Mechanics of Overflows, Predrilled Tanks, and Sumps

[subliminalanarchy]

Okay so it's my understanding that in order to use a sump there is 2 main ways to get the water down into it:

1) An overflow that operates by a siphon.
2) Having a hole drilled in the side of your tank so the water just falls into the sump by gravity.

An overflow sounds like a bad idea to me because if the power goes out, then the siphon would break and then when the power comes back on, the return pump would just start back up and the top of your DT would just overflow, right?

So because of this my natural choice would be to get a drilled tank, but everytime I google it I find that people use overflows even if they have a drilled tank which seems to defeat the purpose. Very Confusing. Why can't you just drill the top of your tank and put a screen on it so the water just overflows into it?

Also I've seen that alot of predrilled tanks are drilled on the bottom. This makes sense because then the plumbing can stay in the stand, BUT, then I don't understand how you would keep sand and other junk from falling right into the hole without clogging up the screen?


Can anyone enlighten me? Thanks!
I couldn't find any good information on this believe it or not

 

[scottayy]

I just set up a sump that operates by siphon. If you keep the water in your return compartment low enough to handle the drainage from the return tubes, it will not flood the sump should the power go out. If the siphon breaks, there should be enough space for water (probably a gallon or two) in your DT to handle all of the water that the pump can pump up to it. I managed to get my water levels correct in about 30 minutes. Just takes a watchful eye and readyness to correct a flood before it occurs.

I don't want to say I'm flood proof (because then I would surely have a flood), but I think I am.

Also, drilling holes in the return lines, just beneath the surface of the water line, stops water from back siphoning into the sump through the return lines.

Regarding overflow box with drilled setup - I'm not SURE, but I have an idea. It skims the surface of your water and prevents a film from being there and it helps aerate the water by promoting gas exchange during the water fall into the overflow box.

As far as holes on the bottom.. I don't know!

 

[subliminalanarchy]

Thanks for the help. I didn't know about putting a hole in the return line to prevent a back siphon, I'll try to remember that.


This whole things confusing. I'd swear the hardest part of this hobby is the plumbing.

What's funny is that I don't even have a set up yet. I probably won't have a reef tank for a few more years actually lol. I'm way ahead of myself here, I just like to be prepared.

 

[scottayy]

This whole things confusing. I'd swear the hardest part of this hobby is the plumbing.

Trust me, I know, lol. If you read through my thread "my FINAL sump thread", you'll see my build and various issues I encountered which may help you think ahead a little bit.

Good luck!

 

[subliminalanarchy]

Just read through it

 

[Smitty]

The tanks with the holes drilled on the bottom are called "reef ready" tanks as most reef tanks run a sump. The holes are typically drilled close together and then they are separated from the main tank by a wall(s) of Plexiglas/acrylic or something (one hole is the drain, the other is the return). This is also an overflow location. The water from the tank will flow over the top of the tank and into this section for the drain.

A HOB (hang on back) overflow is usually designed so that when the power goes out you still have water in the tube going over the rim of the tank as the water in the intake section inside the tank never goes empty and there are 2 section of the intake section outside the tank. The tube stays submerged the entire time so it never looses the water inside. You can get air bubbles inside that tube though, which can be a pain to work with.

Both methods (if done properly) are pretty reliable. Many people like the reef ready tanks because you don't have to leave room behind them for the overflow so they can be much closer to a wall.

 

[carey]

I solved my overflow box problem by getting a continuous overflow box. It has an air pump that constantly removes the air so the siphon stays strong.

If the power goes out the siphon stops and the sump fills up with whats left in the tubes and whatever your return nozzle will allow back in. If you don't drill that hole in the return nozzle you will siphon back into your overflow and flood.

It does take a bit of tweaking but it's def possible. i am a total tard when it comes to this stuff but I got mine working.

 

[Firemedic1081]

I currently have a 75 with a HOB overflow. I am working on setting up my new 125 and I am going to drill it. The holes in the back glass will have a bulkhead fitting with a strainer. No overflow box. The thing to think about when not using an overflow box is the volume of water that you plan to pump through your sump. You need to not only be able to take out the volume of water that you pump into the DT but also need to have plan for a blockage. If a snail or some algae blocks your overflow, you need to still be able to handle the volume of water coming in. Adding more than 1 overflow should allow this. I figured that I need two 1" overflows to handle my return pump so I am using three. If one becomes blocked, the other two can still maintain the gallons per hour that I need. Also keep in mind that just because you can get X number of GPH through a pipe does not mean that you should. The more full that the pipe is, the louder that the gurgling will be. You want the pipe less than half full. Ideally a third full or less. And to finally get to your question.... The overflow box is another way to get water into the pipe quietly. It also allows you to get a thinner "sheet" of water off of the surface which makes the skimming effect more efficient. Do a search for "aquarium overflow calculator". I think it's Reef Central that has a good one. It gives you the linear feet of overflow required. That is the total length of the top of your overflow box or overflow pipes in my case.

 

[subliminalanarchy]

Wow a bunch of good information there guys. I think I pretty much get it now. I suppose I'll actually have to set one up before everything will totally register but I've got a better picture of how it works now. Thanks