Vertical drain rate for salt water

[aquariumdude]

I am in the aquarium business and need to determine what the gravity vertical flow rate of salt water would be through 1", 1.5", and 2" schedule 40 pipe. These are fairly common drains, with what I would categorize as turbulent flow. I need to upgrade a pump in a 500 gallon salt aquarium and want to ensure that the gravity flow drain 30" above the bottom of the tank can keep up with the flow. I have been running approx 1200 GPH to date with a 1.5" drain keeping up quite nicely. I want to increase throughput to 2000GPH. Will the drain keep up?

 

[zekeman]

From the formuls
V^2=2gh
I get that the velocity of the flow for 30 inches of drain height is
V=square root of 2*g*30/12feet/sec= 12.68*12*3600=547,776"/hr
If you need 2000GPH=2000*231in^3/hr=462,000 in^3/hr
Then the minimum area of the crossection is
462,000/547,776= 0.84 in^2 or an inside dia of about 1 inch
1.5" sch 80 should do it easily.

 

[eromlignod]

I wouldn't use schedule 80 pipe just because the ID is closer to your calculation. A 1-1/2" schedule 40 pipe has a larger ID with the same OD and is considerably cheaper (like half the cost or less) and easier to get at an ordinary hardware store.

Don
Kansas City

 

[zekeman]

Sorry, I didn't mean schedule 80, not for a drain.