We're considering a small under-sink unvented water heater for our kitchen as it's so far from the hot water tank it takes several minutes (and lots of wasted water) for hot water to reach it after the tap is turned on.
It's only for the odd non-dishwasher bit of washing up and for cleaning surfaces etc. so we think a Redring MS6, 1.5kW 6 litre one should be quite sufficient.
Our water pressure is within the MS6 specification so we don't need a pressure reducing valve.
However we will need an expansion vessel as the cold tap for the sink is (unsurprisingly) adjacent to the hot tap (well, it's a mixer). The specified expansion vessel:-
costs *more* than the water heater! That's really ridiculous.
I'm thinking of simply adding a loop of copper pipe to give the required 1.7 metre length that's required to avoid the need for an expansion vessel. 1.7 metres of copper pipe will cost a whole lot less than £75!
Is this a sensible idea?