We bought a used sprayer last year, 1200gal, pull type. We are certified organic so I had no prior experience with chemicals or sprayers.

I was told it had been used for both liquid N fertilizer and Dicamba most recently.

I first got all new mesh screens and nozzles . Then I used different cleaning agents.

(For each step I filled the sprayer at least 2/3 and agitated it for 5-10 min before running it out through the boom for about 5 min, then just draining the rest.)

I did one wash with some Dawn dish soap. Another with a “sprayer cleaner” powder I found at a local farm supply store. I also did one with a bit of bleach. Ideally I would have done one with an ammonia cleaner, but didn’t feel like making another trip to town to find some.

Then I did a couple good rinse flushes.

I looked around to see what other farmers were using. It’s common for farmers to switch between multiple herbicides that each have different modes of action and take different chemicals to neutralize them. (I read of some “horror stories” of farmers killing off a few hundred feet of crop because things weren’t cleaned out well enough between types of chemicals. So they are well versed in how to get things clean.) After looking up what the most common cleaning methods for a few major chemicals were (Round Up, Dicamba, Atrazine, 2-4D etc.) I went with my above approach.

I didn’t do a microscope test to check on biologicals, but my first treatment was a fertility foliar with minimal biology, so I wasn’t too concerned with my first load.

Hope that helps, or at least gives you another resource to search with!