It looks like your pump’s outlet fitting has a maximum tubing (inside) diameter of 1”, so I’d recommend sticking with that!Just a mock again but I’m going to run this 90 to soft plumb the pump, I’m worried about vibration since I can’t clamp the return section to the stand
(Note the grooves after each step in the pump’s barbed outlet fitting; the fitting is designed to be cut along these grooves to omit the unused smaller diameter barbed fitting segment(s) which would otherwise restrict flow!)
— the general consensus for tubing would be to use silicone, 1” inside diameter in your case! (Probably 1/8” wall thickness, thus 1-1/4” outside diameter)… this isn’t cheap, but you’ll only need 12” of it!
to adapt from tubing to rigid PVC pipe:
— you’ll probably want a union, this can go before, or after the pictured elbow…
— a 1” barb X 1” slip, or 1” barb X 1” NPT “adapter fitting” is the part you’re looking for!
— these adapter fittings come in various permutations, you may even be able to find one which combines the pictured elbow into a barbed adapter fitting!
https://www.bulkreefsupply.com/90-elbow-barb-x-spigot-street.html
(Using the above adapter as an example, you could stick the 1” pipe diameter ”spigot” side of this adapter fitting directly into the “socket” of a union, allowing you to quick disconnect/reconnect your return pump, make that 90 degree bend, and adapt to tubing all in two parts!)
