Installing a mixer shower

[Andybig10]

Hi. Im about to buy a mixer shower.
my cold water pressure on my existing bath/shower mixer is ok but the hot is a little slow.
I would like to install a pump also to give it a boost.
My questions are:

1) should i tee off my hot and cold water supply serving my bath taps, run an insulated 15mm pipe (copper or plastic??) up a chased out cavity in the wall to feed the new mixer valve above, or would you recommend running a seperate pipe downwards from the cold water storage tank in the loft directly above too feed the cold side of the mixer valve, and a seperate hot feed from the airing cupboard pipework six feet away. the existing pipework serving the toilet cistern,sink and bath runs in a cavity from the airing cupboard?

2) If i wanted a install a pump would it be better to house it in the airing cupboard and install it in line on a new run of hot and cold pipework before it reaches the mixer valve.

Please forgive me if my explanation is ****e or I have answered my own questions. I would appreciate some advice..Ta!

 

[BenStiller]

For starters i think your getting confused with a mixer shower and a power shower....mixer mixes your existing pressurised water feeds, and a power shower adds a pump to your existing feeds (providing they are not pressurised.

Have a read of this webpage

http://www.plumbworld.co.uk/53-0000

 

[Andybig10]

Yes V. confused now. So what your saying is, I dont need an added pump if im taking my feeds from an already pressurised feed. The reson i asked is that my hot water pressure on my existing bath/shower mixer is dead slow and needs a boost. The cold water feed from the tank in the li ft directly above would not be pressurised would it??
How else can i boost the hot water supply.
I appreciate your help. cheers

 

[Gasman1015]

A mixer shower valve can be used from gravity or pressurised feeds, if gravity then you can boost the supplies using a seperate pump, a power shower uses your gravity feeds and contains a small internal pump.

 

[stanrog]

Just a thought:-

Re lack of hot water pressure, possible solutions in 1 of your question would not solve low pressure from tap thus is low pressure from the shower only or also when you run the bath tap. If just shower, fault would seem to be within your existing mixer.
If pressure is low on both but is okay from your sink and if the feed to your sink is taken before that to your bath, possibility of blockage/air lock/kink in pipe work from after sink feed to bath.

 

[Softus]

Yes V. confused now. So what your saying is, I dont need an added pump if im taking my feeds from an already pressurised feed. The reson i asked is that my hot water pressure on my existing bath/shower mixer is dead slow and needs a boost. The cold water feed from the tank in the li ft directly above would not be pressurised would it??
How else can i boost the hot water supply.
I appreciate your help. cheers

The only pump you can put on a cold mains feed won't deliver enough to wash a mouse, but I don't think you're proposing that anyway.

Without getting too complicated you have two options:
1. Shower combining a pump and thermostat;
2. Shower containing thermostatic valve with a remote pump.

Neither of these is cheap, but option 1 will be cheaper and marginally less work. However, for any pump the manufacturer will recommend that you take the cold feed to the shower straight from the cold storage cistern, and a hot feed from a Surrey flange on the cylinder. There are ways to avoid the latter, but if you do it all correctly you won't regret it.