Heck you got the deadliest weed killer if you got chlorine tablets Bleach deadliest thing known to man(chlorine). It will evaporate so it won't get into your well. Funny how no one thinks of it. How we kept our sewer plants free from weeds inside the fence drop a chlorine tablet in a sprayer . Let it sit over night. then spray all year. But bleach is instant weed killer. Will kill trees also .

Sorry gcp didn't read yours .

Buy a couple of dogs. Mine seem to have the grass destroyed and holes all over the back yard.

I spray around my well with roundup. Herbicides are great when used and mixed correctly. Don’t over use, it only takes 2 oz glyphosate per gallon water. Won’t hurt a thing. Roundup Powermax.

John