Pitcher filters look like the easiest way to improve tap water. The sticker price is low, the jug fits in the fridge door, and you do not need a plumber. The real cost, though, sits in the replacement cartridge, and it arrives on a schedule most buyers never write down. Before you add a pitcher to your cart, do the one piece of arithmetic the front of the box leaves out.
Start with the rated gallons
Every pitcher cartridge carries a rated life, usually stated in gallons. Some makers print a number of months instead, which assumes a particular household size. Turn the box over and read the back panel rather than relying on the bold claims on the front. A cartridge rated for 40 gallons will run out quickly if your household draws several gallons a day for drinking and cooking. A cartridge rated for 100 gallons in the same kitchen will last much longer. Two packs can cost about the same and still carry very different true prices.
Do the cost per gallon
Divide the price of the pack by the total rated gallons in that pack. Suppose a two-pack costs $30 and each cartridge is rated for 80 gallons. That gives you 160 gallons for $30, or about 19 cents per gallon. Run the same math on the next box you are considering. Then compare the result with what you already spend on bottled water, using your own receipts rather than a guess. You may find the pitcher is a bargain, or you may find it costs more than the delivery service you thought you were replacing.
Keep one caution in mind. A low cost per gallon tells you nothing about what the cartridge removes. Before you buy, check your own water results and read the certification line for the contaminants you care about. A cheap cartridge that does not address your concern is not a deal.
Count the refills you did not plan for
Rated life assumes ordinary water. Homes with heavy sediment, high chlorine, or a water source that changes with the season may use up a cartridge faster than the label suggests. Watch the filter indicator if the pitcher has one, and note the date you installed each cartridge on the lid or in your calendar. If the water starts to taste or look different between changes, replace the cartridge early rather than stretching it to the next pack. Also plan for the reservoir itself. Pitchers need regular washing, and a dirty jug can undo the benefit of a fresh filter.
Where the bigger promise comes in
Water Finance and Management's column on Chester Water Authority, The Fight to Stay Independent, starts from a simple claim: every public water utility rests on an "implicit promise" to serve the people who depend on it. For a homeowner, a claim is only useful if you can check it. Your pitcher works the same way. The box makes a promise about gallons and removal, and your receipts and your test results are how you check it.
A quick buying checklist
Before you buy a pitcher filter, write down four things: the rated gallons per cartridge, the price of the pack, the number of gallons your household uses in a typical week, and the replacement schedule that follows from those numbers. Then calculate the yearly cost. If the total fits your budget and the certification matches your water, you have found a sensible buy. If the numbers do not add up, consider a different format, such as a faucet-mounted unit, before you commit to a jug that will quietly cost more than it appears.