Showers & water pressure

[Andrew Baker]

Wanting to install a new shower, I'm trying to understand water pressures...

My cold water is all direct from the mains (no tank). United utilities say they supply it with at least 7m static pressure. Does this mean it's at least 0.7 Bar, then?

Hot water is fed from a tank. I've a non-combi boiler that's pressurised, but that's just the heating circuit, I think. The hot water tank is in the cellar. I _think_ there's a header tank for it in the loft, though I've not actually heard it filling when the hot water is running (further tests tonight!).

(Is it possible that there's no header tank and the cylinder is fed directly from the mains? I don't think the hot water is pumped in any way - just the CH)

Assuming it is a loft tank, can I estimate the hot water pressure as being the distance from where my new shower head will be to the tank in the loft?

So, with a shower downstairs, and the tank in the loft in a high-ceiling house, that'll be something like 5 or 6 metres, meaning a pressure of about .5 or .6Bar?

Does the fact that the tank will be below the shower head make a difference? Will the 'resistance' of all the pipework make a big different to that 0.5Bar figure?

Or am I completely offside and misunderstanding?

[The Natural Philosopher]

Yes..its possible. The tank if it does run at pressure will have a lot more pipes and safety valves on it.

Yes.

Yes.

No. Some.

No. You are IMHO spot on.

[Christian McArdle]

Yes. That is possible. If you can post a photo, or post what the writing on the side says, we can give a better idea.

Yes.

Yes.

Yes.

However, 0.5 bar is unacceptable for a shower in my opinion, although it is fine for a bath if the flow rate is acceptable. It will also drop dramatically when the flow rises. I would install a pump.

Christian.

[Andrew Baker]

Can I do that, though, given the cold isn't tanked? (I can't pump mains cold & pumps seem to all be dual hot&cold?) Plus, I presume that would mean running a direct feed back to the tank, which is a pain. (Yes - much better in terms of flow etc, but a pain..)

The current (upstairs) shower isn't pumped and is actually quite good..

[Christian McArdle]

You can get single impellor pumps.

If the current upstairs one is good, then the downstairs one is likely to be better. Either you have low expectations, or you do have a mains pressure cylinder!

Christian.

[The Natural Philosopher]

Then you may well be all mains pressure.

I header tank in the roof is just about capable of running a ground floor shower in a 2 storey building..but you need more than the 4-6ft head from a tank in the roof to an upstairs shower..

[Biggles]

Depends on your priorities. You don't need more than that to get a shower you can get clean under, although you do if you want it to be "invigorating". The greater the pressure, the more water and energy you will use.

Biggles

[David Hansen]

On Wed, 05 Jul 2006 01:36:12 +0100 someone who may be Biggles wrote this:-

One will buy energy if one adds a pump. However, one will not buy energy if using a venturi shower.

[Biggles]

Interesting but not relevant to the point I was making. My comments were based on the minimum head required for a gravity shower, not mains or pumped. More head means (potentially) more flow = more energy used for a given temperature.

Venturi showers consume more energy in exactly the same way - more flow = more energy consumed. However, anything which avoids the use of a pump is a good idea in my opinion, as it's one less thing to go wrong, and you will save a bit of energy into the bargain.

Biggles