Should a new spa share water with pool?

[waterbear]

only in losing the heat in the spa, water from evaporation from the waterfall and reduced circulation in the pool from the return jets being off. You can adjust the return valve so that when it is in the pool position it just trickles water into the spa to keep a fresh supply of water in the spa but still keeping a good supply of water going to the pool returns (automatic actuators like the Goldline allow this by adjusting the cams in the actuator). This might be the best of both worlds if you don't care about the heat loss in the spa. That way when you put it in spillover position you will get fulll spillover operation and in pool position you will get some spillover but still good water circuation in the pool. It takes a bit of tweaking the postion of the return valve to get it just right. I elected for total shutoff of the spillover in pool position since I use solar covers on both the pool and spa and that makes it a bit difficult to leave the spillover running all the time!

[MarkC]

I'm assuming your pool is already in. You should get some prices on what a gunite spa will cost. When I had my pool constructed my builder told me $4,000 to add the spa while the pool was built. The price adding it after was 3 times as much as he has to bring out all the same subcontractors just to build a little spa. Do you plan to close your pool during the winter? If you do a free standing spa may be a better idea as you can leave that running during the winter. I wonder if you can get a freestanding spa that could be set in the ground? Access to the mechanicals may be an issue for this approach.