The other day, I was talking to Syd Mitchell, Water Quality Guru Extraordinaire. We were discussing ponds that have the propensity to pH crash, and he said he knew of some folks using an Automatic Dosing system for Baking Soda (if you don't know why stable pH or why adding Baking Soda may be important to your pond, you might want to invest a few bucks, and read "Alkalinity and pH"). Syd was explaining how to make your own dosing system - schematic and more info after the break...
A Koi hobbyist who loves hi-tech gadgets asked Syd Mitchell for suggestions for a sodium bicarbonate system dosing system.
Syd says "I used to dose dry powder calcium hypochlorite, (a dry form of chlorine), in an automatic chlorine dosing system for swimming pools. I sent him the attached diagram to show how I did it and suggested that he might copy the idea using a pH controller to control when the system dosed and, obviously, substitute a 5 kg tub of sodium bicarbonate for the calcium hypochlorite."
Syd claims the system is fairly self explanatory. The pump runs whenever the system calls for chlorine and the venturi action sucks powder from the drum. The mixed powder and water runs into an open tank and then back to the pool. The open tank is necessary because a zero pressure after the venturi ensures that there is no risk that back pressure from other equipment might force water back through the pipe and into the powder.
Turns out that the hobbyist didn't use the system as designed but chose instead to substitute the dry powder and venturi for a concentrated sodium bicarbonate solution with a peristaltic pump in the flexible connecting pipe to inject the solution into his filter system.
Karen's Note - there is a pond Dosing Pump on the market, but it runs on proprietary bags of wet chems that K.O.I. would never recommend! However, it might be possible to empty one of the proprietary bags and replace the chems with calcium hypochlorite or some equivalent. If anyone tries that - we'd love to hear about it and post your finding! Contact email@example.com