In that case you should leave it alone (imo) and let it do the job it was intended to do. Anything more, you're into a really custom application that will need a lot more attention than what most are capable or willing of giving.

Some day, perhaps this specific application will come up and it will be addressed on a larger aspect that will befit your needs.

Wish the forum could be more specific to your requirements but I'm afraid that it's not.

Thanks and best of luck on it.

Ok, how bout this - what if I get a solar water heater panel, install it next to but physically under the tub, tap it into the two hoses that already go into the tub (using the heat rises principle), and wouldn't that then work - with NO electricity or pump needed? (So it's using the tub as it's storage tank!) I am sure someone makes a thermostat regulator that would keep it from getting too hot...

Is it me or is that freakin genius?