More overflow/sump questions

[beattyr]

Guys,
Working out the logistics of my sump system I am building. I have a question though. How do I keep the overflow from breaking suction if I am making a hang on style overflow? Eventually air will build up in the overflow elbow and break the suction correct?
Suggestions?
Also how can I balance my input to the sump with the output flow from the pump?
Thanks
Rob

 

[kandr]

Originally posted by beattyr
Guys,
Also how can I balance my input to the sump with the output flow from the pump?
Rob
I was just about to start a thread asking this same question. My
DYI sump is almost at completion. I've been going over the
circulation of the sump water in my head, and I can't figure out
how I'm going to get a complete balance from the pump and the
siphon.
One possibility that I have come up with is to place a PCV tee
adapter in line to the drip plat, located above the water in the
sump. In this tee would be some sort of valve that limits the
water flow as the water level in the sump is raised, thus alowing
the pump to catch up. I've added an illustration.
Please let me know what you think.

 

[broomer5]

As long as the overflow can handle the maximum water flow that the pump pushes up to the display tank - there is no balancing required.
If you fill up a five gallon bucket of water to the rim, and stop just before it overflows - this is like a display tank filled all the way up to "just" where the overflow teeth are located.
You add 1 cup of water to bucket - and just one cup will overflow it's rim and run down the sides.
You add just one gallon to the display tank and just one gallon will "overflow" through the teeth of the overflow and drain to the sump.
What goes up will come down - same amount - no balancing.
500 gph up - 500 gph down - 500 gph around and around.
If the overflow is underated for the return pump, say it's rated for 700 gph, but you pump 800 gph with the pump - you will overflow the tank's side edges and water will run over the sides to the floor.
The sump will then go dry, and pump may burn up.
There's no need to balance anything in a single sump, with overflows that lead to it - if the return pump is in this same sump.
Some people will install a ball valve on the discharge of the return pump so they can tweek or adjust the flow to the display tank.

 

[kandr]

That does explain a lot. This will save me a lot of time and trouble.
But this brings up another concern.
If the siphon breaks while I am not home, the water in the sump will overflow into the tank. And as a result, this may cause the pump to burn out. If this is correct, is there some sort of cut off switch for the pump? Or am I missing something. Again…
I'm not worried so much about the water overflowing out of my display tank. The pump sits in a separate small reservoir at one end of the sump, so not much water would pump up.

 

[newfishliny]

there is something called a thermal cutoff-
when water stops going threw a pump this prevents the motor
from burning out. You would have to check diff manufactor if they have this. I know on pool pumps and sump pumps its on it.
good luck

 

[broomer5]

beattyr
Sorry I did not address your original question.
Most folks purchase a well designed external U tube or similar type overflow. Not that it's impossible to DIY, just that there are several key design factors that must be followed.
If you're building your own overflow, I suggest you either look at a "good" one and copy some of it's features, or look on the internet for DIY designs and follow them.
If it's built right, then about the only way for it to fail is as you mentioned - air becoming entrapped in the U tube and causing the siphon to break.
The way around this is to make sure you have enough return pump flow up to your tank. Having enough flow up to the tank will allow the water to rise enough up in the tank, to a level high enough as it falls into the inner box, it will be doing so at such a rate, that the velocity in the U tube will be high enough to carry any entrapped air bubbles right on through the U tube to the outer box.
Too little flow up to the tank will only allow a slight trickle through the teeth of the overflow inner box - and a very very slow rate through the U tube. Not enough "grunt" to move the air bubbles on through and out the other end of the tube.
The other thing that affects this rate of flow through the U tuge, is the square surface area of the tank. I've been struggling with this idea for awhile now - but I do feel that it affects the rate at which the water moves through the U tube.
Given the same size U tube/external overflow - the larger the tank's surface area - the slower the flowrate.
If you want more info in making the DIY overflow - ask.

 

[reeflooker]

Consider using two or three syphon tupes. If you lose suction in one, the others should work fine.
I would strongly suggest you get a predrilled aquarium. Don't fool with the overflow boxes. You will be glad you did!!!!!!!!!!!

 

[broomer5]

reeflooker
I agree 100% on the predrilled tank advise.
By far the best way to go.
I disagree on putting more than 1 U tube in a single external overflow though - IF the concern is air entrapment.
If the return pump is so weak in comparison to the desigh flow of the overflow - you have slow flow through the U tube - and air bubbles will form in the top of the curve - accumulate and cause loss of siphon.
Placing another U tube in there, or a third, if all of equal size and shape, will only compound the problem, splitting the flowrate into thirds, each one taking 1/3 of the total flow.
Ideally - replacing the return pump with one that is better matched for the single U tube overflow is a better choice in my opinion.
At least for the low flow air entrapment concern.
A drilled tank eliminates the need for this conversation.