Thanks guys. I am kind of new to this. First pool. Came with the house. I think the pool has been there since mid 1980's but having only been here about 6 months so I am not sure what is normal. I wasn't sure if it was evaropation since temps are getting in the 90's now here in South Texas or if it was something else. Thanks for the help.

I am glad to know the design is to only run suction in the spa if you operating spa only. If I replace the heater that thas is there but been taking out of the circulation loop, there might reason to only circulate the spa if it is being heated. No heater no need for that.