This is an explanation of HOW TO set up a gravity style water system.
First, if you live in a city you may as well stop reading right now, because this information is not pertinant to your geographical location or lifestyle. There is a lot of physical work involving quite a bit of digging as well as staging the components of this system up on the side of a mountain or hill.
I bought my parcel of land in 1978 after searching for over a year. My first priority was a good supply of clean, potable water. I chose this area of the country for its mild wet winters and this particular parcel because it has a creek running through it that flows year round, as well as a 2 springs that are located up on the side of a mountain. These springs are ringed by a perimeter of LaGuardia ferns, which the pioneers always looked for because these ferns are an indicater of good drinking water. The upper spring is about 40 feet in elevation above my housesite and 60 feet above the flat spot where I have a barn, vegi garden / fruit trees etc. This is not a great distance in elevation, but enough to give me enough water pressure to run the shower and fight fire if needed. ( A drop in elevation of 27&3/4 inches produces one pound of water pressure. This is known as a water column. The plumbing fixtures in your house work on about 40 pounds per square inch. Too much drop in elevation will give too much water pressure and will blow the washers out of your kitchen sink etc.) My spring sits on a shelf of blue clay, which traps the water and prevents it from perking into the ground. The first step is to dig out the spring site so that you can build a spring box to define the spring, and keep unwanted debris from entering the water. Some people use redwood for a springbox but I used a 55 gallon foodgrade plastic pepper barrel with a large screw on top. I drilled 1/8 inch holes over the entire surface of this barrel, approx 2" apart, and installed a threaded 3/4" polly hose connector in the side of the barrel about 6" from the bottom. Digging this hole was the hardest part of this operation, as well as digging a trench for the waterline from the springbox to the water storage tank. I backfilled the outside of the springbox with drainrock which acts as a filter, and allows the rainwater to perk into the springbox. This rock was packed up the side of the mountain in 5 gallon buckets, another real backbreaker! So, it rains, water runs through the holes and is collected in the springbox, then travels through the 3/4" hose about 60 feet downhill to my water storage tank. From the tank runs a 1" dia. NSF type poly hose, 900 feet down the side of the mountain to a water filter and the house. This entire operation took about 3 months to install in my sparetime. The water is FREE, pure and we have never gotten sick from it. Of course this system will freeze solid in colder climates unless its buried at least 5 feet deep and you must winterize the springbox and holding tank. My system has been in use for 29 years now. It requires a cleaning every other year and I flush it out with bleach at these cleanings. No other maintenance has been required.
Toepopper