Check valves

[em805]

Hopefully I used the correct terminology... Does anyone know what the best way to prevent backflow into your sump via your return pump plumbing during power outages? Maybe a check valve (please correct me if that is not the right term) I could install on the line that goes from the return pump to the tank. The hose from my return pump to the main tank is 3/4", I know they make similar mechanisms for the 1/4" r/o tubing. Thank you, and I appologize if I used the wrong terminology.

 

[AZDesertRat]

Check valves are not a good option, they can and will fail at the worst possible moment. Thats Murphys Law at work. They are a mechanical device even though they are simple.
Your best bet is to have the returns and overflow high enough in the tank that only a small amount ofwater backflows. You should always reserve enough room in your sump to contain this amount of water, I repeat always keep that much freeboard, thats very important. If you don't you will have a flood.
Also for a little extra safety you cab drill a couple of small air break holes in the returns just below the water level so once the holes are exposed it sucks air and breaks suction stopping the flow of water. This is another iffy thing though because you need to do regular cleaning of the holes and keep snails and algae away of they will plug and do you no good.
So the best method is a large enough sump to contain any backlfow that may occur worst case and to have the returns and overflow high up in the display.

 

[em805]

check valves

check valves

Thanks again for the info. Up till now I haven't had an accident, but I beleive in prevention, besides after reading some of the disasters on this site from water damage it's hard not to take some preventive action. My tank was predrilled with a return, so I find it very difficult to move the return line--other than re routing it through the drain section. I have a corner tank with a pre-made overflow box... Perhaps, cutting a hole on the overflow box lid and running the line over the top of the tank and placing it closer to the surface? I could even an oscillating wave mechanism at that point... Don't know if those instruments lend themselves to corner tank set-ups, do they?

 

[AZDesertRat]

Where is the return located? Is it drilled in the back or the bottom? I have both my overflow and return lines inside the overflow box with the return plumbed above the surface and then split into wye with two 3/4" LocLines extending from there. I always make sure the loclines are no deeper in the water than the bottom of the fingers or notches on the oveflow box so water never goes any lower than that point when power goes off.
My sump is then filled and I operate the system for a minute then pull the plug to see how high that raises the level in the sump. The sump is them marked with a permanent marker with both the power off high water level and the tank full and operating water level. I never fill the sump above that point ever.