Where does hot water pressure come from in a flat ?

Question

I don't understand our hot-water system. We're in a ground-floor flat. In a cupboard there is a boiler and a hot water tank. There is another cupboard with a couple of header tanks concealed behind a false ceiling (at least one is for the central heating).

In the bathroom the water gushes out of both the (separate) hot and cold taps on the bath and the basin at a fair old rate. So far as I can tell they're at the same presure. Where does this pressure come from ? Would mains pressure feed through the whole hot water system, or is it just coming from the header tanks (which are maybe

1.5-2m above the taps at the most) ?

The reason I ask is we've just had a new kitchen installed and the hot flow out of the (new) mixer tap is completely pathetic (cold is fine). Searching google groups for mixer tap water pressure turns up a whole load of discussion on this group I really wish I'd seen beforehand. Now I'm trying to understand where our hot water pressure comes from to decide what to do about this mess (alternative tap designed for low pressure ? pump ? write off the new sink and tap as an expensive mistake and go back to separate taps ?)

Thanks for any help Tim

Dave Plowman · Accepted Answer

With careful pipework of the correct size, you'll get an adequate flow with a 2 metre head. After, all, you can pour water out of a jug. ;-)

Chances are it's designed for high pressure and has too small a pipe diameter. The pipework to it might also be poorly designed - sharp bends etc. When you run things at mains pressure, these things have less effect on the flow - although they can cause unnecessary noise.

Most of these mixer taps are continental in origin, and they apparently never use a header tank system.

Tim Day · Answer

Oh dear; despite the hot water tank cupboard basically being next to the sink, the pipes trace a pretty zig-zag path across the wall to get to it (several sharp 90 degree bends).

How to tell ? It's a Carron-Phoenix "Opus":

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hot and cold run to separate output nozzles (previous postings suggest continental types tend to mix within the tap). I note they have a similar product

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does actually mention "low pressure systems"; will call them Monday and see if it's likely to be any better.

Thanks for the useful tips Tim

Where does hot water pressure come from in a flat ?

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