I'm replacing my pool/spa equipment, and would like to add an additional return line to my spa. The current spa return is 4 jets only. The new lines would bypass the jets. The reason I'd like the new return is to allow me to get enough flow to allow me to run the heater on low speed (Hayward Ecostar.) I'm thinking I'll need the higher speed on the pump to get sufficient gpm through the jets without this bypass, which I would like to avoid during the heating phase. Another benefit is that with reduced flow through the jets they wouldn't be sucking air and cooling the water before I'm ready to use the spa. In heating mode, jets and bypass will be on. In usage mode, the bypass will be off and the pump turned up to active the jets.
There are 2 questions I have:
1) What is the best way to seal the new pipe against the gunite/plaster? I had been thinking of using 3m Marine 5200 injected around the pipe, finishing the spa side with a plaster patch.
2) Drilling the hole. I had planned to used a SDS max hammer drill with 1.5" masonary bit. This will make it through the concrete fine, but I'm concerned about any rebar that I may find in the path.
Any comments and suggestions would be appreciated.