Bulkhead question.

[college429]

How much water can a gravity fed 1 1/2" bulkhead over flow handle?
I am trying to decide what capacity pump to get. I don't want to get a pump that is too powerfull for my over flow.

Thanks for your help.

[Spuds725]

The location does matter, although I don't know the capacities.. but if on the bottom of your tank (like a megaflow), you can squeeze extra flow through them--- I'm assuming whoever answers this will want to know this

the drain/overflow calulator might be of help..http://reefcentral.com/calc/drain.php

[college429]

Thanks spuds.
The overflow is at the top of the tank. If I am reading the calculator right I can run a pump at up to about 1300 gph with a 1 1/2 inch bulkhead overflow.

Can anyone confirm I am reading this right.
Thanks for your help.

[dwdenny]

I think that would be pushing it. I have two 1" bulkhead and I think that I can push about 1000gph at most. Same setup i think as you. Calfo Overflow with 2 1" bulkheads to drain to the sump/fuge. HTH

[Spuds725]

Thats what I read also however, you might want to give yourself a margin of error in case your pump puts out a bit more or you get a little bit of blockage...

Possibly even running dual bulkheads of that size but at different heights--- you could throttle back the lower one a bit if you have noise issues and then the higher one could be used as your "emergency overflow" if you experience blockage of your main drain...

I am a firm believer in redudancy as a means of reliability...

Please get others opinions in this... I'm far from an expert... just a message board wall fly that has read thousands of posts.... ;)

Good luck...

//edit//
<a href=showthread.php?s=&postid=7114861#post7114861 target=_blank>Originally posted</a> by dwdenny
I think that would be pushing it. I have two 1" bulkhead and I think that I can push about 1000gph at most. Same setup i think as you. Calfo Overflow with 2 1" bulkheads to drain to the sump/fuge. HTH

realize the area of the opening is not linear but exponential... so a 2" bulkhead is actually 4 times the opening as a 1"

area = pi x r^2

a 1 1/2" opening is 2 1/2 times bigger then a 1"

Opening area
0.25 0.049
0.5 0.196
0.75 0.442
1 0.785
1.25 1.227
1.5 1.767
2 3.142


That being said, I also believe running 1300 gph through a single 1 1/2" bulkhead would be pushing it. :)

[college429]

I just got this used 180 gallon standard AGA tank.
It is DIY drilled with a single 1 1/2" bulkhead near the top.

The calculator seems to suggest 1300 might be the max. But I certainly would aim for something less than that for a margin of error. A Pump mabye rated for 1100 max?
I would also put a ball valve on the return line to slow it down if I over shoot the max.
How does that sound to people?
Thanks all.

[jh2pizza]

I have my return running up and over my tank and use the original 3/4" return drilled from the factory as my drain. I use a gate valve to adjust the flow and run over 1200 gph through it. The factory drain is fitted with a Durso pipe and is only used in case something plugs the smaller drain. The 3/4" drain is used as a siphon and is so much more efficient and quieter than the original set up, not to mention, I have a redundant backup drain.