I received my new L4 yesterday and have some questions regarding set up. Do I need to glue the white couplers onto the bottom drains or just push them on?
You only need to bond those on if you are operating the unit remote from a sump (i.e. nothing under it to catch any drips). Otherwise you can just push them on / friction fit. They should fit pretty tight, but if not you can wrap the base extension with teflon tape (2 wraps is all you should need) and that should snug it up.
Do you think I could install a gate valve on the drain instead of the current drain flap valve thing? Would this work and give me easier control. I find it hard to adjust otherwise.
Which version of the flapper valve do you have? Is it the one with the thumbscrew through the pipe, or the one that is integrated into the bubble blocker (with the syringe and fishing line)? But yes, you can install a gate valve instead. What I would recommend is using a reducer so you can go with a 1" gate valve, as the 1.5" is expensive. You could either reduce from 2" to 1", or leave the 2"-to-1.5" one in place, then put in another 1.5" to 1" reducer
