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High water bill in Cambridge? How to find the leak and apply for the City's leak adjustment
A Cambridge water bill that suddenly doubles almost always means water is running somewhere it should not be. The City has a limited relief program for high bills, but only after the leak is found and fixed, so the order you do things in matters.
Last updated September 25, 2026 · Reviewed by the Cambridge Plumbers team
Step one: prove there is a leak with the meter
The City of Cambridge owns the water meter, which is normally in the basement where the water service comes through the foundation wall. The piping from the property line into the house, including the valves on either side of the meter, is the owner's to maintain. You can run your own leak test in fifteen minutes:
- Make sure nothing is using water: no dishwasher, laundry, softener regeneration, humidifier or irrigation. Ask everyone in the house not to flush.
- Look at the meter face. Most meters have a small low-flow indicator (a small red triangle, a spinning wheel or a fast-moving last digit) that moves with even a trickle.
- Write down the full reading, wait 15 to 30 minutes without using water, and read it again.
If the indicator moves or the reading changes, water is leaving the pipes somewhere downstream of the meter. If nothing moves, the high bill may be a usage change (a new tenant, a pool fill, a lawn sprinkler) or a billing question for the City.
Step two: check the usual suspects in Cambridge homes
Most high bills come from a short list, and Cambridge's hard water makes several of them more likely.
- Toilets. A worn flapper or a fill valve that never shuts off can run continuously and silently. Put a few drops of food colouring in the tank, wait 15 minutes without flushing, and look in the bowl. Colour in the bowl means the flapper is leaking. Water running into the overflow tube means the fill valve is set too high or failing. Scale from hard water is a common reason both parts stop sealing.
- Water softeners. A softener stuck in regeneration, or one set to regenerate far too often, can send large volumes to the drain. Listen at the softener drain line and check its settings.
- Water heater relief valve. A temperature and pressure relief valve that drips or trickles into a floor drain is easy to miss. The discharge pipe should be dry.
- Outdoor taps. A frost-free hose bib that split over winter can leak inside the wall only when the tap is opened, or leak constantly if the valve seat is damaged.
- Humidifiers and reverse osmosis units that drain continuously.
- Hidden pipe leaks. In Galt and Hespeler century homes, pinhole leaks in old copper, weeping joints on galvanized steel and slab or wall leaks do happen. Look for damp drywall, stains on ceilings under bathrooms, or a warm spot on a basement floor.
Step three: isolate it
If the meter still moves and you cannot see a leak, shut off the fixture stops one at a time (toilets, then sinks, then the softener bypass) and recheck the meter after each. When the indicator stops, you have found the branch. If it keeps moving with every fixture isolated, the leak may be in the supply piping itself, or between the meter and the main shut-off. That is a job for leak repair and pipe replacement, not guesswork.
Old main shut-off valves in Cambridge's older houses often do not close fully. If yours will not stop the water, do not force it; a seized gate valve can break off in the pipe. The plumber can replace it with a ball valve, which may require the City to close the curb stop first.
The City's high water bill adjustment
Cambridge offers limited financial relief to residential and not-for-profit water customers whose bill spikes because of a leak. According to the City, you must meet all of these conditions:
- The bill was issued within the last 90 days.
- The extra water is at least twice your average consumption.
- You have not received an adjustment in the past 12 months, and you have had no more than two in 10 years.
- The problem has been identified and repaired, and you can prove it.
The proof requirement is where most people get stuck. Keep the plumber's invoice showing what was repaired and where, photos of the failed part, and your before-and-after meter readings. Applications are made online through the City. The relief is partial, so the faster the leak is found, the smaller the bill you are asking about.
Free help from the Region
The Region of Waterloo runs a free Home Water Review for households using well above normal amounts of water. A Region representative looks at your meter readings, checks fixtures and appliances for leaks and, for homes with softeners, tests your water hardness. It is worth booking if the bill is high but you cannot find an obvious cause.
When to bring in the plumber
Call if the meter shows a leak you cannot isolate, if you find water in a wall or ceiling, or if the fix involves the main valve, a softener or a relief valve. The plumber covers Galt, Preston, Hespeler and Ayr, and the written invoice they leave is the proof of repair the City asks for. For typical repair ranges, see the Cambridge plumbing cost guide, or send a description of the problem.