On 02 Apr 2021 17:27:56 +0100 (BST), Theo
wrote:

T i m wrote:
Yeah. I think the problem with using hot for that, given a DW can only
spray not immerse etc is that if it sprayed hot then stopped, anything
not removed might be left to bake on to some degree?

That's what our inherited one does ('Diplomat'). It's pants. You put in
greasy oven trays or oven dishes and it bakes on the grease for you.

LOL!

The problem with hot fill on dishwashers is that egg proteins coagulate with
hot water, whereas filling cold before heating dilutes them enough to
prevent coagulation.

Ah, clever.

I've never checked but do they dry the plates by running the heater
element in air or by spraying everything with very hot water then
leaving that to evaporate off?

I think they spray hot water around. This is why crockery (which has a high
thermal mass) dries better than plastic (which doesn't).

Check. I wasn't sure if the level of steam was from sprayed hot water
or water evaporating off the stuff.

I think the 'point' of an inline heater of some sort for us (storage
or instant) is to reduce the time to hand washing temperature water,
and reduce water wastage as much as possible.

So either solution should work (on a cold feed) with the instant
likely to be both cheaper and easier to fit (mostly space but also
power and hot / cold water the other side of the wall).

We have an instant on a sink that's been retrofitted away from the main
plumbing. The leg would be maybe 8m from the tank, which is a bit much
for drawing from cold, especially if you're just washing your hands.

Noted.

OTOH
the instant is on a 13A plug and isn't much good at heating either - it
takes a long time to get going

Time roughly? More than 5-6 seconds?

and doesn't give much more than a trickle.

So we are talking more of a host outlet than a spray here?

Also, it seems to be beyond plumbers to insulate their internal pipes to
avoid cold legs. That's no help on taps you might use once a day, but would
seem to be a no-brainer for the bathroom/kitchen tap that get used regularly.

That's what I thought but my builder suggested to leave them bare so
they would benefit form any surrounding heat, and hopefully stopping
them freezing in the winter if the place was left unheated? Only for
those pipes running though the downstairs ceilings obviously.

If you were to lag those pipes efficiently I wonder if you could keep
the whole pip hot (or warm at least) with a thermostatic heater wire
and if it would be any less economical than buying / fitting / running
a real supplementary water heater?

If all we are doing is buying some time by removing the cold leg, what
if we removed the 'cold' part of the leg? ;-)

If you couldn't insulate the whole pipe properly there could be the
chance of gravity / convection circulation within the pipe itself,
spreading the heat to any sections without good insulation?

Or if I get rid of the tumble dryer and re-position the multipoint
heater in the utility area, then the pipe runs to both hand basin,
bath and sink would only be a couple of meters. ;-)

What are the rules re a balanced flue terminal being over the pavement
(EOT)? (it's there atm but 20' above the pavement, not 6'). ;-)

Cheers, T i m