Update... Two things actually. First, I am having a little trouble getting this to work correctly. I have tried both the tube coil and the PVC volume regulator method I mentioned above. Both setups give me a good initial first dose but then I get an intermittent spray or a drop or two every 5-10 seconds. This adds about 5ml or so extra per minute that the pump runs. I have tried several things but none seem to fix, or even change, the problem. I started with a sewing needle hole in the lid and in a 90degree tubing elbow. I slowly expanded the hole in the lid to the size of a paperclip (heated). The bottle I am using is a very thick, 2000ml lab-type Nalgene bottle and the pump is an old, el cheapo "Profile" that was part of a 10 gallon set I pick up long ago.
Also, this happens with the lid on or off and regardless of breather hole size. Both the tubing coil and the PVC chamber do exactly the same thing. It would seem that a venturi forms and a little fluid is continually sucked in to the dosing tube or chamber.
I suppose it would be fine to simple measure the amount dosed for the entire period that the pump runs or get a time that works in minutes. Having one that works in minutes though is a bit counter productive to a cheap setup since a timer is about $30, half the price of an APT peristaltic pump.
Any thoughts on how I can fix this issue?
__________________
Dennis Dietz
|