Pump size

How do you know what size pump you need on your tank? I have a rio 17 HF on my tank right now but I am going to buy a new pump this one is going out, I was thinking about getting smaller pump, but how do I know how what size to get, I have a 40 gal breeder with a 30 gal sump with two output and two returns.

 

Do you know many GPH can your overflow handle? its right under your tank so it the head height shouldnt be to much of a issue.

Your current pump does 620gph so i wouldnt go any less unless you have restriction in your over flow a mag 7 or mag 9.5 would do the trick.

 

I would try to find a pump which can pump out 4-6x your total system water volume, at 3-4 foot head (depending on the height of the top of your tank).

Lets say your 40B is on a 36" stand...your tank is 18" tall. so for your particular tank 40B with a 30g sump you want about 400 gph at 5 foot of head pressure(pumping up 5 feet to top of tank). If the stand is 30" tll then you won't need as big of a pump.

If you want added water flow/turnover in your display tank then I would go for 10x turnover rather than 4-6...add some loc-line to the end and add a flare nozzel.

 

No need to have an oversized pump for your return. You will probably end up dialing down the return pump anyway...

 

Thats true I had a 4mdx 1500gph little giant on my 75gal and man would that thing move some water lol

 

I can adjust how much flow goes into the tank and I can also adjust the drain pipes as well, Im not sure how many GPH the overflow can handle but I can adjust how much goes in and out.

okay that makes sense. right now when I do water changes and shut off the tank it ills back up to quick and the DT will flood I have to keep adjusting to get it right and its annoying I want to be able to shut off the pump and be able to turn it back on and just have it start running again.

 

haha. I could imagine. If you want the big pump for added water movement in the display then go ahead. I just wouldn't get anything bigger than 10x otherwise water will move through the sump too fast.

 

I think thats my problem now.. it think it is too big for it I have to constantly adjust everything its really hard to leave on vacation knowing that the power could go out and then come back on and flood the DT.

 

I would never go that big on a return pump. The general rule is 10x the SUMP'S VOLUME. You have a 30 gallon sump, but I'm sure it doesnt run full, so just say that it holds 20 gallons in the sump. You would take 20 x 10 = 200 GPH.

Now as seano was talking about head height. The higher the pump has to push water, the lower the flow will be. Also 90 degree elbows and tees, etc. will restrict the flow even more. With your setup, figuring 5 feet of head is probably close enough. A Mag5 is 250GPH at 5 feet of head, and would be what I would recommend as a replacement.

I dont know how your sump is setup, but if it isn't a center return, and you cant control the flow through the fuge seperately, then you definitely dont want too big of a pump, since you want flow through the fuge to be slower so you have more contact time with the macro.

 

We've found the answer to your plumbing issue you've been having.

The overflow(aka drain) line should not be restricted (unless you have a separate line going to your refugium). Our overflow lines (or most drilled ones....I think yours is drilled, correct?) are gravity fed. If you turn off the return pump, then water will no longer go to the display tank. If no water is supplied to the display then your 'cycle' of water movement stops. The sump should allow enough room for the small amount of water in your overflow to drain into the sump.