This thread is not only serious, but dead serious.
Decades ago when most of us were kids, and drank hose water, like most kids, spray attachments were not put on hoses that dispensed chemicals.
A man sprays commercial weed killer with an arsenic compound in it on his lawn. After he finishes, he disconnects the applicator. It's a hot day, so he takes a refreshing drink of water from the hose. A short time later, he ends up in the hospital, or worse, with arsenic poisoning.
At some time while he was spraying the weed-killer, the water pressure dropped, which resulted in the poison being sucked back (backsiphonage) into the hose. Later, when he drank from the hose, the poison inside was released with the water. Result; he unknowingly poisoned himself.
Many spray attachments do have a backflow prevention device and still, those that do, they sometimes fail.
Besides weed-killer, fertilizers and bug-killers are also dispensed through spray attachments connected to hoses. I know what I've put through my own hoses, you know what you've put through your own hoses, D-Mac knows what he has put through his hoses. But none of us REALLY know what others put through their hoses.
D-Mac is wise to sanitize his tank!