What size return

Ok my new setup is goign to go as follows, 3 1inch returns, 2 will feed into my sump which is 30g, and the 3rd return which will be in the middle of the other 2 will go to the fuge with a ball valve to be a slow drain. The fuge will be a seperate tank which will gravity drain into the sump. Im going to do dual return on opposite sides of the tank. The tank is a 75g and will be using a calfo overflow, im set on the coast to coast so dont try and talk me out of it.

I was thinking of a mag9 or mag12, the return will only run the return and nothign else.

 

If the sump is directly under the tank I would probably look more in the range of a Mag 7 personally. That will be around 400-500gph after head loss which is good for a 75g with a 30g sump IMO. Also since the refugium is also draining into the sump don't calculate that as separate flow because the overall amount of flow from the return pump is still all making it back to the sump at the same time.

 

Dang never thought about a mag7, even if its running dual returns ran with pvc, I was estimating a total of about 7ft after footed with pvc (thats both tubes added together).

 

I would go with the larger pump for future expansion (reactors, chillers..ect) You can always dial a pump down with a valve but you can't get more out of a undersized pump. I would hook up a manifold just in case you need it later on.

 

When you said 3 returns, you described drains. Returns go from the sump to the DT. If you want two returns going to the DT on one pump and have 7ft. of head room for each return, you will need a much larger pump. Think about it, you will have two columns of water being pushed up 7 ft. not 1. If I wanted to do this, I would use two pumps, one for reach return and I would use either two mag. 7 or two mag 9s depending on what your overflow can handle. I would also use 3/4" returns as the fittings on the mags are 3/4" and you will loose a lot more gph going from 3/4 to 1". At 4 ft. two mag 7s will return about 900gph, the mag 9s about 1600. You may also want to consider an inline pump then splitting that.

 

Ya 3 drains at 1 inch so gph im really not worried about it being to low for the return, for instance not scared to put a mag12 in there and it not drain quick enough. I was considering the 3/4 return lines, 1 main 3/4 line coming off the mag then to a T to the 2 returns that will be facing on opposite sides of the tank. I really dont want to do 2 pumps since I dont want to get a chiller yet until I have a 180+ size tank since I would have to sell my unborn son to get one. I think max feet it will be going to total with both return lines is bout 10 + or - 1 foot. I want a good turnover in the tank with enough flow from the returns and the k2's to be good. If I have to upgrade and get 2 more k'2 for a total of 4 then I will.

Looking at my tank now and re-design of my sump I may just have 2 returns at 1 inch. Also I just looked at the mag's and from what it looks like a mag12 would be a turnover of about 600 at 10ft. Does this sound like a good pump to get, If so then I will buy a mag12 and then a mag 9.5 as a backup or incase the mag12 is way to much water power and the overflow cant handle that much water back in the tank at the same time.

 

Oh, I forgot about the dual returns, that really adds a lot of head loss. You might want to go with the Mag12 and dial it back if you need to. just adding another exit to the return pump adds head loss along with all the extra plumbing.

Whatever pump you decide on I would get the same pump as a backup, but only so you have one in case your main one breaks for some reason at an inconvenient time (like right before you go to bed you turn the pump off for some reason and then it never starts back up). Dialing back these pumps is not a bad thing, just throw a gate valve on it IMO.

As for using the returns for flow, if you don't want to have to worry about a chiller then the best way to save heat on pumps is to use larger powerheads, using return pumps for flow is extremely inefficient because you are fighting gravity and friction in the plumbing the whole way. Look at the wattage on in-tank propeller powerheads like Koralias and the GPH they push vs what you see in a return pump and you'll see what I mean. The more watts each pump uses the more heat it's potentially adding to the tank.

IMO return pumps are for getting water to the display tank and back down for filtration purposes, as well as potentially running other things like reactors etc in the sump if you want to manifold it like Otty mentioned.

 

lol ok mag12 ftw, ill buy 2 of them or maybe I can locate them locally from someone used since 120-140 brand new sux but o well. Ya I dont want to use the return for all the flow and will get more k's if needed. I want this tank to be my dream tank till I move to a house in 3 years.

 

Well im looking at getting 2 of the rio rio20hf, Its showing 870gph at 6ft which im goign to be running it at 10ft so it shouldnt be 870gph at that height. What do you guys think, i cant justify spending 300 bucks on 2 pumps when the rio I have now is runnign great (knocks on wood)