If everything minus the heater is 110 volts, why cant the tub be rewired for either 110 or 220? I have made a quick look on my tub, and as far as I can see the pump, light, box, everything except the heater is 110 volts in the access panel of my calspa (mid 80's) so why cant another electrical system be added? I own an RV and everything is designed for dual voltage. It can run on 12vdc, or 110vac. So If everything is 110 volts, logic would seem that all I would have to do was change the heater element, and hook up the 110vac line and my tub should be running fine right?
Any help here would be great! thanks!!!

I have found out that converting a 220 tub to 110 is very simple. Omitting one wire at the plug and the first relay. and changing out the heater element (40 bucks) and your styling. The relays in the tub are all 110 or 125 volt, so they will only transferr the power that is used. Inthis case the only power they need is 110, minus the prior 220 volt heater which is now 110 the only thing in the whole tub that was 220 was the heater. Everything else in the tub was 110 volts. Tub works great. So depending on your conditions you can convert from 110 to 220 and back depending on what you have available near you tub.
You just have to keep a spare heater element for your application. Well at least with an old calspas tub.