plumbing

well where do you work at so people know. And I am not here to argue with any one so unless U have explaned a closed loop wrong I will never tell somone to hook a pump up like that my fax #is 849-8963 if you want to fax a diagram so I might under stand a little better. Or U can call me directly at  897-2000.

PS if this is your definition on closed loop (closed loop circulation system is... think of a pump drawing suction directly out of the tank and returning it. Quote from Jon)I am wondering if you tell people to do it like this and what your warranty is on your pumps. And I do not appreciate your nonchalant personal attack

Ryan,

I'm sorry if I've offended you...I did not mean to.  Truly, I did not mean to attack you, all I asked was "why do you say that?".  I will aways ask for clarification when I don't understand (or agree) with what someone says.  It might be that one of us isn't clearly understanding the other, or it just might be a difference of opinion.  I hope I never attack someone on this (or any other) forum... life's too short to live it angry.

I'm a chemical engineer at an oil refinery, I don't sell pumps but I do buy, specify and troubleshoot them all the time.  I might not understand why my alveopora is dying, but I do understand pumps. 

I've used closed loop circulation on my tanks before without any undue stress on the pump.  Many people do the same thing... go to reef central and do a search on "closed loop".  To satitisfy your desires, I just got off the phone (508-429-1440, give 'em a call) with Iwaki's pump technical support.  Other then me feeling like a fool to even ask "does it matter if one of your MD series pumps has 5 ft of suction pressure", the conversation went just as I expected.  There is nothing wrong with doing it.  When you call be sure to explain that the water is drawn out of the tank and falls 5 ft to the pump, this gives you 5 ft of suction pressure at the pump.

BTW, http://www.iwakiwalchem.com/ is a better web site, it has the pump curves and installation instructions for the WMD/MD series pumps.

Closed loop systems are very common.  In fact they were in use long before our "sump systems" were popularized.

I too talked to Miguel.  You didn't explain it properly to him.  He thinks you're trying to run the pump with 5 ft NEGATIVE pressure.  You can not operate any pump with negative suction side pressure, it will cavitate.  Cavitation causes impellars and casings to brake or crack.  All pumps need a minimum NPSH (net positive suction head) to operate.  If the suction pressure is greater then NPSH then great (as long as it doesn't exceed the pump casing or seal pressure rating).

What you have when you use a closed loop is 5 ft of POSITIVE pressure at the suction side of the pump.  Talk to him again, tell him you have 5 ft of POSITVE pressure on the suction side of the pump.  Better yet, ask him if he has interent access and send him to this thread... maybe he can participate!

If you are going to put a pump under your tank and have to do all the plumbing for it, why not just put a refugia and sump underneath also?

No problem

... did somebody say nerd?

rfoote, who's the nerd?  I bet you know why token ring networks fell out of favor !  And anyone here who knows the difference between IDE and SCSI, brobably has a pocket protector...  Just kiddin' too.

Jon - I loved token ring!  I won't get into why but imo much more efficient and easier to troubleshoot then ethernet.

IDE and SCSI means you are just a little more educated than most. Token ring knowledge gets one closer, however a true nerd would love configuring an ADSL modem on a 386 running windows 3.1 with 4 Megs of RAM remotely through a BNC connection. Ahhh.....how sweet it is.

Quote: Originally posted by Marcus on 17 June 2003

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If you are going to put a pump under your tank and have to do all the plumbing for it, why not just put a refugia and sump underneath also?

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Let's say I want 8 times tank volume per hour of tank circulation and I want a refugium.  What are your feelings on flowing that much water through the refugium?  I would rather flow a lower amount through the 'fuge (say 1 times tank volume per hour).  There are a couple ways to do this (possibly more).  Let's assume 150 gallon tank (1200 gph tank circulation and 150 gpm to refugium)

One way to do this is to get a pump big enough to circulate 1350 gph at a head pressure of, let's use 7 ft (5 ft vertical head and 2 ft frictional loss).  Now we use a sump that has a refugium that's separate from the tank overflow stream, so not all of the tank overflow has to go through the refugium.  Spill back, from the pump discharge,  150 gph to fuge and push the other 1200 gph back into the tank.  This would require an Iwaki 70RT ($290).

Now let's circulate the same amount of water into the tank using a closed loop pump and a separate return pump for the refugium.  The refugium needs a pump that'll do 150 gpm at 7 ft head pressure (RIO 2100 or Supreme Mag-Drive 3, $30 - $35).  The closed loop needs a pump that'll do 1200 gph at 2 ft head (only have frictional losses).  Use an Iwaki 40RXT ($160).  That's a total of $190 - $195. 

As you can see, sometimes it cheaper to go the closed loop route (the economics get even better with bigger tanks and greater circulation rates).  Also, you never have to worry about loosing suction (priming) or syphoning water onto the floor with the closed loop pump when recovering from a power failure (it's self contained no need for syphon breaks on the return piping).  The drawback is you've got to have room for two pumps and that's two pumps that can have problems rather then one.