Quick answer
Turn off every faucet and appliance that uses water, then check your water meter. If the leak indicator moves, or the reading changes after two hours of no water use, water is escaping somewhere. Closing your main shutoff valve and checking again tells you whether the leak is inside the house or between the meter and the house.
Why a small leak matters
The EPA's WaterSense program reports that the average household's leaks can waste more than 9,300 gallons of water per year, and that about 9 percent of homes have leaks that waste 50 gallons or more per day. Even leaks you cannot see add to the bill and can damage framing, drywall, and flooring over time.
Most leaks are not dramatic. A worn toilet flapper, a dripping faucet, or a slow drip at a pipe fitting can go unnoticed. The steps below help you find them in order, starting with the easiest check.
Step 1: Do the water meter test
This test works because your meter measures all water entering the property. If the meter moves while nothing is using water, something is leaking. EPA WaterSense describes the basic version: record the meter reading, avoid using water for two hours, then read it again. If the reading changed at all, you probably have a leak.
- Turn off all water use: faucets, showers, the dishwasher, washing machine, ice maker, and any irrigation or outdoor taps. Ask others in the home not to flush.
- Find your meter and lift the cover if there is one. Meters are often near the street or the property line, in a box with a lid. Lift the lid carefully.
- Look at the leak indicator. Depending on the meter brand, it may be a small triangular dial or a small wheel that spins whenever water flows. Mercer Island's utility notes that if this indicator moves with all water off, you have a leak.
- If your meter has no indicator, write down the full reading, wait two hours without using any water, and read it again. Any change means water is moving through the line.
- Write down what you saw, including the date and time. A utility or plumber will find it useful.
Step 2: Decide whether the leak is inside or outside
Once the meter confirms a leak, a second check narrows down where it is. This follows the process Mercer Island's utility publishes. Your meter and shutoff setup may differ, so confirm the details with your own water provider.
- Turn off the main shutoff valve for the house. It is commonly in a basement or garage, or near where the water line enters the home.
- With the house water off, check the leak indicator or meter reading again.
- If the indicator stops or the reading holds steady, the leak is inside the house, and a toilet is the most likely culprit.
- If the indicator keeps moving or the reading keeps changing, the leak is on the line between the meter and the house. That is a job for a plumber.
Step 3: Run a toilet dye test
Toilets can leak silently into the bowl where you never see it. EPA WaterSense recommends a simple dye test: put a few drops of food coloring in the toilet tank, wait 10 minutes without flushing, and see if any color appears in the bowl. If it does, the toilet is leaking. Flush right away afterward to avoid staining the tank.
EPA also advises checking toilet flappers periodically and replacing them at least every five years. A worn flapper is the usual cause when dye shows up in the bowl.
Common hiding spots for leaks
If the toilets pass and the meter still moves, work through other likely spots. Look for damp, stained, or warped material, and listen for hissing or running water in the walls.
- Faucets, showerheads, and the supply lines under sinks. EPA notes that a faucet dripping once per second can waste more than 3,000 gallons per year.
- Pipe fittings and valves, including the water heater connections and the washing machine hoses.
- Outdoor hose bibs and garden hose connections at the spigot.
- In-ground irrigation systems. EPA suggests checking them each spring, and notes that a leak only 1/32 of an inch wide can waste about 6,300 gallons per month.
- Walls, ceilings, and floors near plumbing. Stains, bubbling paint, soft flooring, or a musty smell can point to a leak inside the structure.
What a high water bill can mean
A sudden jump in usage is often the first sign of a leak. EPA WaterSense suggests comparing a cold-weather month, such as January or February, when outdoor watering is not a factor. A family of four using more than 12,000 gallons in a month may have a serious leak.
Not every high bill means a leak. Guests, new appliances, and seasonal watering all change usage. The meter test separates a real leak from higher use, because it shows flow when nobody is using water.
If you are a utility customer, ask your provider whether it offers any leak adjustment or repair deadlines. Seattle Public Utilities, for example, asks customers to start locating a customer-side leak within 30 days of the first notice of increased usage and finish repairs within 60 days. Policies differ by utility, so check yours.
A note on slab leaks and buried lines
Some pipes run under or inside a concrete slab, or underground between the meter and the house. You cannot see or reach them, so the meter test is often the first sign something is wrong. If the test shows a leak, the toilets are clear, and nothing is visibly wet, the leak may be in one of these hidden lines.
Pinpointing it usually takes specialized detection equipment and a plumber, not guesswork. Cutting into floors or digging up a yard without knowing the location can cost time and cause extra damage.
What to do next
Shut off the water at the main valve if you see active flooding, hear water running behind a wall, or cannot find the source. Turn off nearby electrical power only if you can do so safely and without standing in water. If water is near outlets, panels, or appliances, stay out and call an electrician or your electric utility. Pyper does not do electrical work.
If you smell natural gas at any time, leave the building right away and call 911 or your gas utility from outside. Do not use switches or phones near the smell. Pyper does not do gas line work.
When to call Pyper Plumbing
You can call us when the meter test shows a leak you cannot trace, when a toilet or faucet keeps leaking after a simple fix, or when water is showing up in a wall, ceiling, or floor. We handle leak detection and repair, as well as emergency repair when a pipe is actively leaking.
If you are not sure whether what you found is serious, tell us what the meter did and where you looked. That information helps us decide how to approach the problem.
Common questions
How long does the water meter leak test take?
About two hours. Record the reading with all water off, wait two hours without using any water, and read it again. Any change suggests a leak. If your meter has a leak indicator, it can show flow immediately.
How do I check a toilet for a leak?
Put a few drops of food coloring in the tank, do not flush for 10 minutes, and check the bowl. Color in the bowl means the toilet is leaking, usually from a worn flapper. Flush afterward to avoid staining.
Can a hidden leak raise my water bill?
Yes. Even small leaks add up. EPA WaterSense says the average household's leaks waste over 9,300 gallons a year. A family of four using over 12,000 gallons in a winter month may have a significant leak.
What if the meter shows a leak but I can't find it?
Close the main shutoff and check the meter again. If it still moves, the leak is between the meter and the house. If it stops, the leak is inside, so check toilets, fixtures, and fittings, then call a plumber.
Sources
Facts in this guide come from the following references. Local rules and manufacturer instructions can differ, so follow your utility and your equipment manual.
- EPA WaterSense: Fix a Leak Week
- City of Mercer Island: How to Understand Your Water Meter
- Seattle Public Utilities: Leak Adjustments (customer service document)
This guide is general information, not a substitute for an on-site inspection. If you smell natural gas, leave the building and call 911 or your gas utility. Pyper does not perform gas line work.
