Our shower tripped the electric on Saturday morning, it still warms the water but it’s not hot. There’s a ‘power’ selector which we usually set to low in summer an high in winter to account for the ambient temp of the water tank in the loft, it seems like the high setting doesn’t work.

The high setting is a switch to a second element so it could either be the switch or the element.

Before I bury myself in manuals and DIY guides, any plumbers want to stand up and say it’s “definitely xyz”?

The second heating element may have burnt out. If you open up the shower there may visible blackening where the magic smoke escaped. Run a continuity test on the elements. Check around for any signs of arching.

Good plan. Is this the same magic smoke as in the Lucas electrics in the Midget, I think I’ve some spare in the garrage.

How simple is it to swap one shower for another, looking at the spares list a new heating drum costs as much as a new cheap shower unit. I guessing if it is the element then it’s our water hardnes’ “epic” rateing. Involving actual plumbing, or will there just be a length of flexy hoze pokeing through the wall behind it?

I have a mate who designs showers – as The Brick says, it is almost certainly the element. He says they are designed with little performance margin to keep costs down and therefore have a finite (and variable) life. The elements are combined into the weater heater and this item represents a signifcant cost as part of the overall shower, so not surprised its boderline uneconomic to replace. He picks new ones up for me off the production line when ours burn out 😉