Return pump priming needed?

[whatcaneyedo]

Originally Posted by banditpowdercoat

Adding outlets does nothing to increase head pressure. Neither does pipe size. A 6" diam pipe will have the same head pressure as a 1" pipe of same height.

Thats quite the statement and contradicts everything I've seen and read. Do you have any sources to back it up?

[banditpowdercoat]

Ya, Any plumbing manual. Head pressure is only the verticle height. It does not matter the diameter of the pipe. Now, when talking Flow restriction, that goes by pipe diameter, But if you have a 1" pump outlet, Doesnt matter if its 1" all the way up, or if it expands to a 6" pipe, the head pressure at the pump will be the same. GPM flow may be affected by the smaller pipe and friction loss, but not head pressure.


Think of it this way, Head pressure is in PSI, right? So, take a 1"x1" column of water 6' high. It has X head pressure. Now take a 6" pipe, Head pressure is still measured in PSI. Yes, the pipe is larger, but you only take a 1"x1" section of the pipe for figuring head pressure.


Or, take my fish tank, 150g, 5'x2'x2' Its 2' high, does not matter that the tank is 5' long, or 50' long, the pressure(PSI) at the bottom of the tank is the same, Its dependant on height, not LxW


Hope that helps

[whatcaneyedo]

So your argument is simply that we were using the wrong terms, calling everything head pressure where as theres two different concepts: head pressure and flow restriction. Like the way everyone calls all sea slugs nudibranches... Never mind then.

I blame Delbeek and Sprung for mixing me up. "Head pressure refers not only to the vertical distance a pump must push the water, but also any resistance to flow created by pipes, fittings, and valves." The Reef Aquarium Vol 3

[mark]

What we commonly referred to Head maybe more accurately is Dynamic Head, being the Static Head (the height part) plus friction (from couplings valves etc), and is for example what the RC Head Loss calculator, calculates.

[banditpowdercoat]

But in the instance in this post, where you said to close off the other outlets, above the check valve, that would not have made a difference in the head pressure keeping the check valve closed.