DE only afects things with exoskeletins. it pokes them full of holes. think a bollon on broken glass. google DE then select pics they are very pretty to look at, but kave very sharp edges
i use a product called (snake a way) works with rattle snakes tj
im guessing that buying a mongoose is not an option?
DE is a must have if one has pets of any sort. Unfortunately, DE has no effect on larger animals. Snakes have thick tough skin as well as scales. I am lucky if I see a garden snake here. In fact other than small moles, I have almost no vermin to attract snakes. When I lived in California so many years ago, we used to carry a mixture of fresh crushed garlic cloves and rock-salt to throw at them when hiking, however, I don't think it applicable in your situation. Another rumored method that I use but cannot confirm is the use of marigold plants. About four years ago, I designed an IPM (integrated pest management) theme landscape for a dairy processor to discourage rodents.
I know the frogs ang the water and frogs will attract snakes come summertime. My outside lab used to howl every. ight as the copperhewds owuld slither throuegh his dog house on the way to the water souce. They never bit himbut he didn't like yhe company. When we had an above ground pool, it quickly turned into a breeding pond for frogs. I kind of hope tht will hppen again so the polywogs help feed the blugills. athanks to evryone. I'd consider the mongoose if I could eat it afterwards.
I once lived in a city near you in an area called the "golden triangle". The copperheads liked the wild dewberries and blackberries that grew alongside the railroad tracks and the cottonmouths lived all along all the waterways. A friend of mine's son got bit on the finger playing with one two summers ago. He was embarrased and tried to hide it until his hand almost popped from the swelling. I think he is still grounded.
I realize that this thread is about DE ...Not knowing your situation as far as neighborhoods, etc.. I do have one solution for you. Peacocks will successfully kill venomous snakes. Out here a few miles east (the dry side of the Cascade Mtns.) a few farms keep peacocks to control the wasp/hornet and venomous snake population. Peafowl do this superbly! We do not have copperheads in our "neck of the woods", so I checked online to see if this held true for copperheads and peafowl, and it is! So if you are in a situation for be able to have peafowl, this would be a natural way to keep your area safe. I do know a bit about peafowl, though not an expert, as we have been raising them on our farm for a while.
I am not trying to start a debate about those who like or do not like peafowl. I just wanted to offer another solution to your problem. Hopefully if the DE won't work, you can find another solution that will work. My best to you in this!