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Yes, the TX will run fine on a 15 amp outlet. But just like a 20A tub, the TX should be the only item on that 15A circuit. How do you know if that outlet runs other items in your home? Simple: plug in something which makes noise. I use a vacuum because there is almost always one around, but a stereo, blow-drier or something similar works fine. Turn it on, and then go to the main house panel. The breakers should be labeled (by law) but they may not be. If not - Shut off breakers one at a time, skipping double breakers and the main breaker. Once you determine which breaker feeds the outdoor outlet, (silences the vac), leave it off. Then transfer the vac around the house, searching for other outlets which are now off. START in the bathrooms, because it is very common for houses to have one GFI in a bathroom (required by code) which then daisy-chains to other bathrooms and then outdoors. That is a problem if people in your home use a blow-drier or other high-amperage appliances in those bathrooms. In my house the patio outlet is daisy chained off two of our bathrooms, and one of those outlets is a favorite place for our maid to plug in a vacuum cleaner and/or floor cleaner to do the floors in that part of the house - that would be a problem if we had a 110v spa.
Okay, I did the test and the circuit the outdoor outlet is on also includes two outlets in my bathrooms and an outlet in my garage. Unfortunately I have a treadmill, TV, and Apple TV plugged into that outlet in the garage, so I guess I would need a dedicated line run for the hot tub.I saw a post by you about the TX but it was a while back I think. You said that the TX, if run at 115v/20a, would be able to have both the heater and jets run simultaneously without the need of a 220 line. Is this still true?