Those 1 gallon hand pump sprayers are usually less than $10 bucks at my local walmart. You can buy one for each product you use they are so cheap. I like the back pack sprayers just because I get tired of pumping. I recently saw Ryobi now makes some rechargable battery powered sprayers, one little one thats used to spray disinfectants and such, looks like it would be perfect for spraying down plants in room sized grows. I might pick one up to mess with, I was thinking the small sized one below because it supposedly atomizes it into a penetrating fog.
Small
Medium
The RYOBI 18V ONE+ Battery Chemical Sprayer is the perfect union of portability and versatility. With its pump optimized for cordless efficiency, it sprays 20 tanks per charge with no pumping required.
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Large
The RYOBI 18V ONE+ 4 Gal. Backpack Chemical Sprayer combines the convenience of a cordless sprayer with a backpack design to allow you to work quickly and comfortably. This sprayer is powered by a 18V
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