Uncover the silent culprits behind a spike in your water bill, from hidden leaks to simple billing errors
Opening your water bill to find it significantly higher than last month is always jarring. Before you panic, know that sudden spikes almost always have a cause, and in many cases you can find it yourself in under an hour. A high water bill usually means one of two things: either water is being wasted somewhere in your home, or the bill itself is wrong. This guide covers the seven most common causes of high water bills, how to check each one, and what to do when the problem is out of your hands.
Toilets are the single most common cause of unexpectedly high water bills. A toilet with a worn flapper can waste 30 to 50 gallons per day without making any obvious sound, and a badly running toilet can waste over 200 gallons daily. That is thousands of gallons per month, enough to double a typical household bill.
To check yours, lift the tank lid and listen for a hiss. Drop a few drops of food coloring into the tank and wait fifteen minutes without flushing. If color appears in the bowl, water is leaking past the flapper. Most fixes are simple and inexpensive, as detailed in our guide to fixing a running toilet.
Leaks inside walls, under slabs, or in irrigation lines can dump enormous volumes of water with zero visible signs. A leak the size of a pencil point can waste more than 6,000 gallons per month. The first step is the water meter test: turn off every faucet, toilet, and water-using appliance in the house, then read your water meter. Wait one hour without using any water, then read it again. If the meter moved at all, you have a leak somewhere.
From there, check the obvious suspects first, including appliance connections and outdoor spigots. If the meter moves but you cannot find the leak, it may be in the underground service line or under your foundation, and it is time to bring in a professional who specializes in finding hidden water leaks.
Summer is the season of high water bills for many homeowners. Lawn irrigation can use 1,000 gallons or more per week, and filling pools and running sprinklers for the kids adds up fast. Compare your current bill to the same month last year rather than the previous month, which accounts for the season. If usage matches last year's pattern, you are likely paying for legitimate seasonal use rather than a leak.
Water heaters, dishwashers, and washing machines can all develop slow leaks at their connections that run for weeks before anyone notices. A leaking dishwasher supply line often hides behind the appliance where it is never seen, soaking subflooring and cabinets. Check behind and beneath all water-using appliances for moisture, rust, or warping. A small drip at a supply line that runs continuously can waste hundreds of gallons per month.
Water softeners regenerate on a schedule, and a stuck valve can cause the system to run continuously or waste water in a drain loop. The same applies to reverse osmosis systems, which produce wastewater as a normal part of operation. If you recently installed a treatment system and your bill jumped, ask the installer to verify the settings and check the drain connections.
A leaky hose bib, a broken sprinkler head, or an irrigation line severed by a shovel can soak the ground invisibly while your meter spins. Inspect your yard for wet spots, unusually green patches, or pooling water when nothing has been running. Check every outdoor faucet for drips, and if you have an irrigation system, walk the zones during a cycle to confirm each head operates properly and closes when it should.
Sometimes the problem is not your plumbing at all. Meters can be misread, billing systems can apply the wrong rate, and estimated readings can land far from reality. Compare the meter reading on your bill to the number on your meter. If the utility estimated your usage rather than reading it, the next actual read will correct the discrepancy. If the numbers look wrong or the bill is unusually high with no corresponding usage change, contact your utility company and ask them to verify the reading.
Follow this checklist in order, and you will either find the culprit or confidently rule out most possibilities:
Most hidden leaks are found in steps two through four. If your meter test shows a leak but nothing surfaces in the house, consider that water is leaving through the main line, and call a plumber before the leak worsens and drives the bill even higher.
Letting a leak run is expensive in every direction. Beyond the water bill itself, leaks rot subflooring, damage drywall, and create mold. A toilet that runs for a year can add hundreds of dollars to your bills. An underground leak that saturates your foundation can require thousands in repairs. Finding and fixing leaks quickly is the best financial move available to any homeowner, and the fix often costs less than the leak does in a single month.
If your investigation points to a plumbing problem you cannot locate or repair yourself, do not let it run. A licensed plumber with leak detection equipment can find the source and provide a fix that holds. Professional diagnosis typically pays for itself within one or two billing cycles.
High water bills are rarely a mystery once you start checking. Most causes are quick to rule out, and the two biggest culprits, running toilets and hidden leaks, are both fixable. When you need help finding a leak or repairing the cause, First Plumbing Pro connects you with licensed plumbers in your area who can get your bill back to normal. Call us and find out what your plumbing needs are worth today.