Dogs elimination area

[wayne]

Hi
I have two dogs. Collie 75lbs & a sheltie 22lb. We live in a town home with a small back area. Here I have always left a small grass area for the dogs to eliminate. I would have to change the sod every two weeks to eliminate odor.
Now I plan to cover the entire area with patio stones. My question is.
Do I just use water to wash away the urine or should I add some sort of urine neutralizer to the water to prevent odor or having a contaminated area?
I know some dogs have a particular run built for elimination but am not sure of what material this consist of.
I appreciate any help, I would like a clean yard but not at the risk of having an area that could be infectious to the dogs.
Thanks / Wayne