Get a controller and you will love that solenoid. Won't run a system without it now. Set the pH span, the offset and the flow rate and I don't worry anymore due to pressure changes in the bottle etc etc.
Had a single probe controller and liked it so much I made a dual probe one so that I can control a Ca reactor and Kalk all in one. Or monitor Ca and tank in one setup.
Next to the auto-top off it is the best investment I have in my tank.
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Darren
Always strive for the optimum environment, not the minimum environment
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