Why Is My Pasadena Water Bill So High? The Most Likely Reason Nobody Mentions

Published by Pasadena Leak Detection · Updated August 2026 · 7 min read

You opened your Pasadena Water and Power bill and stopped. The number on the page is $200, $350, maybe $500 more than last month — with no obvious explanation. Same household size. Same routines. No pool. No garden hose left running. You checked everything you could think of, and nothing adds up.

This is one of the most common situations Pasadena homeowners call us about. And in the majority of cases, the answer is the same: a hidden water leak somewhere in the plumbing system — most commonly a slab leak or in-wall pipe failure.

Not a dripping tap or a running toilet — something you can’t see. A pinhole breach in a copper pipe behind a wall, a slow crack in a supply line beneath the concrete slab, or a fracture in the underground service line between the PWP meter and your house. These leaks run continuously, 24 hours a day, losing water that your meter faithfully records but that never reaches a tap or toilet.

The Pasadena Factor: Why Hidden Leaks Are More Common Here Than Most of LA

Pasadena doesn’t have an average water leak problem. Three specific, compounding factors make hidden pipe failures significantly more common in this city than in newer parts of Los Angeles County:

1. The Age of the Housing Stock

Approximately 65% of Pasadena’s residential housing was built before 1970. Bungalow Heaven, Garfield Heights, Madison Heights, parts of East Pasadena, Hastings Ranch, and most of Northwest Pasadena all date from the 1900–1970 construction window. The plumbing systems in these homes — galvanized steel supply lines in pre-1950 properties, copper supply lines in mid-century construction — are now 55 to 125 years old. No residential plumbing material was designed to last that long without significant maintenance or replacement.

2. Pasadena’s Extremely Hard Water

Pasadena Water and Power delivers water from the Raymond Basin groundwater and Metropolitan Water District imports at a hardness of 12.5 to 15.2 grains per gallon (GPG). For reference:

At Pasadena’s hardness level, calcium and magnesium deposits accumulate inside copper pipes while simultaneously creating the electrochemical conditions for pitting corrosion — microscopic holes that form in the copper wall and deepen under normal water pressure until they breach the pipe entirely. This is why copper pinhole leaks are the single most common hidden leak type we find in Pasadena homes.

3. Alluvial Soil and Seismic Activity

Pasadena sits on alluvial soil — river-deposited sediment that expands significantly when saturated and contracts during dry periods. Pasadena’s concentrated rainfall pattern (75–80% of the annual 20 inches falls between November and March) means the soil beneath homes goes through a significant expansion-contraction cycle every year. For copper pipes embedded in concrete slabs — the standard construction method from 1945 to 1975 — this cyclical soil movement stresses the pipe at joints and elbows, eventually causing stress fractures that become slab leaks.

How to Check If You Have a Hidden Leak Right Now

The most reliable DIY test takes about 35 minutes and requires nothing except access to your PWP meter:

1. Turn off everything: Every tap, toilet (hold the float arm up after it fills), dishwasher, washing machine, ice maker, irrigation system, and all outdoor hose bibs. Everything that uses water must be off.
2. Find your PWP meter: It’s in a concrete box near the street curb at the front of your property. Lift the lid and look for the meter display.
3. Look for the leak indicator: Most PWP meters have a small triangle or star-shaped dial on the face. If it is rotating or moving, water is flowing somewhere in your system despite everything being off.
4. Record the reading and wait: Write down the exact meter reading and the time. Do not use any water for 30 minutes. Check the reading again. If the numbers changed — even slightly — you have a confirmed hidden water leak somewhere in your plumbing.

The Four Most Common Sources of Unexplained PWP Bill Increases in Pasadena

What to Do After Confirming Your Meter Is Moving

If the meter test confirms a leak, here is what to do:

1. Check the obvious first: Walk through your home looking for visible drips, wet spots, or a running toilet. Add food colouring to each toilet tank and check for colour in the bowl without flushing. Check all hose bib connections and the irrigation system shut-off.
2. If nothing obvious: Call a licensed leak detection specialist in Pasadena. Do not attempt to probe walls, lift flooring, or access the slab yourself. Unauthorised access work can void your homeowner’s insurance claim for the repair and creates structural access damage that may not be at the actual leak location.
3. Document everything: Photograph the meter reading. Gather your last 3 PWP bills. These are needed for your PWP Water Leak Assistance Program application and your homeowner’s insurance claim.

About the PWP Water Leak Assistance Program

If your high water bill was caused by a hidden leak, Pasadena Water and Power offers a Water Leak Assistance Program bill credit of up to $3,000 through their Water Leak Assistance Program. To qualify, you must apply within 30 days of discovering and repairing the leak. A professional leak detection report documenting that the leak was hidden is part of the application evidence.

Apply at pwp.cityofpasadena.net/water-leak-assistance-program or call PWP at (626) 744-4005. The annual program fund is limited — apply as soon as possible after repair.

When to Call a Professional vs. Handle It Yourself

Call a licensed leak detection specialist when the meter test confirms a leak and you cannot find a visible source. Professional detection equipment — acoustic sensors, thermal imaging cameras, pressure testing gauges — finds hidden leaks that no DIY method can locate without causing significant structural damage in the process.

Handle it yourself if the meter test confirms the leak AND you find a visibly dripping connection, a running toilet, or an accessible fixture leak. These can be addressed with standard plumbing repairs without detection equipment.