If you are using your coach every weekend no need to drain. The fresh water tank was bleached the begining of season and I will freshen and drain during season, use mostly for toilets, in camp grounds most of the time. Your HW needs to be used also or your will smell rotten egg smell if not used and more quickly in the hot weather. When flushed with bleach in spring did HW heater also. If you continally use coach should not have a problem.
They do have chemicals that are safe for fresh water tank but alot of RVers do not care to use.
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