When I do mine every spring after flushing out the RV anti I take my water hose empty and pure bleach down the hose attached to inlet than turn on water which will flow through filter less filter housing and into fresh water tank.
Will than run pump to all sinks and washer connections, showers and through water heater.
Will let set over night than flush with fresh water and everything smells fresh and clean.
Will than place new water filters whole house and combo for kitchen sink and ice maker.
You can try this also. From Quick Tips.
If you over do it may have bleached tasting for whole camping season.