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Re: CO2 Flow Fine Tuning via IV type roller valve

CO2 Flow Fine Tuning via IV type roller valve

Roller valves are an unreliable way to control flows for
long tyime periods because, in effect,  they rely on the
tubing itself as the valve seal.  For these roller valves 
to work you need a pliable tubing like, say, common vinyl

But vinyl tubing is kinda goofy -- it's sort like middle of
the road voter -- it gives in slowly to pressure, but only

Put some vinyl tubing over a fitting on which it just
barely fits snugly and use a strong rubber band for
clamping.  The connection will have a lot of slip, at
first.  But after a few days, as the rubber band continues
to apply pressure, the vinyl will yield and become
compressed more tightly on the fitting.

This works in reverse, too.  If you can't get your vinyl
tubing to slip onto a fitting; try slipping it onto
something barely smaller but very snug -- leave it and 
come back to it later.  It will probably fit the fitting
fine.  (Yes, there are faster ways to get the tubing on the
fitting; I'm just trying to make a point.)

Up to a point, vinyl has some resilience; past that point,
you stretch the vinyl and it's never the same again.

The colder things are, the slower thise process works.  At
some cool temp it doesn't really work at all, the vinyl
becomes too rigid.  But that temp is well below the ambient
temp where most folks keep their aquaria.

So roller valves and tubing make for a poor valve except in
temporary circumstances.

Scott H.

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