[Pete Thompson]

Here’s an idea ;

Most domestic RCDs fitted in consumer units respond at 30 milliseconds.

You could fit, between the plug and the heater,  a slightly more expensive RCD that responds in 10 milliseconds. That way, if you have another incident that causes a trip, it will only trip the 10ms RCD and the rest of the house will be unaffected.

(I have not tried this, it’s just an idea)

[Smudger]

if your tripping an rcd - then you need to find the cause of that problem.

many years ago I use aquarium heaters - just dropped them in through the lid and loose laid it over the top

even at low temperature if its below freezing you still get steam coming off the water in the tank

Darran