Need advice on correct adhesive

[Billionj]

I am trying to waterproof a threaded pvc pipe through a 3/4" hole submerged 3 below the waterline. Between my 2 pvc nuts on either side I have a 1/2 inch plywood, and on the water side I have a poly sheet. On the water side it goes, threaded pvc nut, large pvc fender washer, 10 mil poly sheet, ply, then on the other side I have a pvc nut threaded onto the threaded pvc pipe. The seal needs to be between the pvc nut and pvc washer, and also between the pvc washer and the poly sheeting (both on the water side). The question is, what adhesive/sealant should I use? The other requirement is this project is a portable water cache and the adhesive should not affect the potability. If that is not quite clear, please ask.
Thank you very much.

 

[bricechivalier]

For the conditions You have described the waterproof wrapping tapes seem to be perfect option.

[link

http://www.alamanda-polymers.com/co...lycol-block-polyl-glutamic-acid-sodium-salt-0

]details about this[/url]