Flood prevention when power goes out?

[SirFragalot]

I'm in the process of plumbing my tank and have a question....or twelve.

With this being my first time actually plumbing a tank myself (i'm trying not to be lazy on this tank and take a little more pride in it), I was wondering if there was a way to prevent the water from flowing back down into the sump when the electricity goes out. When this happens, does the water flow back down till it reaches the level of the return line? Or the overflow? Or both? Is there an automatic valve that can be put in place to prevent water from draining down the return line to the sump? Or is it pointless and the water will flow down till the water line reaches the overflow drain?

 

[kschweer]

There are a few methods to help reduce the amount of water going back to the sump when the power is out. First is a check valve. This is a one way valve that will let water flow through but not back. Second is a siphon break which is a small hole drilled into the underside of the 90 that your locline threads into which allows air in to break the siphon that is caused when the power goes out. Third is setting your return so that it is just under the surface if the water so that when the power goes out the water will only flow back until the return draws air and breaks the siphon.

I would first figure out how much free board or room in the sump for excess water you have. There are drawbacks to both the check valves and siphon breaks. Both will need some maintenance. Check valves can get dirty and not work properly and can also break so you need to keep an eye on them. The siphon break hole can become clogged with either debris or salt creep and also should be watched closely. On my tank I do not run a check valve or siphon break. I made sure that my sump had enough free board and that my return was just slightly under the running water level. You can easily calculate how much water will be siphoned back through your return by multiplying the length time the width times how far your return is under the water and dividing by 231. Length x width x depth divided by 231. All measurements in inches. You will then know if you have enough room for the water in your sump

 

[adesimone1]

Well there is a couple things you can do.
Make sure there is a siphon hole in your return line. Keep your returns close to the top of the water level in the tank. If you are using a sump keep your baffles lower so when your tank does shut down it will be able to hold the extra water that will back low to the sump. You can also put a check valve in your return line.

 

[redfishbluefish]

I originally installed siphon breaks (and they’re still there), but eventually installed a total of four loc-lines so my return flow wasn’t too great. This allowed me to raise the Loc-line so it was just at the surface of the water. Now I get no back-siphoning from my return lines. I only get water free-flowing down the overflow until it gets to the bottom of the saw-teeth.

And, if you’re interested, here’s my siphon break. It’s a threaded coupling that I drilled and then glued (epoxy) a short piece of tubing (same stuff on our RO units). The tubing just goes below the waterline. This way I don’t hear that tinkling of water.

 

[SirFragalot]

Thanks for all the suggestions. I was well aware about making sure there is enough room in the sump. My problem is that the Bubble Magus NAC6 skimmer suggests a 9 1/2 to 11" water line for optimal performance. The 20L is only 12" high so I was going to use the minimum 9 1/2". I'm thinking of going with a 29 that's the same length and width but 18" high.

 

[redfishbluefish]

I’m in a 40B with relatively high baffles and still have room for the back-flow from the DT:

When I turn off my pump, the water level fills the return section just to the level of the baffles.


You can easily calculate the volume of your backflow and the available space in your sump. Use the tank volume calculator on RC and put in the appropriate measurements.

 

[SirFragalot]

See.... This is what I get for not doing anything myself on the last system. I didn't learn much when it comes to that stuff. LOL

 

[lefkonj]

I would also say make sure you use unions and valves on the drains. This way you can easily work on things and tune it right. My 180 has two drains, one is open 100% the other about 75%. That has been the best balance for returning/draining water in my system. When i turn everything off the drains drop several inches of water into my sump but not enough to overflow.