Closed loop and back pressure from display???

lessthanlights · 10/28/2006, 02:17 AM

My closed loop has one 1.5 inch intake and four 1 inch outputs on my 36x24x24 custom 90. I'll be using a Ocean Motion Super Squirt and a yet to be determine pump. The head is about 4 feet and I want about 2500gph. Now the question. Do I need to calculate the back pressure the display tank will exert into the closed loop returns. Obviously the head will slow the gph considerably but is there a "head" created from the weight of the water in the tank trying to force water down the returns? If so do I need to factor that in? And please do not refer me to the head calculator- I've spent hours and hours working out different scenarios with it.

Tang Salad · 10/28/2006, 03:28 AM

You won't have 4 feet of head on the CL.

As you guessed, the pressure feeding the pump will push the water up to the height of water in the display.

Sorry, I'm not good at explaining this, but you don't need to calculate for that much head pressure.

Somebody else will come along and explain it better.

jdieck · 10/28/2006, 03:29 AM

Actually no, The same head pressure acting on the inlet acts on the outlet so there is no static presure diferential due to height but you will have dinamic head pressure drop caused by the friction of flow in the piping elbows, unions, valves and such.

10/28/2006, 02:17 AM	#1
lessthanlights Registered Member Join Date: Aug 2003 Location: Duluth, MN Posts: 606	Closed loop and back pressure from display??? My closed loop has one 1.5 inch intake and four 1 inch outputs on my 36x24x24 custom 90. I'll be using a Ocean Motion Super Squirt and a yet to be determine pump. The head is about 4 feet and I want about 2500gph. Now the question. Do I need to calculate the back pressure the display tank will exert into the closed loop returns. Obviously the head will slow the gph considerably but is there a "head" created from the weight of the water in the tank trying to force water down the returns? If so do I need to factor that in? And please do not refer me to the head calculator- I've spent hours and hours working out different scenarios with it.

10/28/2006, 03:28 AM	#2
Tang Salad Algae skeptic Join Date: Oct 2006 Location: 78702 Posts: 3,098	You won't have 4 feet of head on the CL. As you guessed, the pressure feeding the pump will push the water up to the height of water in the display. Sorry, I'm not good at explaining this, but you don't need to calculate for that much head pressure. Somebody else will come along and explain it better. __________________ Your algae is not special. Current Tank Info: TBD ADA 120-P SPS NLPS

10/28/2006, 03:29 AM	#3
jdieck Registered Member Join Date: Dec 2002 Location: Maumee, OH Posts: 15,673	Actually no, The same head pressure acting on the inlet acts on the outlet so there is no static presure diferential due to height but you will have dinamic head pressure drop caused by the friction of flow in the piping elbows, unions, valves and such. __________________ Did I write what I wrote? What the heck am I talking about! Well..... Nevermind. Current Tank Info: 225 gal reef, DSB, 40 g sump w/ LRT100 return, 37 g pre-sump, 3 MH 250 W 15K, 4 96 W PC dual actinic,ETS 1500 Skim.w/LRT70, 20 lb Ca R., 40 W UV, 1/3 HP chiller, two 350 W Htrs, Neptune II Cont., 330 P LR/ 330 P LS. 55 gal Refugium