There are a couple ways to approach your pool – one is to clean the stones with a solution of muriatic acid and water (carefully though – if anything has artificial color it will take it away.) It will clean up salt residue, etc. Just test first to make sure the stones won’t be damaged in the process.

Another method is power washing – gently – and test on the stones to make sure they can handle it. Over time some stones become too fragile to do this with, but in other cases, like with our bluestone, it holds up very well under power washing.

Some commercial cleaning companies have become well versed at cleaning outdoor areas – and sealing. If one is available in your area, you could try that.

Then I would head to the local supplier where pool guys would purchase their products – specialty stone or tile shops and get the right seal for the type of stone you have – there may be a little different recommendation for each flagstone and sandstone because of the differences in the stone hardness/porousness etc. A company we use that sells to the public- and landscape supply yards should have a recommendation.

When we use natural stone on our projects we often leave it to weather and perform maintenance as needed – though in some cases we do seal – so that being said if you clean it up and it looks nice you can just leave it and plan another clean up after a number of years.