water pipe thickness

Are you asking what the standard sizes of pipes are? If so, there are a lot of websites with charts - just Google "Pipe dimensions"

Or are you asking what a required thickness is for a certain condition? If so you need to provide a fluid pressure and applicable code. Even then it will be a little tricky to give you an answer because depending on the code, there are other considerations including pipe layout (dimensions), support distances, thermal expansion, seismic, weight of insulation, etc ...................

???? What water pipes? Galvanized/PVC/Stainless Steel?

They are in gauge/schedule 20/30/40/ etc.

Ask your Pipe Supplier to give you the Chart or look up the internet.

[e.g. http://www.acipco.com/adip/pipe/pressures-weights/pandw.cfm]