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New circulation pump

Discussion in 'General Plant Topics' started by scottward, Mar 26, 2010.

  1. scottward

    scottward Guru Class Expert

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    Hi.

    I am thinking of buying a new circulation pump for my 6' planted tank (~400 litres; 100gallons).

    The pump would be positioned underneath the tank in a cabinet (~1m head) and is feeding water into an AM1000 hooked up in 'dual venturi' mode.

    I would like to buy a circulation pump that can be adjusted. I would possibly like to hook up a second AM1000 down the track to help with CO2 in my tank, running the second AM1000 in parallel off the same water pump.

    At this stage, I'm thinking the Eheim Compact Plus 5000, as it is a good brand and seems to have plenty of 'power' in reserve for my needs.

    Is this a good pump?

    I also notice that Eheim sells a universal water pump range - but I don't think it is possible to regulate the flow from these and they only go up to about 3000lph which might not be enough for me to run 2 AM1000's with 1m head?

    Any thoughts?

    Scott.
     
  2. shoggoth43

    shoggoth43 Lifetime Charter Member
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    Any pump can be throttled with a ball valve ( preferably a gate valve instead ) on the output line of the pump. Never restrict the inlet of a pump.

    -
    S
     
  3. scottward

    scottward Guru Class Expert

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    Would restricting the flow with a ball valve cause heating problems when using the pump externally?

    Out of interest, what difference does it make restricting inlet vs outlet; wouldn't this be exactly the same thing??

    Thanks for help shoggoth.

    Scott.
     
  4. shoggoth43

    shoggoth43 Lifetime Charter Member
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    Ball valve won't be a problem. The gatevalve would be the preferred method as it's easier to return to the same position and has finer control because of the way it works. That said, most use ball valves as they're easier to find.

    Inlet restrictions starve the pump of water. This can lead to issues with cavitation and damage ( if the pump is strong enough ). Since the pumps we tend to use are not so powerful you will get away with it, but you may end up running the pump a little hotter than expected with a slightly higher current draw. You may not see any practical difference. Whenever possible, go with at least the full inlet size to the pump. Gerryd has a thread here on the reeflo pumps somewhere and you can see how giving the pump the full inlet path to the pump dramatically increased flow. In his case it made a marked difference.

    -
    S


     
  5. Gerryd

    Gerryd Plant Guru Team
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    Hi Scott,

    No, it is NOT the same as I have learned :) If you restrict the INLET to a pump, that affects the OUTLET because the pump can only pump out what it has coming into it.

    If a pump is rated for 100 gph as an example, but you use very thin tubing that cannot DELIVER 100 gph, the pump will be starved for water and not work optimally. That is where heat issues come in as the pump is working harder than it has to.

    Remember that tubing size dictates how much water is actually flowing, regardless of the size of the pump or filters....

    So, if the pump has a 3/8 connection, size up to 1/2 tubing or bigger. Always size up in plumbing.......

    A gate valve is nice for fine tuning flow, but a ball valve will serve well for your purpose.....

    As an example one of the biggest issues with the AM1000 reactor is the small inlet/outlet size. You can't flow 500 gph through a 3/8 pipe!
     
  6. scottward

    scottward Guru Class Expert

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    Ah ok, thanks for the info, it makes sense now that I've thought it through a bit more.

    I suppose I could dig it up in a thread here somewhere...but does anybody know what the actual maximum flow you can put through an AM1000 is??

    I know that Tom hooked up 2 AM1000's on a client tank once before - does anybody know if he hooked them up with a seperate pump each, or hooked them up in parallel of a pump powerful enough to feed each unit with a decent water flow? Hooking the AM1000's up in serial seems pointless...

    Scott.
     
  7. inkslinger

    inkslinger Guru Class Expert

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    I've ran a Mag 5 500gph pump with my AM1000 in a close loop. I would think a High Pressure Pump would be needed to handle the back pressure when you install a valve to throttle back the flow to your AM1000's?
     
  8. shoggoth43

    shoggoth43 Lifetime Charter Member
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    Unless you need the pressure to shove the water through something in the first place, there's no reason to go with a high pressure pump that you're going to throttle down. i.e. if you're going to run it through a CO2 reactor and throttle it down, a simple circulation pump is fine. There's little actual restriction in the AM1000 and the only reason to use high pressure is to try and shove more water through the tubing than "wants" to flow. You'll get away with more up to a point before you blow out the tubing or likely the reactor. If you try this, make sure you throttle the flow as close to the pump as you can so you restrict the pressure BEFORE you get to the reactor. AFAIK, none of the CO2 reactors are really designed for any real amount of pressure. They all seem to assume free flow with maybe 4-5 feet of head pressure max back up to the tank.

    If you need to go through a cannister filter with high backpressure, or a mazzei injector, then the higher pressure would be needed no matter what tubing size you use. In most cases the higher pressure pumps use more electricity to do their job so if you don't need one there's little point to using them. However, throttling them down does drop the power consumption somewhat so if that's what you've got you may as well try it.

    For flow rates, here's a good recommendation.

    http://www.flexpvc.com/WaterFlowBasedOnPipeSize.shtml
    You should probably expect no more than ~4-500GPH through an AM1000.

    This site suggests closer to 3-400GPH
    http://watergarden.com/catalog/pond-pump-tubing.html

    Replacing the fittings on the AM1000 will get you more flow, but as to how well you can dissolve your CO2 at the higher flow rate and distribute it is another matter.

    -
    S
     
  9. Gbark

    Gbark Guru Class Expert

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    I agree with the most, but i would not use a gate valve, they are not very good for flow control, they are normally used for fully closed, fully open applications. the ball valve is a good cheap way to control the flow leaving a pump.

    If you want better flow control then look at a butterfly valve or a needle valve If you know or want to work out what flow rate you require a suitable ro (orifice plate) will be ideal, that way you can use a valve fully open. :)
     
    #9 Gbark, Apr 6, 2010
    Last edited by a moderator: Apr 6, 2010
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