In my basement I have three 55 gal water barrels "w/check valves" in line with my hot water tank inlet. Water flows through all three barrels before reaching my hot water tank. In the event the water goes out I will have the three barrels plus the 75 gals in the hot water tank. This equals 240 gallons. This project started as one 55 gal barrel filled with water. Call me a lazy prepper, but empting and refilling this barrel every three to six months wasn't something I wanted to do. I have posted a diagram pic. I'm curious as to what everyone else is doing. I'm always open to a better way.