22mm bath tap pipes


Postby Karen777 » Tue Sep 02, 2008 8:37 pm

We are replacing a bath. The existing copper water pipes are 22mm. We were expecting the pipes to be 15mm. We now intend to reduce the 22mm to 15mm pipes and then to taps - is this okay? Or are bath taps supposed to be fed by 22mm pipes?
Apologies if this is a daft question.
:?
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Postby bobplum » Wed Sep 03, 2008 9:37 am

morning
depends on the taps and the system
are the taps for high pressure or low
the system you have is it a combi or gravity system
lets assume you have a gravity system,ie a hot water tank and a cold water tank in the loft and the taps you have bought are for high pressure system chances are you will be disapointed with the preformance of the taps
can you get come back with more info
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Postby busy » Wed Sep 03, 2008 1:08 pm

Baths are fed by 22mm pipes to provide the volume of water required, you should leave these and connect the new bath taps to them. You will find your basin is fed by 15 mm pipes.
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Postby chris_on_tour2002 » Wed Sep 03, 2008 6:40 pm

in almost all cases bath taps are 22mm. as 'busy' says it is to provide volume so you don't wait an age for you bath to fill. you'll probably find that the taps you buy will be three quarter inch as well. you can get half inch bath taps but i'd stick with the 22mm pipework.
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Postby htg engineer » Wed Sep 03, 2008 8:22 pm

If the water is supplied by a tank/cylinder then you need to leave the 22mm pipes in place. If you have a combi boiler, best to get rid off ALL 22mm and use 15mm.

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Postby Karen777 » Thu Sep 04, 2008 7:40 am

Hello
Thank you for all of your replies.
At the moment I have a gas boiler (Potterton) and a hot and a cold water tank. The water pressure for the old 22mm pipes bath taps was grand. I hear what you say about losing pressure when 15mm pipes is used for a gravity fed system.

At some point in the future I was thinking about changing over the boiler as it looks really old and I would rather change it before it conks out. However, don't know when that will be so we might keep the 22mm bath tap connection and then change over to 15mm whenever we fit a combi.

Please advise if there is anything else that i am missing...
Thankyou
Karen
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Postby Newps » Thu Sep 04, 2008 8:27 am

Message to htg engineer,
Whats the reason for switching to 15mm pipes for the bath if you have a combi boiler?

Will it give better pressure?

Reason for question is we have cold water fed from cold water tank into bathroom and installed a combi lasy year so hot water is also now fed up through same pipes (22mm) to bath taps which is also a shower mixer tap.

The shower is always very hot and it appears that the hot water has more pressure than the cold because if we open basin cold tap after a shower the water in the is hot for a few seconds?

Thanks
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Postby chris_on_tour2002 » Thu Sep 04, 2008 8:57 am

[quote]"If you have a combi boiler, best to get rid off ALL 22mm and use 15mm." [/quote]

hi htg,

do you mean on the domestic supply only? you wouldn't want to change the F&R pipes to 15mm if its currently in 22mm?

chris
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Postby htg engineer » Thu Sep 04, 2008 3:49 pm

All I'm talking about here is the DHW pipework, not the central heating flow and return.

Flow rate and pressure are different factors, you can have a good flow rate, but with poor pressure, and good pressure but poor flow rate.

1 metre of 22mm pipe holds 0.32 litres of water.
1 metre of 15mm pipe holds 0.145 litres.
This cannot be increased, so 22mm pipe holds more than twice as much water as 15mm.

The combi boiler mains cold water will be fed by a 15mm pipe, so connecting to a 22mm pipe on the outlet, firstly it will take longer for all the cold water lying in the pipe to clear so running off litres of cold water before getting warm water - then eventually hot water. And you will be losing of heat.

Abit of an exaggeration, if you had a 10cm straw connected to a tap and 10cm of hose pipe, how long would it take to fill the hose with hot water ? and if flowing through - the hose would never actually fill with water.
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