I have a separate bromine spa next to the pool. When I drain it each quarter I've been just using the pool vacuum to suck the spa water out into the pool filter and then back into the pool. I've been doing this for two reasons: I've never been able to get the drain hose in the spa to work and I figured it would save me 500 gallons of water since I regularly need to top off the pool due to evaporation. The pool is 15,000 gallons salt water so I figured adding 500 gallons of bromine sanitized spa water shouldn't hurt anything. I figured any nastiness in the old spa water should be taken care of by the filter and the chlorine in the pool. Is this a valid assumption or could I be causing myself problems in the long run?