Toby wrote:

"Michael Kilpatrick" wrote in
message ...

Does anybody know of a particular model of "undersink" type low-power
electric water heater which is designed for a low-pressure water
system with header tank, not mains pressure?

I seem to be struggling to see anything online which clearly states
that it is (a) for water systems at header-tank pressure only and (b)
does *not* have hot water storage but only provide instantaneously
heated water.

Any particular model names much appreciated.

Michael


You just need to look at the minimum pressure requirement of the heaters
and then you will see what will work...

Indeed...but a lot of the listings online don't give full information.
Can't see the wood for the trees.

There will be a fairly low head. It's a bungalow.

I'll explain - we insist on having a *proper* bidet in our new en-suite.
Not those stupid over-rim fill units but a proper ascending spray bidet.
There used to be one in the old main bathroom fed from the vented hot
water cylinder sytem and the cold water tank. That gave a perfectly
adequate head for the spray.

Unfortunately the ridiculously overbearing regulations make it very
difficult to fit a proper bidet these days - and our new heating/water
system features an unvented hot water cylinder which of course is
coupled directly to the mains.

In order to fit a proper bidet we would need to install a small header
tank in order to have an air-gap isolated water supply, and in order to
get hot water for the bidet therefore the only practical option is to
have a small electric heater fed from that header tank. A storage heater
would be a waste of energy given the low frequency of use. The amount of
hot water use is minimal, so something that is a 5kW instant heater is
all that is required.

Seems difficult to find something as simple as this!

Michael