All JoJo water tanks are lined with an FDA approved food grade carbon black liner that prevents algae growth, and ensures your water will stay fresher for longer. A JoJo tank does not cause any damage to the water; the quality of the incoming water however may well be an issue. Please remember that water collected from the roof of a building will not be clean. If in emergencies you need to drink the water from the tank, it must be purified. The best way to purify small amounts of water is to bring it to a rolling boil for a minimum of one minute, thereafter it will be fit for human consumption. For irrigation purposes, however, the water would be perfect.
What tends to happen with long term storage is that water goes “flat”. To prevent that you can aerate your water. You could also draw up a tank roster to rotate/circulate the water a set intervals by using that water for a few days to reduce the water level in your tank. Thereafter, you can refill with fresh municipal water (you could wash your car, fill up the pool, water the garden etc.).
JoJo has a 10 year guarantee on material and workmanship. However properly installed JoJo tanks have been known to exceed a lifespan in excess of 20 years.