Changing return pipe diameter along the run

[Morpheosz]

I have a new 75 gallon setup and my sump is plumbed from my basement. The tank came with a 3/4" return plumbed into it so changing that end is not really feasible. I have 2 EFlux 6010's for redundancy. Each one can return water to the tank on its own at a fairly low rate and together they do a passable, but slow job of turning over the tank. I feel like I should try to get a bit more out of them as the tank is new and as things age I fear the turnover won't be great. I plumbed them with 3/4" hard PVC from the basement. I found a 45 degree Y to combine their flow (as the tank has only one return) and used a couple of 45s to jog the pipe over. I also have check valves on each one so if one dies they other can continue to feed the tank. I assume those check valves add quite a bit of head pressure.

My question is about pipe diameter. Knowing that I have to reduce to 3/4" at the tank given the way the tank is plumbed, would I see a noticeable improvement if I replaced the rest with 1" PVC or does it all revert to the lowest common denominator, the 3/4" in the tank? I realize I'd have the benefit of less smaller pipe to restrict with gunk over time, but not sure if that's a game changer on its own.

 

[theMeat]

Couple of things I will share.…
-Any dc pump I’ve tried, which includes two eflux, will not hold up to hi head. Works great at first. Then after 6, 9, 12 months tops, gph falls off to laughable amounts.
-One way valves will not make a seal once crud builds up in pipe, and crud will build up in the pipes.
-Two pumps into one pipe is wasting energy, since one pump is pushing against the other. The one way valves are also not working as intended in this application because pressure /forward flow is keeping the valve open and one pump will surely pump more than the other, which will allow back flow. It’s just that the open end of the pipe on top is the path of least resistance.

Imo, and ime,….
-Run a single pump and pipe to tank, or drill a second hole into tank for second return. You can have a second pump, on standby, ready to be installed if needed.
-Drill a small hole on top of return just under water surface to act as a siphon break.
-Use a pump rated for high head, like an Iwaiki or the likes, or at a minimum use an ac pump.

To answer your question, yes, a larger diameter should help flow.