22mm hot 15mm cold

[cobblerz]

I am replacing my bathromm suite, and notice that the hot supply is 22mm and the cold supply is 15mm. the hot is supplied from a cylinder and the cold is direct fed from the mains. is there a specific reason for this difference in the diameters of pipework?

[meldrew's_mate]

Cold will be at a higher pressure than the hot, so can flow higher rates through the same size of pipe. Consequently 15mm pipework will probably be adequate for the cold, though you will have to add a non-return valve to the cold pipe if you use mixer taps anywhere in the bathroom (to prevent backflow)

[chrishutt]

The mains cold is supplied at a much higher pressure than the tank fed hot, so it can overcome greater resistance from the pipework. the flow rate from the cold tap will probably be much better than from the hot, despite the smaller pipe. Mixing hot and cold at very different pressures (in a shower for example) can be problematical and should be avoided.

__________________
Let's face FAQs.

[Water Systems]

chrishutt wrote:

The mains cold is supplied at a much higher pressure than the tank fed hot, so it can overcome greater resistance from the pipework. the flow rate from the cold tap will probably be much better than from the hot, despite the smaller pipe. Mixing hot and cold at very different pressures (in a shower for example) can be problematical and should be avoided.

You can use a Trevi Boost venturi shower which works well as long as it fitted within the makers parametres. You can also put an in-line Grunfoss booster pump on the hot and have a pressure equaliser on the hot and cold before the mixer. This will ensure the cold is dropped to the same pressure level as the hot.

[fitz1]

if its for shower its easier and cheaper to fit a tank fed cold from storage tank.if tank is big enough.

[cobblerz]

Cheers the information, your help is greatly appreciated

[Bamber gaspipe]

cobblerz wrote:

I am replacing my bathromm suite, and notice that the hot supply is 22mm and the cold supply is 15mm. the hot is supplied from a cylinder and the cold is direct fed from the mains. is there a specific reason for this difference in the diameters of pipework?

The simple answer, if you are unsure, is to leave all pipework well alone & just tie in to it.You do not need to know the why`s & wherefore`s. Just re-install your bathroom exactly how it was originally.

[Water Systems]

fitz1 wrote:

if its for shower its easier and cheaper to fit a tank fed cold from storage tank.if tank is big enough.

Then you have put in one of those awful twin impellar pumps that whine and shake and take up space. The Grundfos Booster looks like any other Grundfos pump. Cheap too at around £80.

[Water Systems]

Bamber gaspipe wrote:

cobblerz wrote: I am replacing my bathromm suite, and notice that the hot supply is 22mm and the cold supply is 15mm. the hot is supplied from a cylinder and the cold is direct fed from the mains. is there a specific reason for this difference in the diameters of pipework? The simple answer, if you are unsure, is to leave all pipework well alone & just tie in to it.You do not need to know the why`s & wherefore`s. Just re-install your bathroom exactly how it was originally.

Strong helpful advice indeed. My God.

[Softus]

Water Systems wrote:

My God.

Yes my son?

[cobblerz]

is the grundfos booster, from the water tank or is it just used as an inline booster for the shower?
[/quote]

[Water Systems]

cobblerz wrote:

is the grundfos booster, from the water tank or is it just used as an inline booster for the shower?

The Grundfos is on the hot from the cylinder. Best have it on the shower only if all the other taps are fine.
The cold is from the mains.
The pressure equalizer makes sure the highest pressure is dropped to the lower pressure equalising the hot and cold.

Many mixers already have these inside the mixer, if not it is a extra item costing around £20.

The Grundfos booster has its own flow switch:
http://www.grundfos.co.uk/web/homeuk.nsf/MenuDocumentsDesc/82F2C3EFDD43BFA180256E0F00563537?OpenDocument

Works well.

[cobblerz]

Cool, cheers for that!

How will i know if the mixer has the equalizer, it is a Bristan Artisan, which has thermostatic control, but that is all I can tell at the moment

[Water Systems]

cobblerz wrote:

Cool, cheers for that! How will i know if the mixer has the equalizer, it is a Bristan Artisan, which has thermostatic control, but that is all I can tell at the moment

Ring the makers. There is so many different types of mixers and the ranges change by the week.

[cobblerz]

OK will do