With a rainwater harvesting system, once you have filtered water in the storage tank, there are three ways to get it out: with a hand pump, electric pump, or gravity.

Most of the rainwater storage tanks available to homeowners come equipped with a standard garden spigot near the bottom of the tank where you can quickly hook up a garden hose (this is the option that takes advantage of gravity to provide the necessary pressure for watering).

But for larger irrigation systems or systems where most water is stored below grade, a pump is generally required to get the water out of the storage tank. There are two types: hand pumps and electical pumps.

Hand pumps don't require electric energy but they can require energy of the human kind.

An electric pump will cost more, for material, installation, and operation, but will enable you to water plants in a raised or hanging location without a struggle. Then again, you might save money by eliminating your gym membership.