Garden Hose Labeled Safe for Drinking Water
For gravity-fed water systems I recommend 3/4-inch interior diameter hoses over smaller diameter hoses so there will be less surface friction and you’ll get much better water flow. Though note that the couplings at either end of the hose will always have an interior diameter smaller than the hose. For example, a 3/4-inch interior diameter hose will have couplings at either end having a 5/8-inch interior diameter; while a 5/8-inch interior diameter hose will have couplings at either end having a 7/16-inch interior diameter.
You’ll find the 3/4-inch diameter hose has a much better flow rate than the 5/8-inch diameter hose, and far better than a 1/2-diameter hose. Avoid “expandable” hoses as their interior diameter shrinks, and needs more water pressure to expand.
Flexzilla 3/4-inch interior diameter drinking water safe garden hose
Available in 50-foot, 75-foot, and 100-foot lengths. For 25-foot length hose I buy the 50′ hose then cut it in half and insert either a 3/4-inch metal threaded female clinch hose mender clamp (if connected to a low-pressure gravity-fed water cistern/tank), or a 3/4 inch hose barb x 3/4 inch FHT brass threaded female hose repair (which works for both high- and low-water pressure systems). I then have two 25-foot long hoses.
Gatorhyde Drinking Water Safe Garden Hose
Available in 3/4-inch diameter, but upon inspection I found that it constricts down to 5/8-inch interior diameter. Larger diameter hose is best for gravity-fed water systems, since there will be less surface friction reducing flow velocity and volume.
NOTE: This Gatorhyde hose is far better than most hoses which are far more toxic, but Gatorhyde’s is still not perfect. It contains polyurethane, a banned material in the Living Building Challenge Materials Red List (Prerequisite Five). The Living Building Challenge is an integrated green building guide that goes well beyond LEED.
For more info see my blog on this topic: Garden Hose Dangers and Recommendations.