unless you know the ph of the water you are starting with there is no way to tell but with distilled water 1 drop would probably be too much for a gal as it probably has very low alkalinity which is the buffering capacity against ph changes. you can get a chemical ph tester at any pet store or even at some walmarts and it's only 5 bucks!
justaseed Reviewed by justaseed on . Anybody with pH utensils do me a solid! Hey my pH meter's in the mail on the mail but I wanna get started on my new grow (see grow log), but I do have a gallon of distilled water (which I'm going to put into a sprayer/mister) and some pH down. How many drops/mL of General Hydroponics pH down do I need to put in a half gallon of distilled water to get to 5.5 (around what you should be doing for propagation correct?) Thank you! Rating: 5