calculating head pressure and GPH for pump

Discussion in 'Filters, Pumps, etc..' started by schackmel, Nov 19, 2009.

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  1. schackmel

    schackmel Giant Squid

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    my mind is racing tonight and I am trying to figure out head pressure adn GPH for my replumb.

    First of all, I am going to drop my sump into the basement...planning on a 150g rubbermade sump (as I am going to eventually finish off the basement and add a 300 FOWLR tank inwall...so thought might as well plan ahead. Plus I am working in a LFS so I can get a great discount now ::)

    anyway...I started by calculating the head pressure. This is just an estimate...I figured 9 feet from sump to basement ceiling, and then another 5 feet from floor to overflow. Then I have 2 overflows that are about 5 feet apart. Then I figured that I would have at least 4 90 degree angles.

    So I estimate my head pressure being around 28.

    I have a 135g tank, and with a 150g sump that would be 285 gallon total water volume. I know that reef tanks is about 10-30 times turn over. So I used 30x at first and it gave me a whopping 8550gph with head pressure 28.

    when I decreased it down to 20x it was 7700.

    Still way more then I can find a pressure pump for :confused:

    I know I am doing something wrong...help?
     
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  3. coylee_17

    coylee_17 Fire Goby

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    quick question and maybe I can help. You using 1" returns?
     
  4. Powerman

    Powerman Giant Squid

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    9+5=14. 4x90 OK. but I'm assuming the returns are teed and two 90s on each. In general a 90 will be a foot of head, but the bigger the piping the less restriction. Plus split.... eh...3 feet. Call it 4 though.

    You are looking at 18 feet of head. Not sure how you get 28.

    And you only need 10x water turn over at most going through your sump. you need more in your tank. But you definitely do not need 30x going through your sump. Your sized skimmer will probably only process 500 GPH max.

    So even at 250 x10, we are talking 2500 GPH. But your "tank" is only 135g. So 10x135 is only 1300gph. Now you only need to find a pump that can flow 2000gph at 18 feet of head. Even that sounds like a lot to me.

    Most times I have heard any where from 6-9 times tank turn over. I know I'm only doing about 600gph on my 90g and that is a lot.
     
  5. coylee_17

    coylee_17 Fire Goby

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    I'm with powerman, I dugout my charts from work and I get 18', 14' of vertical pipe, and allowing 12" for each elbow.
     
  6. coylee_17

    coylee_17 Fire Goby

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    That's assuming 1", add 2' if using 3/4"
     
  7. schackmel

    schackmel Giant Squid

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    I was planning on 1" pipes...but I dont know as I am in the early, early planning.

    this is where I got the info on calculating head pressure
    Calculating Head Pressure: Determine Your Marine Aquarium's Back-Pressure and Flow Rate | Suite101.com

    you are right..definately not needing 30x in sump...

    stupid question....how do you figure out how much flow through the sump..I did not figure that in the equation. The article I was referring to did not differentiate that (or I just missed it)

    thanks again. This time I am going to take my time and do everything right hopefully. Last time I just took what the LFS did and quickly found how messed up it was
     
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  9. Powerman

    Powerman Giant Squid

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    Ya, that is pretty liberal with calculations. You do not need to figure horizontal piping. Yes there is a bit of head loss, but not like gravity. Just figure vertical, unless you are going 30 feet across a room.

    Necessary flow in a tank is a different story. 30-40 times is not uncommon. But that is from power heads.

    When we talk about tank turn over, we are talking about how often the tank water is passed through the filter. Canister, skimmer, W/D. Generally 6 to as much as ten times an hour is good.

    So how much you need through your sump is of no consequence. What do you have in your sump? A skimmer, fuge, W/D, canister???? All I have is a skimmer and a fuge. The fuge needs less than 100 gph, and my skimmer will only process 200-300 gph. So really anything over 400 gph is just wasted flow. It is just circulating, nothing is really happening.

    So what you have is a 135g tank, and you want to circulate that water so many times an hour through your filter system to keep it clean and oxygenated. For flow in the tank for corals and fish and to keep it oxygenated you want a couple power heads. but it does not need to go through your filter.

    So seriously, 1000gph through your sump will be plenty AFAIC. Penty of pumps can push 1000gph with 20 feet of head.
     
    Last edited: Nov 19, 2009
  10. schackmel

    schackmel Giant Squid

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    thanks! sounds much better! LOL