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markhilken
12/02/2008, 01:20 AM
Hello everybody, anybody ever use check valves(1 way regulated water flow) in the return lines going into the dt from the sump? I have seen posts here on this forum where there is a power outage and return pumps fail and water siphons back into the sump from display tank. Wouldn't a check valve prevent this?
thanks

kdblove_99
12/02/2008, 01:45 AM
yes they will but it is just a matter of when that check valve will fail. They all fail!

Toddrtrex
12/02/2008, 02:12 AM
Yep, they will fail.

I have one on my 29 (( really don't need it, since my return line is high enough that my sump doesn't overflow -- but I was short on some pipe and had it laying around )). Each time I shut off the main pump I can hear it failing, the water keeps going into my sump until the water level in the main tank is lower then the return line.

Having the return line high enough ( and a big enough sump ) is really the only way not to have a flood.

markhilken
12/02/2008, 06:29 AM
Thanks for all the replies

dkh0331
12/02/2008, 06:56 AM
You can drill a couple of anti-siphon holes into your return line. Just below the water line, drill a couple of small holes. This will stop the siphon. Just make sure that you take a toothpick or similar device and keep the holes clean when you change water/clean your tank.

AZDesertRat
12/02/2008, 07:28 AM
Never rely on check valves or drilled holes, both are a recipe for disaster.
The only fool proof method of backflow prevention is an air gap. Keep your returns just under the surface of the water so when the power goes off only a slight easily calculated amout of water returns to the sump. Always maintain that amount of freeboard or space in the sump and you will never have a problem, best of all you can sleep at night not worrying about it.
Holes get plugged and require constant maintenance but even then a snail can park over them, or an anemone, fish, food, algae etc. same with a check valve, it does not have to be a catastrophic failure, a single grain of sand on the valve seat can drain a tank in a matter of minutes. No amount of cleaning and maintenance can prevent it.
My 100G display siphons a maximum of 3.8 gallons back to the sump in a power outage. I always keep 5-8 gallons of spare room in the sump even when topped off so I don't worry about floods.