Why Your Water Bill Jumped, and How to Find the Leak

Why did my water bill jump when nothing changed at home?

Because something did change, you just cannot hear it. Water leaves through the same meter whether it goes down a drain on purpose or into the dirt by accident. For most houses the bill is the only leak alarm there is, and it shows up two months late.

The federal WaterSense program puts the average household's leaks at more than 10,000 gallons a year, and says 10 percent of homes waste 90 gallons a day or more. A faucet dripping once a second throws away over 3,000 gallons a year. A toilet that runs constantly can waste 200 gallons a day on its own. Those figures come straight from the EPA WaterSense statistics page, and they match what we dig up in Sonoma and Marin yards.

The good news is that the same program says fixing the easy leaks cuts a typical water bill by about 10 percent. Most of what follows you can do yourself in half an hour with no tools.

How do I use my water meter to find a leak?

This is the test that answers the question. Your meter sits in a concrete or plastic box near the street, usually under a metal lid you can lift with a screwdriver.

1. Turn off every fixture in the house. No dishwasher, no washing machine, no ice maker cycling, no drip irrigation running.
2. Pop the meter lid and find the leak indicator. On an older dial meter it is a small red or blue triangle, star, or spinning disc. North Marin Water District tells customers plainly that a circular motion by that indicator means water is moving.
3. Watch it for two minutes. If it turns at all, water is going somewhere.
4. If your meter is digital, write down the reading, then take another reading two hours later with the house still shut down. Any change is flow.

Marin Water and North Marin Water District customers with newer AMI meters get a shortcut. Log in to the district portal and look at your hourly use overnight. A house with no leak drops to a flat zero between 1am and 4am. A house with a leak shows a low, steady line that never touches bottom.

How do I know if it is the toilet?

Toilets are the number one hidden leak in Sonoma and Marin homes, and a bad flapper is silent once the water level settles below the overflow tube. Take the tank lid off, drop in a dye tablet or ten drops of food coloring, and do not flush for 20 minutes. Color in the bowl means the flapper is passing water. Santa Rosa Water hands out free dye tabs to customers who ask, and North Marin Water District gives the same test in its FAQ.

A flapper is a $12 part. If the tank still runs after you swap it, the fill valve or the flush valve seat is the problem, and that is a short visit rather than a new toilet.

What if the meter still moves with everything off?

Then walk it outward, one shutoff at a time.

• Irrigation first. August is peak landscape season here, and a cracked lateral or a stuck valve under a lawn shows up as a green patch and a huge bill. Close the irrigation shutoff and recheck the meter. If it stops, the leak is in the yard piping, not the house.
• Then the house valve. Close the main shutoff at the house and watch the meter again. Still turning? The leak is in the buried service line between the meter and the building, and that is a dig.
• Hose bibs and the pressure regulator. A weeping hose bib or a failed regulator behind the front hose spigot runs constantly and drains into gravel where nobody sees it.
• The water heater. A dripping temperature and pressure relief valve usually means thermal expansion has nowhere to go. On a closed system with a regulator or a backflow device, code wants an expansion tank, and our cost guide puts that part at $150 to $450 installed. A T and P line running into a floor drain can waste water for months without a stain.
• Water softeners and filters. A softener stuck in regeneration will cycle to drain all night long.

If you are not sure where your main shutoff is, find it before you need it. We wrote a walkthrough for exactly that, and it takes five minutes on a dry day instead of five panicked minutes in an inch of water.

Will my water district give me credit for the leak?

Sometimes, and the rules are strict, so read them before you call. Marin Water runs a loss of water adjustment for customers who have fully repaired the leak, and it is limited to two billing periods and one adjustment every 36 months. Marin Water does not adjust for faucet leaks, and the customer still pays part of the calculated loss. The City of Santa Rosa also caps its leak adjustment at two billing periods and one adjustment.

Two things follow from that. Fix it fast, because the clock is on the repair date, not the discovery date. And keep the invoice, because every district wants written proof of repair.

When is it time to stop testing and call somebody?

Call when the meter keeps turning after the house valve is closed, when you hear running water inside a wall, when a slab floor has a warm spot, or when the bill doubled and none of the tests above found anything. Those are pressurized supply leaks, and they get more expensive every week they run.

CNTRline has worked Sonoma and Marin since 2017, we answer 7 days a week, and quotes on most jobs are free. Call (707) 308-5599 and we will help you narrow it down before anybody starts digging.

Related repairs: faucet and fixture repair for the drips you can see, water heater repair for a relief valve that will not stop dripping, and emergency plumbing when the leak is already running across a floor.