How to compute pump head (refuge above)?

[joelr]

Help.
(If this has been answered, please direct me to the answer - search is almost useless and I'm waiting for my premium membership to become active.)

I'm building an aquarium with the refugium above.
Essentially:

30x15 x 14H sump, bottom 1" above floor.
30x15 x 18H main tank, bottom 30" above floor.
30x15 x 8H refugium, bottom 60" above floor.

I'm planning on a PVC return from a submersible pump in the sump using two 45degrees, going up and T-ing at the main tank to continue on to the refugium. After the T there are two ball valves (to control flow to both refugium and main tank). At the top there would be a 90 degree to turn over top of tank and then another 90 degree to go down into tank followed by one more to flow in tank. Similar setup in the main tank... turn the pvc to go down into the tank and then turn again near the bottom to flow into tank. (Critiques welcome)

Since the refugium flow rate will be significantly less than the main tank flow rate, what sort of head will I have for this setup? Or is it better to plan two pumps - one for the refugium and one for the main tank?

Thanks!
Joel

[rustybucket145]

I'm not sure I'm following you 100% on this...

Would make life easier if you could lower the fuge to below the main tank.

But if you must.... You will need to valve each individual line (to fuge, to tank) this will allow you to turn the fuge up and the tank down. With both fully open I doubt you will have any flow to your fuge. There's no need to have two pumps but you will need a pretty decent pump to push a 60" head.

You need to start by determining how much flow you want through the main tank, and how much through the fuge. Then I can help better.

[kgross]

What I would suggest you do, is plan on putting all of the flow into the fuge, then let the fuge drain into the main tank. Now to really figure out your head loss on your pump, the total head will be the 60 inchs to the top of the fuge, plus frictional losses. With your valve on the main tank, you will be able to decrease the amount of flow going into the fuge, but unless you open it up enough to stop the flow into the fuge you will still have the same static head pressure since the pump will still be lifting the water 60 inches.

Kim

[joelr]

Hmmm. Now I'm more confused.

What I really want to know is *how* to compute the head with one pipe but two outputs at different locations (heights).

But. For sake of example, I think I'm planning on the fuge flow rate to be 3x (45 gph) and the main tank to be 10x (350 gph).

I also understand that for computing the basic head height you compute from the *top* of the sump water. So I think we can subtract a good foot from the 60 inches to get to the top of the fuge as well as a foot subtracted to get to the top of the main tank.

Specifically then: Actual head height to top of refugium will be 5 feet and a bit less than 3 feet to the top of the main tank.

It's sure sounding simpler to use two pumps :-).

(I certainly don't want all the water going to the fuge - the flow rate there would be more than I want for its purpose.)

Cheers,
Joel

[kgross]

Without lots and lots of math you can not do it. But you can come up with a very close guess to the total water flow from the pump using just the line to the fuge for your calculations. The water that you let out of the line to go to the main tank, will not effect the static head pressure. only the dynamic friction loss. So you can come up with a number for the total flow if it was going into the fuge. Your valve on the main tank, will divert some of that flow into the main tank. It will only effect the head pressure in that the water that comes out of that valve will not add frictional head loss through the extra pipe going up to the fuge.

So use the head loss calculator on the main page and ignore the outlet into the main tank. That will give you total flow. Then with a valve on the outlet into the main tank (not one on the fuge it will reduce your total flow), you can divert some of that flow into the main tank. So if your calcutaions show that with your pump you can put 500 gph into the fuge, you can divert 400 gph into the main tank and still have 100 gph going into the fuge.

Kim

[joelr]

Thanks, seems like a reasonable approach.
Joel