I purchased the Chapin sprayer to test in my indoor setting. While I think it would be useful for outdoor gardening or outdoor greenhouses, I do not think it is a good tool for indoors
1.) Metering of ferts does not happen without significant water flow. If you lightly squeeze the trigger no ferts will mix. When the trigger is fully depressed, and the ferts are mixing, it comes out of the single option nozzle at near power washer speed. Impossible to control splashing and watering in an indoor environment.
2) Fert concentrate leaks through hole on handle. There is some type of hole that allows the ferts to leak if the attachment falls over. Fert concentrate stains.
Just wanted to save my fellow indoor growers a few bucks.
I don't know if it applies to the Chapin, but I use an old Ortho Dial-n-Spray for my plants.
It has a plastic "spray" nozzle that clips over an o-ring on the device. I just remove that and hold a 3' piece of 1/2" CPVC pipe over ot to guide the liquid into individual pots without spraying the plants.