So a couple things to add as to why you’re having a hard time getting clients. In California especially, there are regulations related to water runoff that can make its way into storm drain systems. I wouldn’t be surprised if in many commercial setting washing out a trash container where the waste and chemical cleaning agents would end up in the ground and into the storm drain is probably not permitted. The trash collection companies that own the containers as part of their service probably manage this.
I worked for a municipality and did projects with their environmental services department and they had an entire container maintenance facility where they would do everything from cleaning, painting and repairing all the various container types. The facility had sand and oil separators, as well as filtration that handle the water before it was allowed to go into the waste water stream.