Just picked up a used hot tub for my brother and law. It had a heating problem (bad pressure switch). When changing this I noticed the vertical heater unit had alot of white scale in it. I removed the top of the heater and it is full of scale.
Question is, is it safe to use CLR or similar on the heater element?
Or is there something better to remove this?

ranman

Best bet is to replace it. If you can extract the element it's pretty cheap to replace.

http://spapartsnet.com/Electric-Heaters-Parts

I soaked it in CLR last night for 3-4 hours and came out perfectly clean.
So this does work and does not seem to have hurt element.