Showers & Pumps

[Ryan]

Hi all,

I've been reading the archive on google with interest on shows and pumps as I'm about to start a bathroom project. I couldn't find a query similar to mine so I'm after a little advice.

I'm going to replace a cold feed shower with a thermostatic mixer shower. I have no problems with mains cold pressure, although I don't know what the exact pressure is. I only need to turn the cold tap on the bath to get a good strong flow of water. The hot is fed from a tank on the landing.

When I had a company out to give me a quote on doing the bathroom for me they said that because the shower head is less than 1 meter below the cold tank a pump would need to be fitted. Now I can't quite see this as the cold pressure is fine but I can understand pumping the hot feed to increase the pressure and therefore making the mix a little more even. Also the cold tank is directly above the hot tank with more than 1 meter between them.

Can anybody give me some advice, is it possible to get a hot only pump? If I was to pump the hot and cold with say a 1.5 bar pump and the cold was already around this pressure would I end up with 3 bar on the cold pipe? Anybody had problems taking the shower feed off the hot and cold pipework to the bath? as the tanks are along the landing and it's not going to be easy to run new pipes.

Sorry if the questions seem silly, I've read too much and I'm now very confused.

Take Care Ryan

[F]

The cold feed to the shower comes from the same tank that feeds the hot water storage cylinder and not directly from the mains. That way they are at pretty much the same pressure.

[Christian McArdle]

Absolutely. I would say that 10 metres was the minimum realistic head for a gravity shower, unless you prefer low pressure dribbly type "soft" showers to jets of water.

A thermostatic pressure balancing shower will operate at the pressure of the LOWEST supply. i.e. it will throttle back the cold to match the hot supply and will just dribble out.

Yes. It is called a single impellor pump. (Look at the Stuart Turner ShowerMate and Monsoon ranges). Ideally, situate it next to the cylinder and have it supply the bath taps also, for rapid filling. Another solution is to use a venturi type shower. These use some of the energy of the high pressure cold supply to suck the low pressure hot water through. Not as effective as a pump, but less noisy and effective enough.

Possibly. However, it would be highly illegal. It is strictly against the law to pump your cold mains supply, as it can reduce the pressure in the supply pipework below ambient, causing any leaks to suck in mud and contaminate the water supply for surrounding properties.

No problem at all, although if you try to run the bath and shower simultaneously, it can cause problems.

Christian.

[Christian McArdle]

It may at your place, but apparently not at the OP's. It appears to have mains cold and gravity hot supplies, which is also common. My last 2 houses came fitted with such systems (but didn't retain them very long...)

Christian.

[Ryan]

Hi F,

So if I understand this correctly when I install the new shower I should alter the pipework coming off the cold tank which currently feeds the electric shower from the mains inlet to the outlet of the tank and not take the cold feed from the pipe work underneath the bath which is coming off the mains.

| |---T--- (Mains Cold) | | L--- (To Electric Shower) | | | |------- (To Hot water tank)

--------

| |----- (Mains Cold) | | | | | |--T--- (To hot water system)

-------- L--- (To shower)

Take Care Ryan

[Ryan]

Hi Christian,

Thanks for the quick reply. From what you have said I wont be pumping the cold supply then only the hot :-)

I look into both F idea of switching the pipework in the loft so both are the same pressure or adding a single pump. When the builder built the house they forgot to add the cold feed to the electric shower and just ran feed from the cold pipe at the mains inlet side of the cold tank to the shower in the loft. I can reuse this and then run the hot up the inside of the wall to the shower from the bath as it's a stud wall. The bath and the shower will never be used at the same time as it's a shower over the bath.

Thanks for the advice I'll look at the possibilities in more detail before making a start.

Take Care Ryan

[F]

Erm, yes.

You take the cold feed for the shower from the same (non-mains) source as the water which is heated in your hot water storage tank.

If you didn't then when you tried to mix the hot and cold to an acceptable temperature the cold water at mains pressure would 'swamp' the hot which would be at a much lower pressure if, as you say, 'the shower head is less than 1 meter below the cold tank'.

From the instructions for installing a Salamander shower pump: 'The cold supplies to the cylinder and to the pump are to be taken from the opposite side of the cold tank to the cold mains inlet.'

and

'NEVER SUPPLY THE PUMP DIRECTLY FROM THE COLD MAINS...' (their caps).

[Christian McArdle]

Personally, I'd prefer to have cold mains and hot pumped. A pressure balancing type shower (in addition to being thermostatic) is essential as the supplies won't be exactly matched for pressure. The advantage is that you can run just cold without the noise and just hot without annoying the pump as twin impellor pumps will attempt to pump hot and cold even if only one side is required.

Christian.