Hi what would be the best glue to use to glue plastic tubing to small
plastic pots that would be full of water. I was going to use silicone
sealant but it says not to use in permanently damp conditions. The joint
would in water all the time. This is to make a watering system for a
greenhouse.

I think Ed Sirrett mentioned a couple of adhesives the other day
(another thread has me asking where to get one of them) - FT101 and
CT1 - both sound like they'd work great, but it might depend on what
type of plastic it is.

http://www.ctecuk.co.uk has videos of CT1 showing it sealing joints in
running water !