What are you connecting the elbow to?
My return pump has threaded ends, so I just used threaded PVC
fittings. If that leaks, you can use some plastic thread tape, but mine are fine as is.
needs to be glued. The regular PVC
cement is fine as long as you let it cure for a few days. <Use the ones for potable water (rather than for sewers) - that is certified to be toxin free after curing.>
If you don't want a permanent connection & don't have threaded ends, you can use barbed fittings & short lengths of vinyl hoses to connect the pipes together. Silicone is safe (use plain, clear, 100% silicone without mildewcide.) but it will not stick to PVC
. <even tho I know better, I tried a quick fix with silicone. It fell apart after just a few weeks.