My experience with Sunbelt has not been all that positive. I know a couple of folks who used to sell them. Notice I say "used to." They stopped selling them because of quality issues and customer service issues.
There are some other mfgs who make swim spas of better quality. My advice, keep looking.
You can also look at Endless Pools. It is now a swim spa, but a small exercise pool. Good quality and better quality swim than you get with a spa. The water flow in the Endless is more spread out, gentle, yet as swift as you need for exercise.
http://www.endlesspools.com
