I require a under sink water heater and my plumber is recommending a
10L 3Kw pressurised water heater but when I have been searching for
one it seems they are either vented or unvented and no mention of
pressurised. It will have a cold water feed from the mains. Can anyone
shed any light on this? Also, will I need special taps?
For the purposes of this discussion, pressurised = unvented.
On most models, you do not require special taps. It's just a mini-megaflo.
Mains CW in, HW stored at pressure, mains pressure HW out.
There are some stranger models around.
These are un-pressurised, yet provide mains-pressure HW, and work like this:
Mains cold comes in, to the tap in the first instance.
The tap does not open directly to the spout, it opens to a return pipe to
The tap then opens the CW supply to the cylinder.
This then forces the stored HW out a seperate pipe to the spout, at mains
In this config, the cylinder is not pressurised, it is open to the spout at
The pressure is only applied when the cold supply is turned on.
These require a special tap ( with a return pipe to the cylinder. )
Sounds like the plumber probably knows what he's doing, and you ought to let
him get on with it.
And I've just had to replace one of mine- only 2.5yrs old but very hard
water area... You can't replace just the element -immersion heater stylee-.
It was an Ultraheat which dont seen to be about any more- the new one is a
Redring. (15l 3kw)
That sounds like it's a unit that just escapes all the really serious
So you may fit it with out a G3 ticket,
plug it into (a FCU on) a 32A ring circuit,
no discharge or vent pipes required (it forces expansion upstream into
In message , Tim..
Umm.. In an effort to avoid this, I installed ours in the *hot* water
The instructions were pretty insistent about expansion issues but I
really could not see any extra safety concerns provided there was ample
feed pipe length and no local shut off valves.