In message , Tony Bryer
writes
On Fri, 23 Mar 2007 15:25:13 -0000 Donwill wrote :
Polite suggestion---- These things can be DANGEROUS and can EXPLODE, If you
don't know how to proceed, then DON'T, get someone in who is familiar with
the installation of electric under-sink heaters.
They are meant to be installed with an open vent tap which are very
expensive, the water expands when heated and drips out of the open vent
tap, the outlet is always open and the tap controls the inlet side of the
heater, I recently purchased a tap for my heater which cost me approx £90.

I will agree about the potential for danger but in many cases you no longer
need an open vented tap. The requirement is either for an expansion vessel or
for a suitable length of pipe between the heater and incoming main. You also
need a safety valve.

I have something similar but not Ariston. I suspect these are imports
from a country with rather different rules on plumbing installation.

I fed the output from the over-pressure relief valve to the *washing
m/c* input on the sink waste trap. Overflow outlets are meant to be
visible to avoid waste!

The other issue is that of expansion. My instructions, translated from
whatever, required a minimum length of connecting pipe on the input
side.

The third issue, which I probably should not mention:-) is the
requirement to connect to the cold feed. The whole purpose in my
installation was to overcome a problem with overlong piping from the hot
water cistern. This is a hard water area and it seemed really stupid to
not use pre-heated softened water.

regards


--
Tim Lamb