Drain Line Sizes Based on Return Flow Rates

[Cliff]

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”

[Dave66]

My three reefs have a turnover rate of 14 to 16 times an hour, plus I employ large sumps, up to 40 percent of aquarium size, so massive amounts of marine water is moved per hour by mag drive pumps.

Dave

[Cliff]

Thanks Dave, I'm glad I'm really close to your set-up. My flow rate will be approx 14 times (accounting for some wear on the pump). But I'm only at approx 25% for the sump size. I am planning on up-grading the sump later on and have disigned my tank stand to accomidate the large sized sump when I have the $$$ for the up-grade.

I was hoping to get lucky at one of the local aquarium society’s monthly auctions and find a old used 40 or 50 gallon tank I can make into a sump for really cheap.

[Dave66]

Hit the yard and estate saies Cliff, they can be a gold mine for cheap tanks. You'll see a whole flotilla of 10 gallon tanks, but keep looking, the larger tanks are out there. I've found a glass 50, a 90 missing a side pane that I had replaced. Tank was two bucks, plus 20 for the local glass shop to cut me a replacement pane. You find odd tanks too, like a 33 gallon acrylic tank I paid a dollar for. I pass on odd shapes like cylinders and hexes. Tanks you find are usually pretty dirty, but clean up just fine.

Dave

[Crispy]

Cliff, when purchasing a pump, remember that it's rated gph is without head. Meaning it's rated without pumping upwards. 3 or 4 feet of head will drastically reduce what the pump is rated for. Good pumps usually have a graph or something that shows gph at different head heights on their box.

[ILuvMyGoldBarb]

Nice piece of info on the flowrates. My 37gal is somewhere right around 12-14x turnover, but my 46 was much higher. I've always adjusted my flowrates based on the kind of corals I was keeping in the tank. When I keep an LPS dominated tank I tend to stick lower flowrates, however when I have an SPS dominated tank it is much higher. I had a pair of Koralia 3s in my 46 before the seals gave out on it. That was 1700gph total for a turn over rate of roughly 37x. The tank was dominated by 90% SPS corals and I had some amazing polyp extension in that tank.

[Cliff]

Thanks guys.

Crispy:
I bought this pump used with my set-up and the past owner did not have the orginal charts that came with the pump. I actually found a website that will automatically calculate the reduced flow for you. Based on the data you enter, it will factor in the hight & lenght of the return line as well as any elbows in the line if you have used any. I test the accuracy by compairing the results with a few charts I was able to find on-line for other pumps and the data was really close so it looks like a good sourse of info.

The pump I have is actually rated at approx 1850 GPH (if I remember correctly), but after factoring in the hight and lenght of the return with two 90 elbows, it drops to some where around 1600 GPH. As the pump is approx 4 years old, I took a wild guess this would reuced the flow rate a further 15% bringing it done to around 1400. The 15% came from a few posts I read on another forum but I have no idea how accurate that wear rate factor really is.

[Crispy]

^^^ sounds like you've done you homework. nice stuff.