RE: End-of-tank-dump comment -- or - Writing Checks for Check valves

["Kevin Buckley" <kevin at buckley70_freeserve.co.uk>]

The setup is - CO2 tank, tank shutoff valve, regulator + gauges + needle
valve (it's a combined assembly), solenoid, check valve#1, bubble-counter,
check valve#2, reactor.

The bubble counter is a normal, external type: small clear container with 2
airline connectors on the top & 1/2 full of water.  One of the airline
connectors (CO2 inlet) goes to a tube which extends below the water level -
so you can count the bubbles!  The other one (outlet) is just part of the
top of the counter.

When CO2 is flowing it bubbles through the water & out of the outlet.
However, when the CO2 is shut off, the bubble counter water flow back up the
"inlet" (which as stated above is below the water level).

This is really hard to describe in words!!  Take a look at:
http://www.thekrib.com/Plants/CO2/bubble-counter.html.

The first item shows it pretty well.

I agree - the whole thing sounds bizarre but I assure you, the behaviour I
described is what it does & it's pretty obvious when you actually see it
that, if I didn't have check valve#1, the water would go back through the
solenoid & into the regulator!

By the way - I added check valve #2 because without it the water being
"sucked" back down towards the cylinder also sucks water back from the
reactor into the bubble counter which eventually results in the bubble
counter becoming full with water (the water enters through the "outlet" &,
of course, when the CO2 flow reverses it can't get back out again).

Does anyone else on the list know whether CO2 being absorbed into water
would provide enough vacuum to compress a silicone airline flat?

Kevin

======================================
Kevin said, in part:

> My assumption is that the CO2 is continuously absorbed
> into the advancing
> water column as it creeps down the airline (I assume
> also that it diffuses
> out again at the ultimate other end of the water column
> where it meets the
> aquarium water - otherwise I guess the water would
> become saturated with
> CO2 & this process would stop?  Presumably the water in >
the bubble counter
> is always saturated with CO2 whilst the CO2 is flowing?).


Well, anything is possible.  But I always thought it was
hard to get CO2 into water if a vacuum was present, which I
assume is the case if some of the tubing is flattening.
But I surely must not understand your set up.  Pardon my
denseness but you have water on top of the bubble counter?
The water exits the bubble counter and travels downline
towards the CO2 tank or toward the reactor?  Is the bubble
counter an internal device?

I'd expect the setup to be CO2 tank, tank valve, regulator,
solenoid, metering valve, bubble counter (if any), reactor
(or end of CO2 tubing going into a canister intake) -- with
a check valve just before the reactor or just before the
tubing enters the aquarium.  Is your setup different than
this?

Scott H.