Cleaning Flagstone

I have a patio where his FLAGSTONE get dirty, I have often washed with soap and water and a broom but thats a tough job. Beter Is it possible to do so, perhaps some special chemicals.

Mauriac acid, this was my dads house on the porch ... I can remind him to use it and taught me how to use commands! Wear gloves and read instrution .........

Try a pressure washer as it will not damage the patio. It depends on how it is constructed. If you can use it they work hard and are fairly easy to use.