One drawback of sand is that it will freeze in the winter, making it harder to clean up poop. You might consider gravel, which, if deep enough, will drain better and can be bleached. I used to use pea gravel, which is rounded so that it doesn't hurt feet as much, and which was recommended by the dog school I attend. However, some hounds hate walking on it. There is a smaller gravel (don't recall the name) that does not freeze and is not hard on feet. It might be worth checking with a garden supply or aggregate company.