sanitize fresh water tank
When I sanitized my fresh water tank and all plumbing in the system from the day I brought home and once after no use for six weeks I used bleach clorox. First I empty my water hold tank , added 6 Oz bleach refilled fully over 100 plus gallons. Ran all faucets , hoses, toilets and shower hot and cold individual till I could smell the bleach. Let sit for 24 hrs and dumped my water hold tank.refilled not fully with fresh water and ran all water outlets till no smell of bleach and I was satisfied of cleansing .
Not telling anyone this is safe or perfect only sharing what I have done in the past. I had an pneumonia from a disease in water from a cabin that we rented that sat unused for a year.I don't take chances with new construction and old sitting water after that stay in hospital. When u shower water goes in your body , same with brushing teeth , washing your face , cooking etc. I used bleach on other boats , new plumping projects and last camper with good luck.Always looking for better fixes etc.be safe