Some hints and tips on Electric show pumps
Always ensure that the power shower pump has its OWN dedicated hot and cold feed pipes, to the pump inlet pipes. This ensures that the pump pressure remains as constant as possible, so that the temperature remains at the desired setting.
Choose the siting of the pump carefully, and consider where the cold feed pipe comes in to the pump area, as well as the hot feed, and the outlet pipes to the shower cubicle. Also consider the mains power, and if you are competent to fit a 13 amp socket in the area, that is often the most convenient. That will mean that you can fit the plug-in RCD unit of your choice, and anytime the pump needs maintenance, it will be a simple matter of unplugging it form the supply, rather than mess with wiring to isolate it. The airing-cupboard is often the best choice
Some high power pump installation instructions recommend installing the pump on a concrete slab for noise reduction, but a breeze-block (sealed and painted) will often suffice, and in any event, most pumps will have rubber feet. It is also a good idea to have a plastic tray between the pump and the mounting block or shelf, as pump seals can wear and leak a bit over time. Also, some pumps have a mesh filter that needs checking from time to time, and the bit of water that comes out when removing this will go on your tray, not on the carpet or floorboards. I have a thick wooden shelf for mine, but it is fairly quiet.
The cold feed pipe from the cold tank in the loft MUST be lagged, as should ANY pipes going up into the loft, across to your bathroom shower.
CONNECTORS:If you need to fit a tank connector to the cold tank (e.g. SCREWFIX number D18109), obviously the tank needs to be drained. If you plan the time when you want to fit this, so that you waste the minimum of water, turn the cold feed off to the tank for a couple of days prior to your work. This way the water will actually be used, rather than be wasted. It may be more than 2 days, depending on your tank capacity. When you have fitted your tank connector (drill an appropriate sized hole a similar height from the bottom as the other take-off points, usually a couple of inches), fit a short piece of 15mm pipe to that, and fit a full-bore ball-valve (e.g. SCREWFIX D11085) so that you can leave this in the off position, then restore your cold water to the rest of the house, whilst continuing with your other pipe fitting work.
FLANGES: There are several types of flange that will connect the hot supply pipe to the hot tank. There is the SURREY FLANGE (also known as a DANZEY FLANGE), a YORK FLANGE, and an ESSEX FLANGE. The first 2 types go on the TOP of the hot tank, replacing the existing connection. The ESSEX flange goes on the side of the tank, a couple of inches from the top seam. The disadvantage of that is it needs more water drained off, and a fairly accurate hole drilled in the tank. The component parts are also fiddly to install, and there is as risk of dropping the parts into the tank, off the temporary holding wire. The top fitting flanges (SURREY/YORK) have their own 15mm or 22mm take-off point for the hot fed pipe to connect to. These will also be at the highest point, so allowing the full extent of the hot water to be used form the top of the tank (hot water rises to the top), and there is no disturbance to the tank itself. See the next page for information links, and links to an excellent write-up and graphics on FLANGES, and fitting POWER SHOWER PUMPS, from http://www.watermillshowers.co.uk
DIFFERENCES BETWEEN FLANGES: Note that SURREY FLANGES fit on to a hot tank with a 1 inch FEMALE fitting, and the YORK FLANGES go on to a MALE fitting.
If you are fitting a more powerful pump (2.0 BAR or greater), and are thinking of supplying 2 showers to 2 bathrooms, then fit 22mm flanges and fittings. See the very useful information at: http://www.watermillshowers.co.uk/pages/advice.htm
Although gate valves are mentioned, to isolate the inlet pipe feeds to your pump, I favour the full-flow ball valve, as they are not prone to scaling-up, and are a complete seal, with no drips.You can get both 15mm and 22mm full-flow lever ball valves from SCREWFIX (D11085, and D18343 are 15mm and 22mm with Blue lever, and D21289, and D45277 are the 15mm and 22mm with RED levers.)