Flow through pipe

[Duane Fagan]

Hello hello so I'm looking into the seamless sump by Customaquariums.com......question is what size pipe would I need to handle 3600-4800gph of flow from tub to tub

 

[Slocke]

This is dependent on velocity; the smaller the pipe the faster the velocity and vice verrsa. Q=v*A where Q is flow, v is velocity, and A is cross sectional area.

So 4200GPH (308in^3/s) in a 1" (0.25pi=0.785in^2) pipe would have a velocity of 308in^3/s / 0.785in^2 = 392 in/s =32.7ft/s

but 4200GPH (308in^3/s) in a 2" (1pi=3.14in^2) pipe would have a velocity of 308in^3/s / 3.14in^2 = 98.0 in/s =8.17ft/s

The greater the velocity the greater the forces are acting on the pipes. I'm not sure what the optimum velocity is but in my system I have two 1" pipes working at about 500GPH each. Which is only 3.41ft/s

A 3" pipe would get you 3.63ft/s with a flow of 4200GPH

 

[Duane Fagan]

Mind blown I was never good at math so if you can dumb it down to 6th grade basically can a 1.5 or 2" pipe handle 3600-4800gph of flow going from tub to tub (horizontally) so the last tub where the pump would be doesn't run dry?

 

[Slocke]

So according to google water flows horizontally through a pipe at 10.0m/s= 32.8ft/s. You want your horizontal flow to exceed your pump flow of 3600. As said above 1" would give you 32.7ft/s which is too low. 1.5" would be 14.52ft/s which gives you a nice half factor for safety.

In other words 1" no. 1.5" yes.

But I would love someone else to back me up. I'm an engineer but not a plumber so my knowledge is more theoretical then practical.

 

[Duane Fagan]

Thanks man I appreciate your help on getting me to understand this stuff so to be safe a 2" pipe would make me sleep better at night or even two 2" pipes per tub