The use of graywater is a gray subject.
Graywater is water from your bathtub, laundry or bathroom sink.
Plants are not harmed by normal amounts of detergent in graywater if you apply it immediately.
Storing graywater, though, is not a good idea. You’ll quickly encounter the stink of anaerobic decay if you keep a barrel of the stuff for more than twenty four hours.
The use of graywater comes under the jurisdiction of several governmental entities, depending on where it is applied.
Near a stream, the Georgia Department of Natural Resources might have an interest. In your own backyard, your local health department or plumbing code enforcement folks have jurisdiction.
Before you approach anyone for a permit, visit Graywater Central and bone up on the basics.
Applying graywater in a landscape is also regulated by the Georgia EPD rules. They say:
(1) This rule shall not apply to the following outdoor water uses:
(b) Re-use of gray water in compliance with applicable local ordinances.
Bottom line: you can use water from your bathtub, laundry or bath sink without harming plants….but, strictly speaking, you can’t apply it without a permit.
I’ll let you make your own decisions.