We've got a bathroom refurb project under way, throwing out the bath (cast iron - that was heavy!) and installing an electric 10kW shower.
Builder is proposing a joint method of connecting the shower so that heated water to the shower head either comes from electric or the existing hot water system (Gas fired S-plan 20yr old Potterton lump).
The logic is that the electric is unnecessary if the gas system has already heated a full tank of hot water, but if that's gone then we'll switch over to electric heating.
I'm shaking my head negatively as it sounds a bit complicated, and would much rather it was just kept electric, but SWMBO and the builder is a bit keen on this - so I'm currently being overruled.
Are there any water regulations precautions peculiar with this kind of switched arrangement. The DHW system heats tanked water, the electric will be running from mains pressure. Lots of pressure from both, we don't need pumps.