PeterK wrote:
Help needed re a bath hot/cold mixer tap with a hand held shower (switched
by lever at base of outlet).
The instructions state that that water regs require non return valves along
with isolators on the h&c feeds. No problem with that.
The instructions then continue (not under "regs") "to obtain optimal
results......be checked"
a) hot & cold water supplies must be balanced
b) The cold feed should come from the cold water tank and bold not the
mains
c) words to the effect at least 2m head of pressure

Hoping I've supplied all relevant info the question is:
Is the requirement at b) normal - I think its stone age

These dual purpose tap/showers are often given away with a bath suite
in other words value is next to zero.

There are 2 key requirements to make your shower work effectively:

1. balanced pressures on H & C supplies. Dual purpose bath taps cum
shower do not have a pressure/balance regulation valve (at least I've
never seen one that does). Balancing to obatin a reasonable shower
flow rate and a tolerable temperature is simply by adjusting the H & C
taps - a hit & miss affair. Balancing is extra tempremental if the
pressure are out of kilter, thus the recommendation to supply both from
the CW tank..

2 Equipment designed for the supply pressures.

If you have high pressure HW then it might be possible to make your
shower work, but you will need a balancing valve to ensure equal supply
pressure. Normal purpose designed shower fittings incorporate these &
ensure temperature stability even if flow rates change. My guess is
that the manufacturer is obliquely saying that the kit isn't up to a
high pressure supply.

There's a risk of scalding if flow rate and temperature isn't
controlled & maybe the manufacturer is recommending low pressure
operation to limit that risk?

Would I get these requirements from Pegler, Bristan etc. (haven't checked if
they do anything similar)

Sorry can't help there, but I suspect a satisfactory high pressure unit
(if one is available) will not be given away free. One alternative you
could consider is a separate electric shower unit mounted on a wall
above the bath.

HTH