# Fix a Leak Week: A Leak Check for Older San Francisco Pipes

> Fix a Leak Week comes every March. For older San Francisco pipes, check SFPUC hourly meter data, threaded galvanized joints, copper pinholes and leak credits.

URL: https://hilltoprepipesanfrancisco.com/blog/fix-a-leak-week-old-pipes/

Dates and Deadlines

Each March, the EPA's WaterSense program runs Fix a Leak Week. In an older San Francisco building, the useful version of that check goes past the toilet flapper to the pipe itself.

Last Updated: October 30, 2026

Every March, the U.S. Environmental Protection Agency’s WaterSense program runs Fix a Leak Week, a reminder to look for the drips and running toilets that waste water at home. In a newer house, that check mostly means flappers and faucet washers. In an older San Francisco building, where galvanized steel and decades-old copper still carry the water, it is worth going one step further and looking at the pipe. [Hilltop Repipe San Francisco](https://hilltoprepipesanfrancisco.com/) offers and manages [water leak detection](https://hilltoprepipesanfrancisco.com/water-leak-detection/), [pipe repair](https://hilltoprepipesanfrancisco.com/pipe-repair/) and repiping in San Francisco, Daly City and South San Francisco, carried out by licensed and insured contractors, and this is the check worth doing whichever week you do it.

## Start with the meter data, not the meter

San Francisco households don’t need to open the meter box, and SFPUC asks customers not to touch meters at all. Its automated meters record use every hour, and SFPUC’s MyAccount shows that hourly use. The test is simple: look at the small hours of the night, when nobody is running water. If hourly use never reaches zero, something is running, and SFPUC says a leak is then likely still unresolved.

SFPUC also watches for this on its own. For single-family homes and buildings of two to five units, its courtesy Leak Alert Program flags 48 hours of continuous use of at least 1 cubic foot, about 7.5 gallons, per hour. For larger buildings it flags overnight use well above the building’s 90-day average. An alert is a reason to look, not a diagnosis; the [guide to SFPUC leak alerts](https://hilltoprepipesanfrancisco.com/guide/sfpuc-leak-alert/) explains what each one means.

## What a slow leak costs at San Francisco rates

A leak at that 7.5-gallon-per-hour alert threshold, running for a 30-day month, wastes about 5,400 gallons. At SFPUC’s current single-family water and wastewater rates, for a household already past the first tier, that works out to roughly $233 a month on the bill. Rates are set each fiscal year, so the figure moves, but the arithmetic is the point: a leak too small to hear can cost more each month than the repair.

## Where older pipe leaks first

Older supply pipe fails in predictable places, because each material has a weak point.

- **Galvanized threads.** Galvanized steel corrodes from the inside, and the threaded joints, where the wall is thinnest, go first. A damp or rust-stained joint along a garage or basement ceiling is the classic early sign.
- **Copper pinholes and joints.** Copper usually fails at a pinhole in the tube wall or at a soldered joint. Green crust around a joint, or a fine spray from the middle of a pipe, are the signs. No single cause explains every pinhole; the [copper pinhole leaks guide](https://hilltoprepipesanfrancisco.com/guide/copper-pinhole-leaks/) covers the candidates.
- **Where copper meets steel.** Two metals in contact form a galvanic couple, and the steel corrodes faster at the joint. San Francisco’s code requires a dielectric or insulating fitting there; where an older mixed system lacks one, that joint tends to leak first.
- **The water heater connections.** The cold inlet, hot outlet and relief valve line all carry metal joints that see heat and movement.
- **Fixture stops and supply lines.** The small valves and flexible lines under sinks and behind toilets are small, inexpensive parts that wear out on their own schedule.

## A walk-around for an older building

With a flashlight, follow the water from where it enters to where it is used. Check the main valve where the supply comes in, in line with the sidewalk meter, then every exposed run in the garage, basement or crawlspace. Look for damp joints, rust stains, white or green crust and water marks on the framing below. Open the cabinets under each sink and check the stops and supply lines, look behind each toilet, and check the floor and pan around the water heater. Upstairs, look at ceilings under bathrooms for stains. The [guide to identifying pipe material](https://hilltoprepipesanfrancisco.com/guide/how-to-identify-pipe-material/) helps name what you find.

## One leak, or the pipe

One leak at one joint is a repair. A pattern is different: leaks at different joints along the same galvanized run, rusty water after the house sits, and flow that keeps dropping at several fixtures say the pipe itself is wearing out, and patching each joint as it fails can end up costing more than replacing the run. With copper, several pinholes on the same run point at that run. The [repipe vs repair guide](https://hilltoprepipesanfrancisco.com/guide/repipe-vs-repair/) walks through the decision, and [whole-house repiping](https://hilltoprepipesanfrancisco.com/whole-house-repiping/) covers what replacement involves.

## If the leak is concealed

A leak inside a wall or under the ground can still earn bill relief. SFPUC’s leak allowance ordinarily credits 50% of the excess water for a visible leak and 100% for a concealed one, for no more than two billing periods. Owners apply within 15 days of first noticing the high bill, only after the repair, with proof such as a plumber’s invoice or an SFPUC inspection; repair costs themselves are not reimbursed. That 15-day window is a reason to find a hidden leak quickly rather than wait.

If a pipe bursts, close the main valve first; SFPUC notes most are outside or just inside the house in line with the sidewalk meter. Hilltop Repipe San Francisco arranges 24/7 emergency pipe repair for burst and leaking pipes, and the [burst pipe guide](https://hilltoprepipesanfrancisco.com/guide/burst-pipe-what-to-do/) covers the first minutes.

## Daly City and South San Francisco

Outside the city, the utility rules change. In Daly City, the Department of Water and Wastewater Resources will turn water off at the meter around the clock and asks owners not to operate the meter themselves. In South San Francisco, Cal Water is responsible only on its side of the meter and requires customer-side leaks to be repaired within five business days of its notice; SFPUC’s leak allowance does not apply there. The walk-around above works the same in either city.

## Questions about this post

### When is Fix a Leak Week?

Every March. The EPA's WaterSense program sets the exact week each year, so its site has the current dates. Nothing in a leak check depends on the calendar, though: the meter-data test and the walk-around in this post work in any week.

### What does a leak at SFPUC's alert threshold cost in a month?

Roughly $233. A leak of about 7.5 gallons an hour, SFPUC's alert threshold, wastes about 5,400 gallons over 30 days, and at SFPUC's current single-family water and wastewater rates, for a household already past the first tier, that adds about $233 to the monthly bill. Rates are reset each fiscal year, so the figure moves.

### Which joints in older water pipe tend to leak first?

In galvanized steel, the threaded joints, where the wall is thinnest and corrosion from the inside breaks through first. In copper, pinholes in the tube wall and soldered joints. Where copper meets steel without a dielectric fitting, the steel side of that joint corrodes faster and tends to leak before the rest.

## Keep reading

- Learn [What does an SFPUC leak alert mean?](https://hilltoprepipesanfrancisco.com/guide/sfpuc-leak-alert/)SFPUC watches every San Francisco meter hour by hour and writes when water never stops flowing. What sets the alert off, how to check it yourself without touching the meter, what it costs to ignore and how to get part of the bill back.
- Learn [What should you do when a pipe bursts?](https://hilltoprepipesanfrancisco.com/guide/burst-pipe-what-to-do/)The first ten minutes decide how much damage a burst pipe does. Where San Francisco shutoffs usually are, what not to touch, who to call in the city and in San Mateo County, and what happens after the water stops.
- Learn [What causes pinhole leaks in copper pipes?](https://hilltoprepipesanfrancisco.com/guide/copper-pinhole-leaks/)There is no single cause. Water chemistry, flow speed, workmanship, sediment and electrical conditions can each thin a copper wall until it opens, and where the leaks appear is the most useful clue to which one is at work.
- Decision Guide [Repipe vs repair: when is a full repipe worth it?](https://hilltoprepipesanfrancisco.com/guide/repipe-vs-repair/)A repair fixes a defect. A repipe replaces a material that is failing everywhere. The work is telling the two apart, and the evidence is in the pipe, the pattern of leaks and the flow.
- Learn [How can you tell if you have galvanized pipes?](https://hilltoprepipesanfrancisco.com/guide/how-to-identify-pipe-material/)A flashlight, a magnet and a coin answer most of it. What you find decides which questions matter next, and what shows in the garage is not always what runs inside the walls.