Is this when heating the water?.......if so build up on electric element. Drain and power flush WH tank using a WH cleaning wand OR by turning on water supply with drain plug out. Depending on amount of build up you may have to remove element to clean (or replace).
If this is occurring when you are using hot water then the check valve in WH hot outlet is chattering......due to scale build up or because it is coming apart.
Check valve is internal of outlet nipple on WH tank. Replace it OR tear the internals out and install a valve on hot outlet line. Check valve is only needed when bypassing WH when winterizing.
You are in a very hard water part of the country.......so probably have both problems
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