I think they make a spray tank cleaner. I have used it for three years now. Put the solution in with water, let it sit for 15 minutes then empty. I put some pressure in the tank and spray the solution through the wand and nozzle as well. So far so good.
Only trouble I have noticed using Dawn is that the soap foam takes many, many cycles of rinsing to get it all to run clear. Plus I think they have changed the formula in the last few years. I notice to get the same cleaning done I have to use a lot more of their liquid.
I wonder if the He soaps would work better - they’re made to be low-suds
They have taken the phosphates out of all the soaps so they are a lot less foam than they were before. I just know that even to clean certain things with Dawn I have to use a lot more liquid. Probably X 2. We used it in the fire service to clean a lot of our items and it was great. Just now the amount we use is crazy high.
Monterey Lg1140 Spray Tank Cleaner, 1 Pt is what I use to clean out my spraying tanks. It has been working for me the last few years. I do not use Dawn because I feel if there is residue left over it may effect the chemicals I am putting in the tank to use next. Maybe that is something I should not worry about but in my mind it makes sense.
I use oxyclean to clean basically everything. It completely obliterates any organic matter and grime which makes it perfect for cleaning my brewing equipment before storage. It doesn’t leave any residue that i noticed but if you are worried about it I believe i read it can be neutralized with an acid.