Do you need to sanitize a water tank that's never been used?

It would be a good idea to sanitize it.

Do you use dishes when you get them home from store, or do you wash them first?
I would sanitize it. OTOH, I don't wash dishes in water I would not drink.

Do you know the history of the tank prior to being put in your RV?
I assume not, In which case making sure it is clean and sanitized is a good idea.

yes do the whole system,you don,t know whats crawled in there.I do mine couple times a year,it don,t get used much.

Even right off the factory line I'd still sanitize it, but sitting since 2018 I'd be even more inclined to do it.

……. We never bothered to sanitize our freshwater tank! Reason is that we DO NOT DRINK from the tank. Rather we bring containers of drinking water with us ( using a 5 gallon blue jug & also we reuse empty juice bottles filled with good local water. )… Has worked well for us for years!…

If it makes you feel better go for it but since you say it's "never been used once", I'm assuming a brand new trailer and it really isn't needed.

I might fill and then pull the drain plug in case any dust go inside but unless you have reason to believe it was contaminated, I really wouldn't worry about it.

We've also never bothered to sanitize our fresh water tank...and WE DO DRINK FROM IT. Been doing it 4-8months of travel per year for the last 12yrs and on vacations for the last 50yrs. Never had any issues.

To sanitize or not to sanitize is totally your call, we sanitized our FW tank initially after purchase but for the most part we use FW tank for dishes, showers, and toilet use. We prefer bottled water for personal consumption and bring a couple of gallons of RO water from home for cooking.

Absolutely! An ounce of prevention is worth a pound of cure. Filling it and dumping will get the dust etc. out. Adding bleach is easy. Run the bleach water through the water lines too.

Sanitize