Sump/overflow question

The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.


Aquarium Advice Addict
Jan 1, 2004
I thought I had asked this before, but maybe someone else asked it and I read it somewhere...anyway, Im setting up a 100 gallon reef (eventually) which is 5 ft long and will have the following:
Southdown sand (100 lbs)
LS (40-60 lbs)
90 lbs of LR
5 small fish
2 anenomes
30-40 gallon sump/fuge

I have to use an overflow box which will be a Sealife System 60/100 single output with a Mag 12. Also i will have 3-4 PH in the tank itself.
My questions are:
1) will the mag 12 overpower the overflow? Do I need a ball valve(Im going to install one but will I need to use it?)
2) Are there any instructions out there showing or detailing how to use the overflow box? I know you fill the sump top where you want the water level to be, then fill the tank to the edge of the overflow box, but dont know what to do after that. I know you have to put the airline tube into the Utube to get the air out...anything else?
3) Are overflow boxes relaible as long as air doesnt get in the Utube?
4) How far from the wall to people set their tanks? Didnt think this through on my first tank and set it to close...

Im transferring all of the above from a leaking tank so this is the task at hand. Any and all suggestions are appreciated.
Im sorry but i dont reconize the sealife system 60/100 overflow. What size output does the overflow have and what size U tube? Most single outlet overflows are rated for 600-700GPH max. That mag 12 will push a whole lot more than that unless your talking about having a head height of 8'-10'.

The following link has some very good info on the specs of the Mag pumps.

You have two parts of the overflow. The inside and outside parts. The inside usually has an adjustment to control the water level in the tank. Start with this all the way down and rase it slowly as the system is running till you have the desired water height. you insert a bit of airline tube in the U tube till its at the top of the peak. With water in both the inside and outside chambers you suck the air out of the U tube. Once all the air is out of the U tube you keep the U tube submerged as you pull the airline out. the overflow is now primed. You would have already plumbed your drain and return lines at this point. Then you power up the pump and watch and make sure things start up like they should.

As long as you keep the U tube clean of algae and do regular maintance on the overflow prefilter if one exists the U tube overflows are very relyable. I have only had them fail when regular maintance was avoided.

First how thick is the outside part of the overflow. Then add a few inches at a minimum. The distance is up to you but you need to allow enough room to reach in behind the tank do to work if you need to.
I have a 2 1" dia U-tubes with 2 Gen-x 4100 and it is just enough. Not too much, but just enough. Also, as stated above Head height is a big factor. My pumps are rated 1000gph plus each, but at 5' (distance from bottom of sump to the top of my tank) they are only producing around 650 gph each.

Best thing is to fire it up and stand right there ready to unplug if needed. :)

Also regarding failsafes- test test test. Simulate a powerloss and more important a power resume without touching anything on the tank and see what happens. Lots of overflows are ok when they lose power (because the pump stopped also) but when they kick back on, if the syphon is gone your going to have trouble.

The U-Tubes my LFS stocks have a baffle on the back side to keep the tube submerged even when the flow/pump stops.

The output (tube size) is 1". I assume the Utube is the same. Also I will have about 5-7 ft of head height. Im going to "hard plumb (PVC)" in the return line as well as the drain into the sump. Going to have a 1" drain as well. The sealife System 60/100 is good for a 60 gallon or 100 gallon tank. After further review, it will handle about 800GPH so I will have to throttle the mag a bit.
However will this idea work....What if I added sort of a "S" in the plumbing up to the return so i dont have to throttle the mag as much? I could feasibly add 3-5 more feet of head height or plumbing to the equation..
What would happen if I got another U-tube? Would this help?
If the Mag 12 is 1200gph and you have 5' or more of head height there is a good chance that your actual flow is < 800 gph, so you might be fine.

Turn it on and watch - as long as you keep one hand on the plug you can remove it before things get soaked.

If you did want to add head length, or use a smaller dia tube that would reduce flow even further.
So are you saying reduce the 1" return line to 3/4"? I think I had rather add more PVS line to add head height...seems the simplest since I have already bought the PVC.
Any and all suggestions are welcome. I want to set this up right the first time!
Re: return line - if you mean the line up from the tank - yes.

Increasing the head height or line length or shrinking dia of the line UP to the tank FROM the sump will reduce flow.

To increase capacity of the overflow - the piece that counts is the U-tube - bigger is better.
Head height is mostly calculated by gravity. If you have horizonal or an S where you have runs that acutally go back down this wont slow the flow much.
So should I reduce the diameter of the return line then? What are my options then if I want to reduce the flow? I am going to get a ball valve in line but would rather not use this if I can help it. Tell me what you think I need to do...
A ball valve would give you adjustability that reducing the diamater of the return will not. In addition dropping the diamater of the return will reduce flow somewhat but also increase the force of the water comming out of the return. Think about a garden hose that is on full and you then take your thumb over half of the outlet. Overall the flow may be lower but its got alot more force comming out.

Either method your increasing the head pressure artifically. Another thing you can do that will not adversly affect the pump. is to split your return. Put a ball valve on the line running up to your tank and have a second leg below this ball valve that dumps back into the sump. This will allow the pump to run at full flow and have a minimum level of back pressure.
So basically add a second return line and below the ball valve and have 2 returns instead of one?? This wont overload the main tank I assume as the drain going to the sump will only be one instead of 2? If this is so, kudos to you!!! Just want to make sure I dont overdo it on the return.
no no no.

From the pump have a single line. Then split this off with a T connector. Position the T so the stright thru part is going up and the leg going off to the side is either to the left or right of the pump. What ever way you have more of the sump. Above the T put a ball valve to control flow to the main tank return. Also put a ball valve on the side leg of the T. Then plumb the side leg of the T to dump directly back INTO the sump.

You only have 1 line going up to the tank and the rest of the water that the pump is pumping just circulates back into the sump.
Ok I see...BUT would it not work to have 2 return lines back up to the tank? Take your same setup and instead of running the t side back into the sump, run it to the other end of the other words have 1 return at one end of the tank and one at the other.
I do see what your saying now. I just thought it would be nice to have 2 returns for more circulation. But I do see it might overload the f I do it the way you are saying, it will not overload the sump?
Thanks again for all the help!
Sure you can have two return dumps in the tank but take that single feed going up above the ball valve and split it again. If you dont have a 'bleeder' line dumping back into the sump you will have to throttle back that pump a fair amount causing excessive heat and wear on the pump. No mater how many outlets you have if you dont have a bleeder your still putting more water in the tank than your overflow will remove.
Got it...ok so I can have 2 return lines to the main tank and then one bleeder back into the sump. BUT I will have 2 T's in the equation, 1 ball valve, 1 bleeder back into the sump, and 2 return lines. So basically come out of the pump into a T, the straight part going up towards the tank and the bleeder heading back into the sump. The install a ball valve above the 1st T, the above the ball valve have another T, with one going to one side of the tank and another to the opposite side of the tank. I think this is it...Thanks for the help and let me know if Im still missing something..
I belive if you read up I suggest at least two ball valves. One on the bleader feed and one on the return line. Its hard to have to many ball valves.
Top Bottom