A water meter can answer a question that is hard to answer by looking at a faucet: is water moving through the house when nothing should be running? For St. Louis homeowners with a reverse osmosis unit or other under-sink treatment, this check helps separate a problem with the filter setup from a leak somewhere else in the plumbing. It takes a short time and needs no special tools.
What the Meter Tells You
Most residential water meters have a register with a numbered dial or digital readout. Many also have a small leak indicator, often a triangle, star, or spinning dial, that moves whenever any water passes through. Your meter may sit in a basement near where the main water line enters, in a utility closet, or in a box near the front property edge. If you are unsure where yours is, start at the point where the water line comes into the home, then check outside for a lid or box near the street.
Before You Start
Pick a time when nobody will use water for a while, such as overnight or when everyone is out.
- Turn off all faucets, including outdoor hose connections and any sink sprayers.
- Shut off the dishwasher and washing machine, and confirm the ice maker is not filling.
- Note whether your reverse osmosis storage tank is refilling, since a tank refill looks like a leak.
- Make sure the water heater is not refilling after a recent hot water draw.
Running the Check
- Find the meter and write down the reading exactly as shown, including any leading digits.
- Look at the leak indicator. If it is moving, water is passing through the meter even though you think nothing is running.
- Wait until the house has been quiet for a good stretch, long enough that no fixture would still be filling, then read the meter again and compare.
- If the number changed or the indicator kept moving, something is drawing water.
- If your setup has a shutoff for the filter feed line, close it and repeat the check, then compare the two results.
Reading the Results
The meter moves with everything off
This points to a leak in the house supply or in a fixture. Common places include toilet flappers and fill valves, an outdoor hose connection, a water heater fitting, and a supply line under a sink. A food coloring test in a toilet tank can show whether the tank is letting water slip into the bowl. Keep notes on each check you do so you can narrow down the source.
The meter stops when the filter feed is closed
If the reading holds still with the filter feed closed but moves with it open, the leak is likely in the filter line, a fitting, or the tubing running to the unit. Look under the sink with a dry paper towel wrapped around each connection, then check the nuts, tubing ends, and valve body. Tighten a loose nut only gently, and do not overtighten plastic fittings.
The meter stays still
A steady reading over a quiet period suggests no active leak at the moment. Slow leaks can be intermittent, though, so repeat the check on another day, especially after a cold snap or a long stretch of heavy household use.
Notes for St. Louis Homes
Many older St. Louis homes have meters that sit in basements or crawlspaces, where pipes can be exposed to winter cold. Keep the meter area clear and dry, and avoid working near a meter in a damp or flooded basement. If the meter is in a below-grade box, be careful around the lid and any standing water. Older service lines may also have buried joints that leak without showing much above ground, which is one reason the meter check is worth doing before you open walls or cabinets.
When to Call a Professional
If the meter keeps moving with all fixtures off, and you cannot find a source after checking the toilets and visible connections, a licensed plumber can use specialized tools to locate hidden leaks. If you suspect the leak is on the utility side of the meter, contact your water provider. Do not dig or open the meter box beyond what is needed to read it.