I have been using Salt in my tub for over a year and really wanted to go to a SWG but there were not any really good choices.. I have an always on circulation pump with 1.5 inch flex pipe and most small SWG were using 3/4 inch barb fitting or a drop in with a cord hanging in the tub...
Cutting into your perfectly good plumbing is not for the faint of heart
Pool Saltwater Chlorine Generator
I found out Controlomatic had the Megachlor that uses 2 inch fittings and is rated from 1000 gallons to 20000 gallons for a pool or spa and has a Chlorine production of 100 grams per day. It is a basic system in that it turns on a set amount of time in a 3 hour period.. I noticed once I received the instruction manual that power level's 1 to 3 are used for spa's and pools under 1000 gallons, so it should do well and is about 6 times over sized
I have a built in GFCI system so I wired the controller in so if I pull the breaker or anything were to happen it would turn off everything and trip the GFCI.. It has a long enough cord that you could plug it into a GFCI plug from your house. another thing, it is always on, so your hot tub would need to have a constant circulation pump like mine. In this picture you can see the 13 amp extension cord cut down to 2 feet and wired directly into my power center, the converter uses 1.8 amps and 100 to 240 volt's and I wired it 120v... so no issues with power. My hot tub uses about 50 amps with all 3 pumps and heater on, I have 60 amp 240 volt power going to it.
I used a 1.5/2 inch jandy valve just in case I needed to replace the cell and did not want to empty the tub.. I plumbed it in after the filter and heater just before it goes back into the tub..