Who owns the water service line in Diamond Bar, CA
Which part of the pipe is yours
Yours from the meter to your building
Why, and what to doYours all the way to the main under the road
Why, and what to do
If something’s wrong
Who to call first about the water service line
Who is responsible for which part
Walnut Valley Water District owns the service line up to the meter and fixes its own equipment, and the customer has the line from the meter to the home. The District's answer to who is responsible for leaks and repairs is that "Customers are responsible for leaks on their property, including the line between the meter and the home," and that "WVWD is responsible for fixing leaks on District-owned equipment, such as the meter itself." This is Walnut Valley Water District's own statement.
- Walnut Valley Water District
- The service line from the District's main to the meter, and the meter. The District's Rules and Regulations define the permanent water service line as the District's facility between its distribution mains and the water service connection, and make services the District's property on its acceptance of them for operation, maintenance and repair.
- The property owner
- The line between the meter and the home, and leaks anywhere on the property.
What else is worth knowing
Sources
Walnut Valley Water District, Frequently Asked QuestionsWhat Walnut Valley Water District reported to the State about service-line materials
Federal rules required every community water system to inventory its service lines and publish the result. These are the figures this one filed.
The inventory records what each line is made of: lead, galvanized requiring replacement, non-lead, or lead status unknown. “Still unclassified” counts the lines whose material has not been identified. It does not mean they are lead.
Walnut Valley Water District has classified more of its service lines than most of California: 0.00% of its lines are unclassified, against 9.2% statewide.
- 27,655
- 0 (0.00%)
What this page cannot tell you
- This describes who is responsible for which part of the pipe. It is not a record of what your own service line is made of.
- The State's service area map puts effectively all of Diamond Bar's land inside the boundary it maps for Walnut Valley Water District. Measured 25 Sep 2026.
- Classified does not mean inspected. Across California only 22% of service lines were established by field inspection; most of the rest come from records, the year of construction, or a predictive model.
- These figures were submitted to the State by the water system itself and were read on 4 Sep 2026. They may not reflect its current inventory - ask the water system to confirm anything about a specific address.
Your other pipe: the sewer lateral
For the sewer lateral, Diamond Bar gives the opposite answer to the one above:
In Diamond Bar the whole house lateral is the owner's, including the part under the street. The City's code provides that "All house laterals ... shall be maintained by the owner of the property served in a safe and sanitary condition", and Los Angeles County Public Works, which maintains the mainline sewers, says that "The private property owner is responsible for the entire length of the lateral, which includes that portion that may be located within the public right of way (under the asphalt and street landscaping)."
Your sewer lateral is yours to the main; your water line stops being yours at the meter.
Who pays for the sewer lateral in Diamond Bar, CALook up a specific address
This page describes what applies to properties in Diamond Bar in general. To see which authorities serve one address, and what records exist for it, search for it.
Search for an addressHow this compares across California
- Why your two pipes disagree — the places where the sewer and water authorities contradict each other about the run beneath the road.
- Which water systems know what is buried — how much of each California system’s network the utility can actually identify.