I'm installing some new jets (Hydro-Air Hydro Jet 10-5100 http://www.poolandspa.com/catalog/product004101000496.cfm) in an old fiberglass swim-spa and have a few questions:

1) The jet consists of the Body, Wall Fitting and a Gasket. Is the Gasket supposed to go between the spa and the Wall Fitting (inside/wet side) or between the spa and the Body (outside/dry side)? The Wall Fitting screws into the body, which makes me think the Gasket should go on the outside so it's compressed rather then twisted, but on the other hand, a gasket should normally go on the wet side in order to seal correctly.

2) Regardless which side the Gasket goes on, should a sealant or adhesive be applied to one of both sides of the Gasket itself?

3) I understand I should use silicone sealant, but from what I can tell, most silicone sealants shouldn't be used in underwater situations. I looked at silicone sealants from several manufactures (3M Marine, Dow Corning 732, DAP Auto/Marine, GE Silicone II) and they all said they were not for permanent underwater use. I did find one that seems to be specifically for pools/spas, Boss 802. Are there any other specific brands of silicone sealant good for underwater pool/spa use... in particular attaching a jet?

The gasket goes between the wall fitting, and shell surface. Do not use sealant on the gasket only because it will "walk" as you tighten it, and squeeze out. I personally don't use gaskets on euscution to shell attachments. Spa-FAQ/Plumbing-Jets/Calspa-Gaskets-Deteroriating_4944.html I use GE 50 year clear silicone, and toss the gasket into the neighbor's yard. The seal is not under water. It is between a 1" flange (give or take) and an acrylic shell. So this is me..... Clean front and back of dust, old silicone, etc. Bead the wall fitting (euscution) with silicone, and flare the bead to involve the first few threads of the collar,(wall fitting, euscution) and flange. (Make it pretty now " title="Wink" /> ) Insert wall fitting through hole in the shell, and bead the backside of the shell where the collar is protruding. Flare this bead to involve the collar, and shell. Now screw the jet body into position via the collar until snug. Align the hose positioning (water, and air) Tighten the assembly "Darn Tight" (so it doesn't readily move). Now flare the protruding silicone front, and back to involve the fitting, and shell. (Make it pretty now " title="Wink" /> ) The seal will last about 50 years. If it fails 40 years from now....... call me " title="Smile" />