What stops sump from flooding?

[Debbie G]

I am now at the phase where I will start figuring out how to connect all the plumbing, etc. for my new tank. I'm pretty confounded about this part. Everyone is saying to make sure there is room in the sump to allow for a power outage and that the sump is big enough to hold the water in case the display tank starts to drain. But clearly, the sump is much smaller than the display. Here are the stats...the tank is 175 gallons, the sump is 30 gallons.
If I only keep the sump filled with 20 gallons of water, is that enough room to allow for some draining? I don't get the physics of this. Then I see everyone talking about the gph of the pump related to the overflows (my tank was not reef-ready).
How do I figure out if the pump is going to be too powerful/not powerful enough for the amount of overflows I have? I don't even remember how many gph the overflows are supposed to handle (I bought them a year ago and God forbid it should tell you on the box ) Each one measures 10" x 5-3/4" x 4-1/4" and there are three of them. Does anyone know how many gph they would handle by looking at the measurements? My water pump is an Iwaki MD 100 rlt. If someone can help me figure out the math on this, I'd TRULY appreciate it. Then I could go on to my next 1000 questions :lol:

Thank you so much, I appreciate the help from you all tremendously.
Debbie G

 

[hdtran]

No math needed, just a few simple tests (iteratively).

You simulate a power failure by unplugging your pump, and see how much water overflows into your sump without flooding. That marks the maximum level of water in your display tank.

Then, you simulate an overflow failure by putting a snail or snail-like object in your overflow, and see how much water from the sump is pumped into the main tank (without flooding). This sets the maximum water level in the sump.

Use a magic marker to mark both display and sump, and repeat tests above until no water is on the floor. (Actually, you don't let water flow out on the floor, but hopefully, this post makes sense).

 

[Anonymous]

Hi Debbie,
Ditto what hdtran says. Also, so that you don't do a reverse siphon on your return to the main display tank during a power outage, put a small hole in the return hose just above your water line in the display tank on the return itself. That way when the pressure stops, you allow air to enter the return, so that you don't drain your tank into your smaller sump. Then the water level should go down only to your overflow "box" level. As an example, I have my hole pointed towards the back and down, so that it's not squirting up/out/all over the place.
I did this and it works like a charm for me. I live in a second story condo, so any water on the floor creates very unhappy bottom-floor-dwelling neighbors. 8O
HTHs,
~wings~

 

[Anonymous]

Good responses, but I think he want's to know "why" the sump will not flood. The reason is that the water in the main tank will only drain down to the level of the overflows. OR, the level of the lowest syphon tube.
You need to make sure your sump can handle this amount of water.

Jim

 

[Anonymous]

Yep. That's why sumps look like they need to be filled up a little more. That's the extra space to hold the extra water from the main tank, in event of a problem.

Basically, what you do is make sure that the hose or intake in your main tank (leading down to the sump) doesn't go too far below the water line in your main aquarium. If it does, this means more water can siphon out.

Also, it's a good idea to set your system up w/ fresh water and simulate a pump failure (turn off your return pump) ... watch the overflow keep siphoning, watch your sump fill and then watch the siphon break at the appropriate time. It's a lot of hassle, but it's gotta be wayyyy better than finding out the hard way that you didn't calculate the sump volume correctly and that a lot more water siphoned out during the power outage than the sump could handle

 

[jwc3]

How do I figure out if the pump is going to be too powerful/not powerful enough for the amount of overflows I have?

Can someone answer this part of the question? I'd like to know how to figure-out the correct size pump, too.

 

[Anonymous]

Or, if you DO have a hose or pipe that goes a ways below the water line (one of mine is on the bottom) make sure you drill a hole in the pipe just below the waterline. This will break the syphon should the power go out. Just make sure that cleaning this hole is part of your maintenece routine.

Jim

 

[hdtran]

How do I figure out if the pump is going to be too powerful/not powerful enough for the amount of overflows I have?

Can someone answer this part of the question? I'd like to know how to figure-out the correct size pump, too.

To first order, it's self-balancing. If your pump is too feeble, the overflow flows down until it gets near the bottom of the grate, and the flow reduces automatically until the amount of water coming in is equal to the amount of water the pump shoves out. If the pump is excessively strong (almost impossible, by the way), the amount of water in the display goes up, causing more flow through the overflow grate. If your pump is excessively oversized (think a 5000 gph pond pump on an overflow with a 1/8" tube and a 1" wide box), the pump pumps water out of the sump until it's blowing half-water, half-air--basically limited by water coming in (again).

 

[Debbie G]

I can't believe it, but I actually understand what you guys said!
It all makes sense! I thought I was going to have to take a math course!
I cannot tell you how much your responses mean to me, I don't feel so dumb now! :wink:
I'll have this thread printed up and sitting next to me when I do this.
And again, I appreciate the time you took to explain it to me.
Gratefully yours,
Debbie G

 

[mountainbiker619]

How do I figure out if the pump is going to be too powerful/not powerful enough for the amount of overflows I have?

Can someone answer this part of the question? I'd like to know how to figure-out the correct size pump, too.

What I like to do is make sure I get a pump that is big enough and use a gate valve on the return side of the pump to manually adjust to the correct flow.

 

[insearch]

What is the rule of thumb here. Is it 10 times tank capacity per hour?

 

[MI0706]

insearch: From my understanding, 10x is usually a good number to start with. But I believe I have heard of people going up to 20x. I think it mainly depends upon what you are going to stock in the tank.

IT SEEMS LIKE EVERYTHING BOILS DOWN TO WHAT IS GOING TO BE STOCKED IN THE TANK... Lighting, flow, etc...

Some of the more experienced guys here can correct me if I'm wrong.

 

[Anonymous]

Flow in through the sump is different then flow in the tank. You don't need to move 20x through the sump.

Does that make sense? Sorry, I am in a rush right now! :mrgreen:

 

[ADS]

You can also buy 1 way back siphon valves in 3/4 & 1 ".
Adam

 

[Anonymous]

Check valves are notorious for failing just when you need them not to. I would not count on them if I wanted to sleep well at night.

 

[ADS]

There are cheap versions of everything. There are commercial grade check valves that would prevent back siphon consistently. Aquatic ecosystems sells them.

I agree that knowing your maximum water level in tank & sump is the best way to prevent flooding. Adjusting inflow tubing to the tank level is key and the hole in the inflow at water level breaks the siphon.
Adam

 

[Anonymous]

Which ones? I have never seen nor heard of a check valve of any kind that was 100% reliable in an application that involved organics, as the organics can easily inhibit the function of flaps and springs and plungers. But, I would be thrilled to see such a thing!

BTW, I do run two 1 inch true union swing check valves on my system, but it they don't work the sump handles the back flow.

 

[Insider]

Why dont you use a continous siphon overflow setup from display to sump? The ones that stops when your pump stops and automatically continues when pump restarts... they can never overflow your sump. One way check valve or a stop reverse siphon hole in the return to diaplay path.... these are fool proof setups that I use.

 

[Baianotang]

The overflow box (?)

 

[Anonymous]

It is important to note that no system is foolproof - they all have their dangers.
A siphon overflow may not overflow your sump, but if the siphon breaks or gets restricted by refuse or bubbles you tank will over flow.
I like redundancy, so I try to incorporate many things - my pumps are on float switches, the sump can handle the volume, siphon break holes and checkvalves.