on holiday in Spain decades ago.

 

[gas4you]

Why not use 15mm flexis?

 

[DARTHVADER]

Didnt know you could get this sie of bore? the ones in screwfix seem to vary from 10mm to 12.5mm. 15mm would still be a reduction on comapred to 15mm.

 

[Softus]

Er, your typing seems to be going to pot. Have you stopped using The Force?

 

[chrishutt]

10mm bore flexis will be fine, providing you have reasonable access to replace them when they eventually fail. The flow from a combi is so restricted anyway (of necessity) that the resistance of the 10mm bore flexi will have little effect. Even if it does slow the flow a little the water will be hotter so the same amount of heat will be delivered to the bath, which is what matters.

 

[Softus]

Even if it does slow the flow a little the water will be hotter so the same amount of heat will be delivered to the bath, which is what matters.

If the same number of joules is delivered in a longer period of time, then the bath will have cooled more over that period, so I would argue that it does make a difference.

 

[chrishutt]

The boiler will be delivering 28 kW which is then delivered to the bath by the hot water flow. Whether this is delivered by say 11 l/min @ 50°C or 10 l/min @ 53.5°C (assuming incoming mains temp of 15°C) really doesn't make any difference, as long as the maximum allowable DHW temperature isn't exceeded (in which case boiler output will modulate down). In the latter case slightly more cold water will need to be added to achieve the right bathing temperature.

 

[marky9074]

I am glad I have just seen this as I was about to go and buy some flexible tails tomorrow.....

How long do they take to break down? Seems like crap if they break down that easily...

 

[chrishutt]

I'd expect them to last about as long as the taps, perhaps longer, so no particular reason to avoid them.

 

[marky9074]

I don't think I will have any issues with flow as its a pump I am plumbing up from/to...

I think it implied above that heat may warp rubber.....rather than it actually failing?

Mark

 

[Softus]

The boiler will be delivering 28 kW which is then delivered to the bath by the hot water flow. Whether this is delivered by say 11 l/min @ 50°C or 10 l/min @ 55°C really doesn't make any difference

10 l/min would be about 9% slower then 11 l/min. During the extra delivery time, the water in the pipework and the water in the bath will be cooling down, so when the bath is full enough the temperature will be lower. To say that the difference is negligible implies that you've calculated it. I haven't, but I know that it's not a zero difference.