Cleaning a spray tank

[BR Green]

We have an old tank in storage that was previously used to spray chemical fertilizers. All of our customers are on organic now and I'm wondering if it's possible to clean it out for compost tea usage. Does anyone have any suggestions about cleaning it out properly?

[lawncuttinfoo]

Why cut corners, buy a new tank, they are cheap.

There is no way to know how much chemical has seeped into the plastic. You will have to do continuous testing to confirm is not killing the microbes at any stage.