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I have my airpump below the water level and unplug it constantly, and it stays off most of the time. The water does siphon out but only up to the water level (the water rises if I push more of the tube underwater and vice versa). Do I need a check valve?
 

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Fish keeper,

I would say yes you need a check valve. They are cheap and can save you from a electrical fire. If water is siphoning back into the tube it could eventually lead back into the pump and one day you'll plug it in and "BAM" an electrical fire and you could get hurt. Save yourself the stress and insure your home and family with a 2 - 3 dollar check valve. Be safe.
 

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If the hose goes up over the edge of the tank and then down to the stone/bubbler then the water cannot go higher than the waterline without some suction to draw it up and it would have to draw it over the highest point of the hose for it to flow down to the pump. It is quite normal for the water in the hose to rise to the level that you mention.

Checkvalve if you want, not needed though.

Jeff.
 

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Oh the air pump isn't even connected right now, I have been planning to use it for something else for a while, and I'll make sure the air pump is above the water. I was more thinking for future reference, thanks, I'll get it next time I need it. For now I'll make sure the end of the tube is above the water line so it doesn't flood everywhere.

Do you know why the siphon water in the tube always seems to want to match the water level?
 

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Oh the air pump isn't even connected right now, I have been planning to use it for something else for a while, and I'll make sure the air pump is above the water. I was more thinking for future reference, thanks, I'll get it next time I need it. For now I'll make sure the end of the tube is above the water line so it doesn't flood everywhere.

Do you know why the siphon water in the tube always seems to want to match the water level?
The same reason that water in a glass is always level. if allowed to flow freely water will always flow to equalize the level throughout the volume even if it is connected by a hose. If you take a long siphon hose and fill it with water and raise the end of the hose, no matter how long it is or how large or small the diameter, the level of the water will always be the same level as the tank level.

Great tool if you are building a deck and don't have a long level to get the support posts all to the same height.

Jeff.
 

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Discussion Starter #6
The same reason that water in a glass is always level. if allowed to flow freely water will always flow to equalize the level throughout the volume even if it is connected by a hose. If you take a long siphon hose and fill it with water and raise the end of the hose, no matter how long it is or how large or small the diameter, the level of the water will always be the same level as the tank level.

Great tool if you are building a deck and don't have a long level to get the support posts all to the same height.

Jeff.
Then why do we need check valves if water always strives to equilize?
 

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Then why do we need check valves if water always strives to equilize?
You don't unless the water actually goes over the side of the tank in the hose to a canister filter perhaps... but even then just a shut off is fine to keep the water in the hose while the canister is disconnected.

If everyone uses them, maybe it's just in case they accidentally suck on the air hose which would be a water problem... but I can't see that happening.

Do air pumps reverse sometimes?

Jeff.
 

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I have my airpump below the water level and unplug it constantly, and it stays off most of the time. The water does siphon out but only up to the water level (the water rises if I push more of the tube underwater and vice versa). Do I need a check valve?

My answer to needing a check valve for the air pump below the waterline that is unplugged constantly is accurate. You dont need a cehck valve for a DIY CO2 system or for an airpump that is above the water line because in a DIY CO2 system there are no electrics and the system is usually sealed tight. In a pump that is above the water line the water will not rise up into the pump. Gravity and equilibruim is at work here.

I dont see why you wouldnt use a check valve in any case though for a pump either below or above the water line. Its safe, it cost 2 maybe 3 dollars and what happens if someone/something knocks the pump onto the floor when its not plugged in? A simple 2 maybe 3 dollar tool can save you hundereds of dollars. Its safety verses possibilities.
 

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For what it's worth every pump I've ever bought comes with a check valve and a manufacturers recommendation to use it if the pump will sit below the water line.
Although starting a siphon may be unlikely, it's just a precaution against potential damage or shock. Much like using a GFIC (ground fault interrupter circuit) for lights, heaters and such.
I think they sell them at wallymart in two packs for a couple of dollars.
 
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My answer to needing a check valve for the air pump below the waterline that is unplugged constantly is accurate. You dont need a cehck valve for a DIY CO2 system or for an airpump that is above the water line because in a DIY CO2 system there are no electrics and the system is usually sealed tight. In a pump that is above the water line the water will not rise up into the pump. Gravity and equilibruim is at work here.

I dont see why you wouldnt use a check valve in any case though for a pump either below or above the water line. Its safe, it cost 2 maybe 3 dollars and what happens if someone/something knocks the pump onto the floor when its not plugged in? A simple 2 maybe 3 dollar tool can save you hundereds of dollars. Its safety verses possibilities.
a check valve does nothing but impede the ever so slight pressure of a diy co2 system thus making it even that much more un effective but this is a topic saved for discussion in the corresponding threads not here.
 

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a check valve does nothing but impede the ever so slight pressure of a diy co2 system thus making it even that much more un effective but this is a topic saved for discussion in the corresponding threads not here.

Moneymitch, that's why I said you don't need a check valve for a DIY CO2 system. I was referring to an air pump.
 

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It is acting like a barometer./
 

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They're just too inexpensive not to have. It's a case of preventing something that "shouldn't" happen but could. Besides, I don't believe in "always" and "never".
 
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