Gate valve output before or after UV and other manifold questions

[RKeenan]

So did a dry run with soft tubing to check UV fittings and Red sea DIY hard pipe adapters for leaks and all good. Ready to put manifold together but still have a couple of questions. Running a Varios pump to Aqua 25 UV and wanna put an extra output inline with gate valves in line and on the return line. Question 1 is better to have optional future use t fitting/gate valve before or after UV or does it really matter. One thing I thought was PITA in my initial testing was every time shut off pump and siphon's back into sump always have to readjust the downpipe (upgraded gate) valve to get to correct (quiet) overflow box level. Thought about putting a check valve to stop that but know they can be bothersome so thought would ask opinions? Also since the UV is mounted horizonal (I know not ideal but not many options there) I am constantly having shake it around to get air bubbles out after pump restart so thought about Wye valve right after pump. Any thoughts greatly appreciated.

 

[Mastiffsrule]

Evening,

I have the Uv horizontal as well. If I remember correctly that was the recommendation by AquaUv. I plumbed my with a true union just before the gate, then a barn fitting on the other end of the gate to my UV. Then the output to the return.

I am not familiar with your tank. Can you have a siphon break somewhere before the tank drains that far down to stop water from draining the UV housing?

 

[Reeflux]

The Wycheck George Fisher Angle seat check valve can be installed in the horizontal position. So long as the Angle is facing up.

I'm going to be tight for space as well with my UV. It's being run horizontally, on its own return....... ill probobly go........Pump, union, gate, uv, wycheck valve, union, tank..... Maybe