# Drain Line Sizes Based on Return Flow Rates



## sig (Dec 13, 2010)

Found on the Web

"During my research into SW set-ups, I found some really good info on a website that I thought I would share. Based on want I have been able to learn, healthy SW tanks with sumps usually have a flow rate of between 10X to 17X. By that I mean the flow rate of the pump circulates the water in the tank & sump 10 to 17 times per hour. For example, if you had a 100 gallon set-up (tank & sump) you would need a pump with a flow rate between 1000 to 1700 gallons per hour (GPH). When you purchase a pump you will know what size of return line you need by reading the instructions or manufacture's recommendations for the pump. The one thing that I was having trouble coming up with was what size of drain line from the tank I will need to supply the sump with the correct amount of water for the GPH flow rate that I will have.

As I bought my tank, sump, pump, and all the plumbing used as a completed set-up from a guy who was using it as a reef tank, these below calculations match how the tank and sump were set-up for the flow rate of the pump. There are other factors to consider such as the number and degrees of elbows in your drain line which will restrict your flow, but this can be used as a rule of thumb before accounting for other restriction to the flow.

I just thought that maybe others would find this info as helpful as I have.

GPH Drain Diameter size
200 0.58"
400 0.83"
600 1.01"
800 1.17"
1000 1.31"
1200 1.43"
1400 1.55"
1600 1.65"
1800 1.75"
2000 1.85"
2200 1.94"
2400 2.02"
2600 2.09"
2800 2.19"
3000 2.26"
3200 2.34"
3400 2.14"

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## altcharacter (Jan 10, 2011)

This is great since I am thinking about chaning my 30 gallon FW to a SW setup. This helps alot but I would try to give the author some credit since he did the work.

Either way thanks for the info!!


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## bioload (Oct 20, 2009)

Thanks for the info...

http://www.aquaticcommunity.com/aquariumforum/archive/index.php/t-69246.html

I'm assuming those rates are not full siphon?.......I generally try to separate sump turnover rates and tank circulation. Keeping the turnover rate to the sump balanced with the filtration (skimmer, reactors...etc.), and leaving the circulation in the tank to the powerheads.


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## wildexpressions (May 3, 2010)

good post.

I'd just like to add that a lot of what any given diameter of pipe can flow has a lot to do with the design of the overflows as well. 

For instance in my area we are seeing these 120 to 200 gal+ tanks that use stand pipes and in that particular design a 2" stand pipe doesn't seem able to do any more then 350 to 400 gph ( and is very noisy doing it). I've never actually flow tested any of them but I'm basing it on the pumps rated output at head and the fact that people are having to throttle their pumps way back to avoid overflowing the system. I've stopped by 3 different clients now all with the same issues on these discount tanks.

The pipes create a 3+ foot drop for the water and water falling that distance though tube will suck large amounts of air. Same idea as an air powered under gravel lift tube but reverse everything and you have a water powered air pump.

In tanks that are drilled in the back side the way the plumbing is done can have a huge effect as well. I've seen plenty of poorly designed 2 inch plus over flows that backed up well before hitting 100 gph (although that is usually an air after water issue)

Anyway, I just wanted to make the point that there is quite a bit more to consider then the max flow rate of a given diameter of pipe. Plumbing is pretty simple once you've done it wrong a couple of times


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