Water Pump Size

[mrramsey]

Another question for Cliff

I was reading your plumbing article and had a question on the pump size I should pick up. Had I been the one to drill this tank I would have used 1" bulkheads but alas the previous owner used 3/4" o that is what I have to work with. I believe the drain will handle 500gph easy 400 at the minimum. The return will have appx a 3'6" head height. There will be 2 unions, 2 45's (to compensate for alignment) and 1 90 before the bulkhead. Inside of the tank there will be 3 additional 90's for the outlet. So by using middle of the road numbers from the chart on the blog my flow rate reduction should be about 350gph for the fittings. The pump I was looking at, (Danner Supreme 9.5, specs a flow rate of 740gph at a 3' head height. leaving me with 390gph.

What would you suggest as a pump size? something in the 1200gph range? I am adding in a 1/2" tee and ball valve in the return that dumps back into the sump to regulate pressure in the return line so I am assuming it is better to go bigger rather than too small?

[Cliff]

Sounds like you have a good goal for flow through the tank. Ideally for a 72 gallon FW tank, you would want about 5X flow for around 350 ghp which is what you are already aiming for.

If you have a ¾” bulkhead flange then I would stick with a ¾ line and fittings for the whole return line. That would limit your choices in return pump size to around a maximum of 1400 to 2000 gph. With an estimated loss of 840 gph (listed below), you would need a return pump of around 1400 gph (minimum). You can’t get that much flow through a ½ inch line
I would suggest your best option would be a return pump like a mag drive 1800 return pump. This can be used inside your sump and externally as well should you drill your sump as you were thinking about. The below link shows which pump I am talking about. There are many on-line stores in the USA that sell this pump as well as many others. With your planned bypass line, you can adjust the flow to match your maximum drain line flow rate and balance the system.

http://www.jlaquatics.com/product/wp...ater+Pump.html

Estimate flow loss:
4 feet head hight loss – 450 gph
2 unions – 10 gph
2ea 45s – 80 gph
5ea 90s – 300 gph

Edit: I'm not 100% sure I understood correctly all the fittings on the return line so I listed them about, just incase I did not understand your above post correctly

[mrramsey]

I'm not 100% sure I understood correctly all the fittings on the return line so I listed them about, just incase I did not understand your above post correctly

Yes you got it right Cliff!. Thanks for the clarification I will go with the mag drive 18.