First, shop around. Prices vary wildly, so check Amazon, home improvement stores, and local plumbing suppliers. Second, look for bundles that include the faucet and installation kit—they save you from nickel-and-diming yourself.
Third, time your purchase. Sales happen on holiday weekends, especially Memorial Day and Black Friday. I snagged my system for $100 off last July—just because it was “Independence Day” for my sink. Finally, ask a handyman instead of a plumber. Handymen often charge less for simple installations, but make sure they know R.O. systems. You don’t want a “close enough” job, unless you’re building a boat and calling it a water feature.
