To Pump or Not to Pump?? That is the question

[stuart2979]

I am installing a thermostatic mixer shower in my bathroom. I was going to install a pump in the airing cupboard and then install all the usual piping as this is a gravity fed system. HOWEVER her indoors with all here wisdom has decided she would like to have a combi boiler installed in the summer hence the wasted money on extra piping and a shower pump that will not be any use when the combi boiler is fitted. WHere is the best place to tee off from the hot and cold supplies to go direct to the shower mixer. For instance could I go from the pipes that supply the bath (22mm for the hot and 15mm for the cold) . All help gratefully apreciated.

 

[felix]

Bad plan. That bath cold tap might be mains pressure for a start. Even if it's from the cold tank, would YOU like to be the one in the shower when somebody turns on the bath tap and pinches all your cold water? It's quite bad enough when somebody turns on the hot tap in the kitchen and your shower runs cold.

The ideal place to connect the cold side of the mixer is straight into the cold tank. This will give you constant cold pressure no matter how many other taps are on - unless the tank runs dry of course!

I'm tempted to say that the best place to get your hot supply is from a dedicated hot cylinder. With a basic mixer, this is the only foolproof way to avoid unexpected cold showers - apart from locking everybody else out of the house. Fortunately you have a thermostat in your mixer so you can tolerate drops in hot water pressure.

Take the hot supply from a pipe that has little flow in it. The vent pipe is usually a good choice. It's big, it comes straight off the top of the cylinder and the water in it isn't going anywhere else. Naturally you must connect at a point which has water in it, preferably below the bottom of the cold tank.

If you don't fancy cutting into the side of your tank for your cold supply, you can tee into the hot cylinder's cold feed. You don't have to worry about varying pressure drop between the tank and your junction because the same drop appears in the hot supply. Connect as high up as you can and MOST DEFINITELY higher than the top of the hot cylinder.

Don't forget to put isolating valves in your pipes so that you can fix the shower in future without draining the cold tank.

 

[stuart2979]

cheers for that. can I use plastic piping for this with pushfit connectors instead of copper??

 

[breezer]

useless but true: you can also get copper pushfit

 

[Bahco]

Good advice from Felix for your present set up but I hope you are aware that you will have to redo your piping once the combi is installed.

The cold will have to be off the main and the hot taken direct off the combi

 

[felix]

Quite true BAHCO. I can't see an ideal solution short of doing without a shower until the combi arrives. Stuart2979, the only thing I can suggest is that you plan your pipe runs to make the eventual changeover as easy as possible. Compression joints - or those push fits - are easier to alter than Yorkshire fittings when the time comes.

NB: Please DON'T put in a redundant link from the rising main to the shower cold supply. Think what would happen if somebody opened the valve by mistake.

 

[kevplumb]

IDEAL soloution howay felix

 

[stuart2979]

Thanks guys. I will take a feed off the cold tank in th attic and the hot from the pipe out of the top of the cylinder. It is not far from there to the shower so not a lot of money wasted on pipes and fittings. Is there and flow advantage to running the pies under the floor and up to the mixer rather than throught the loft and down to the mixer??