UTH size for a tub

Does anybody have a chart or something specifying what size uth works best with certain size tubs?

thanks

I use the 20 gallon tank size on 41qt tubs as emergency or cleaning time holding backups.....BUT.....I always use a dimmer or thermostat on them because they will overheat not maybe....they will;) The real small ones for ten gallons I have temp gunned at 104 degrees:O So just make sure you use a control on them and you should be able to find the right size and temp:gj:

i have never had one over heat...
but it may be because i have them on a ceramic tile, and a 12 hour on 12 hour off timer...?

idk, but yeah, use a thermostat...