I used a barb on mine. I don't know how the glue will react with spa flex. Actually since the spa flex won't exactly fit in there because of the shape, I wouldn't do it. Home depot and loses both carry barbs that ought to fit in your reducer. If not they will have an adaptor. If you can't find it pm me with what you need and I will dig through our irrigation stuff for you. Another place to check out that we get alot of stuff from is John Deere Landscapes off ih35.