Stupid Question, overflows, siphon breaks, etc...

[rovster]

I have what is probably a stupid question, but I will ask anyway because its been confusing the heck out of me. I've been researching overflows and sumps and drains, and all sorts of plumbing for my upcoming build, and one thing that is confusing me is the "siphon breaks" and how much importance is placed on them from a safety/flood perspective.

I am assuming that this siphon break is to prevent your sump from overflowing. I can see that if you get a full siphon on your drain, the water would definitely come out of there VERY quickly, and your retrun would get overwhelmed rather quickly. You cannot get a siphon coming from the return because gravity is a *****. All that said, when you first fill your tank and sump, your sump full should match your "completely drained DT" level, so assuming you sump did get overwhelmed, your drain hight would eventually break siphon and the system would self correct? So I guess there is not risk of flood or anything catastrophic.

So, I ASSume that the siphon break is to just prevent this near catastrophic experience from happening or starting to happen over and over, correct? Sorry for the long post and I hope I explained myself well. Any comments on purpose and location and the "why" of siphon breaks would be appreciated. A dumb newb would appreciate it:hmm5:

 

[daplatapus]

Disclaimer: I'm fairly new at this and the answer below is based on how I have my tank set up and my understanding of hydraulics. Any correction and/or clarification would be awesome for my education as well.

Siphon breaks are insurance for when the power goes out. In your DT you have drains and returns. Both have the possibility to turn into full siphon drains in the event of a power outage. Your drains will just drain the water inside your tank up to their respective heights. In many cases that will be to the bottom of your teeth of the overflow. Water inside the return lines however, will naturally "fall" back into your sump when the pump shuts off creating a siphon in the return line. So if your return line discharge is 12" down from the surface of the DT level, it will suck the tank down to that level, when it will then start to suck air, thus breaking the siphon. It will only drain the DT to the level of your lowest port, be that the drain or the return. Drilling siphon breaks in your return lines (or making sure your return lines end above the level of your overflow teeth) reduces the water level at which it will start drawing air and break the siphon. The important part of setting up your sump is ensuring that it can handle that volume when the power does go out.

 

[cincyjim]

I seen on you-tube where a guy drill a very small hole in his return line about a inch-inch and a half below the water line. This way if the power goes out the siphon would be broken at that position. It looked like a good idea but I have never tried it.

 

[jcw]

siphon breaks prevent water from siphoning backwards through the return back into the sump.

however, small holes are easily plugged with algae and fail so the best bet is to position your return close to the water surface so when the back siphon does occur, it will only take down a smaller amount of water before the return is above water and it still won't overflow the sump.

So on a properly designed system with plenty of sump room and properly placed return lines, you should not need siphon breaks.

 

[Meshmez]

as stated above, a siphon break should be a safety mechanism above and beyond making sure your sump can take the full amount that "could" be siphoned.

It will drain the DT to the lowest port ON THE TUBE DOING THE SIPHONING. if you have a drain 2 inches below your water level, but your return line is 12 inches below your water level, with no siphon break it will drain your DT to 12 inches below the water level. your best bet is to make your returns as high as possible, and make sure your sump can handle all the different pump failures possible (all power off, one pump failing, 2 pumps failing, depending on your setup and plumbing system.) and im taking handle all the water with room to spare, not "well it was right on the edge of the sump.."

THEN add siphon breaks (because draining less into your sump is still better if possible)

 

[BUBBLE MAN]

the wet/dry filter i ordered from foster & smith came with a pre-drilled siphon break on the return nozzle.

now, what would be the best way to determine your "power outage" sump water line?
fill the tank, start the siphon, start the return pump, let it run for a bit, then kill the power and mark the line on the sump?

 

[Reefermandan]

I put 3 holes in each of my 3 returns right below the water level (1 more then most people but I wanted to be sure). I can't imagine all 3 getting plugged but I guess it could happen. I end up testing ever time I feed though because I have my Apex shut down return pump, skimmer and all powerheads. With the 3 holes in each return it also ends up moving around the top of the water column a little bit which I think helps.

 

[Hal]

Even if you have a siphon break, make sure your sump can handle the volume of backflow as if your siphon break didn't work.

 

[Meshmez]

the wet/dry filter i ordered from foster & smith came with a pre-drilled siphon break on the return nozzle.

now, what would be the best way to determine your "power outage" sump water line?
fill the tank, start the siphon, start the return pump, let it run for a bit, then kill the power and mark the line on the sump?

yes, have your tank running as normal, and then kill ALL the pumps. This includes skimmers and filters which can actually hold quite a bit of water. when testing be ready to flip power back on if it gets too close to overflowing (and then go buy a bigger sump...)

 

[BUBBLE MAN]

yes, have your tank running as normal, and then kill ALL the pumps. This includes skimmers and filters which can actually hold quite a bit of water. when testing be ready to flip power back on if it gets too close to overflowing (and then go buy a bigger sump...)

gotcha. awesome. thanks. :wave:

 

[rovster]

Got it thanks. Most of the setups I've seen have the returns near the surface so I didn't even consider that. I think I got it.