# How to calculate drain size?



## sig (Dec 13, 2010)

i am looking to make new set up with 40G tank and 25g sump. Are there any rules to calculate size of the drain?
Thanks

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## ameekplec. (May 1, 2008)

You just need to have an idea about the flow rate you want through the sump/return pump. You'll probably have 1 - 1.5" drains, and a 3/4" return?


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## sig (Dec 13, 2010)

ameekplec. said:


> You just need to have an idea about the flow rate you want through the sump/return pump. You'll probably have 1 - 1.5" drains, and a 3/4" return?


Thanks, but...
This is a good question for which I do not know answer and I just want to know your opinions based on experience.

I already made a mistake with my sump in the basement. I can not estimate GPH what I have, but I assume it is very high. 
1.5" drain plus water drops down from ~ 13' creates very high flow. The pump is also so powerful that I should run ½" line from return, back to the sump. It creates flashes and high evaporation rate. As result of the flashes, I even need to add some saltwater during a week, since by trying to keep water level in order, I add ~ 1.5 G per day of the RODI water. This is for total of 160G. Otherwise salinity is reduced during a week. 
I know, I can change pump and close drain valve (which is not good idea), but I just gave up for now.

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## ameekplec. (May 1, 2008)

You can restrict the drain (not the greatest - but I do it for my herbie), or you can throttle the tank back by putting a valve on the return (not intake side) of the pump.


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## sig (Dec 13, 2010)

I have a valves there, but I am not sure that it is safe for the pump. Now bypass valve is open even more than you see in the picture.
Anyway will try it tonight, since I should resolve this cituation somehow.
Thanks Eric



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## bioload (Oct 20, 2009)

sig said:


> i am looking to make new set up with 40G tank and 25g sump. Are there any rules to calculate size of the drain?
> Thanks


Make sure that the drain is oversized for the return .

How about this?

http://www.efunda.com/formulae/fluids/draining_tank.cfm#calc


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## sig (Dec 13, 2010)

bioload said:


> Make sure that the drain is oversized for the return .
> 
> How about this?
> 
> http://www.efunda.com/formulae/fluids/draining_tank.cfm#calc


since you will do it, I am worry free for now. But thanks for the link

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