One way valve leaking-again!

[laka]

I have a one way valve between my bubble counter and Aquamedic 1000 external reactor. My CO2 only turns on with lights. When CO2 switches off the water then diffuses into the CO2 hose up to the one way valve only. After a few weeks however i notice the bubble counter which is normally half full nearly completely filled with water come mornings.
I can only assume that water is percolating through my valve. This is a Dupla valve as well.
Are one way valves not designed for constant back pressure from water?
I doubt having the bubblecounter higher than the reactor would make that much difference because of the significant water pressure present.
I do not want to run CO2 24/24.
How can i solve this problem?

LAKA

 

[Rex Grigg]

Get a decent check valve. The plastic ones designed for air line use break down quite quickly when used with CO2.

 

[laka]

Any recommendation with brand name Rex. I have used two different check valves , the latter being Dupla which i thought would be a good quality valve.

LAKA

 

[wesknox]

Not sure any anti-siphon valves will work well. In the case of CO2 and water, water has such an affinity for CO2 that the water in the tubing will slowly "eat" the CO2 into solution and advance it's way upward...over the top...and down the other side. I have watched it happen in my tubing. As this occurs relatively slowly, the anti-siphon valve never develops enough pressure differential to actuate (close). Given enough time, the water will reach all the way to the solenoid valve. The only way it might stop prior to that would be if the water in the advancing end saturates with CO2 and cannot diffuse rapidly enough to permit further dissolving.

I guess the good news is that it shouldn't run water out of the tank as long as the solenoid valve is closed. Acidic water in the internals of my solenoid valve makes me grimace, though. Purging the CO2 in the line with room air would solve this. A two way valve and a source of air would work. You could also just switch the reactor feed from the CO2 line to open air. This would break any siphon.

 

[laka]

Wesknox i can't seem to grasp the above concept. Are you saying that when the CO2 switches off there is backpressure (or -ve pressure) that sucks water throught the check valve? If i used a two way valve between solenoid and bubble counter that means extra work every morning and if i forget to swith over the valve CO2 will blow into my room! There goes my automation.

LAKA

 

[wesknox]

When the CO2 switches off, CO2 gas still dissolves into the water at the junction gas/water. As CO2 is absorbed and diffuses into water the water advances further into the tube (it creates its own negative pressure). You can observe the phenomenon by filling a length of tubing w/CO2, capping one end and placing the other in water. Let sit for a couple of hours and see what happens. True, you would need to have another gas solenoid to automate this. I haven't actually experimented with these valves, but most modern cars have electically operated vacuum solenoids that are used in emissions control applications. One of these can be had for <$20 and connected to a 12V adapter (aka "wall wart") supplied from the same switched electrical source as your solenoid...you've got your automated vent. I have one of these valves but have never used it as I inherited a commercial aquarium solenoid valve and never finished trying it out on aquarium. The valve will handle the modest pressure you are using and since it only needs to block CO2 and not pass it for long periods, it should last awhile. Anyway that's my theory.

Wes

 

[wesknox]

Oh...one other thing. A "side effect" of this will be that when CO2 kicks on and vent valve closes, a "bolus" of air will be pushed into your reactor...the amount of this air will be a function of how close your vent solenoid valve is to the reactor. I'm not familiar with reactors and whether this air bubble will cause you difficulty over the long term. Air will eventually dissolve in water, albeit slowly.