Understanding LADBS Chapter 6 + Non-Engineered Domestic Water Pipe Sizing
- May 21
- 4 min read
If you recently received a plumbing correction notice from the City of Los Angeles, you may have seen language like:
“If the system is designed using Chapter 6 and the Non-Engineered method, then no plan check is required and you may pull an express permit.”
For many contractors, plumbers, and property owners, this is actually good news.
The City is offering a faster and simpler path to permit approval for small plumbing projects by allowing the use of the Chapter 6 Non-Engineered Domestic Water Pipe Sizing Method.
In this article, we’ll explain:
What Chapter 6 means
What “Non-Engineered” sizing is
When you can use it
Why LADBS prefers it for small projects
How it can help avoid plan check delays
What Is Chapter 6?
Chapter 6:
refers to the water supply and distribution requirements in the Los Angeles Plumbing Code (LAPC), which is based on the California Plumbing Code.
This chapter governs:
Domestic cold water systems
Hot water distribution
Pipe sizing
Water pressure
Fixture unit calculations
Water supply demand
Traditionally, larger projects often require detailed engineered calculations using Appendix A methods. However, LADBS allows smaller projects to use simplified sizing tables instead.
What Is the Non-Engineered Method?
The Non-Engineered Domestic Water Pipe Sizing Method is a simplified sizing procedure approved by LADBS for smaller plumbing systems.
Instead of requiring a licensed engineer to perform complex hydraulic calculations, contractors can size water piping using:
Fixture unit counts
Pipe length
Available pressure
LADBS sizing tables
This method is outlined in the LADBS Information Bulletin:
IB/P/PC 2023-014 – Non-Engineered Domestic Water Pipe Sizing
The simplified approach is specifically intended for:
Tenant improvements
Small remodels
Minor fixture additions
Existing commercial spaces
Small restaurant upgrades
Retail plumbing alterations
Why LADBS Encourages the Non-Engineered Method
The City’s goal is to reduce unnecessary plan check workload for small plumbing projects.
If your project falls within the allowable thresholds, LADBS may allow:
Express permit issuance
No plumbing plan check
Faster permit approval
Simplified resubmittals
This can significantly reduce project delays.
When Can You Use the Non-Engineered Method?
Generally, projects may qualify when:
1. Fixture Unit Additions Are Small
Typically:
Less than 20 additional fixture units on the domestic water system
Examples include:
Adding sinks
Replacing fixtures
Small restroom remodels
Limited kitchen upgrades
2. Waste/Vent Fixture Units Remain Within Limits
LADBS commonly allows projects with:
Less than 216 waste/vent fixture units
to qualify for simplified permitting.
3. Existing Building Conditions Are Suitable
The method is usually intended for:
Existing buildings
Existing domestic water services
Minor modifications rather than full system redesigns
How the Sizing Process Works
The non-engineered method uses three main inputs:
Available Water Pressure
The designer must know:
Static water pressure at the site
Typical commercial buildings may range between:
45–80 PSI
Fixture Units (FU)
Each plumbing fixture has a fixture unit value assigned by code.
Examples:
Fixture | Typical Water FU |
Lavatory | 1 |
Kitchen Sink | 1.5–2 |
Toilet (tank type) | 2.5 |
Urinal | 2 |
Shower | 2 |
Service Sink | 3 |
The total fixture units determine system demand.
Developed Pipe Length
This is:
the total equivalent length from the meter
to the most remote fixture
Longer pipe runs require larger pipe sizes due to pressure loss.
Example of Simplified Pipe Sizing
Suppose a project has:
12 fixture units
60 feet developed length
55 PSI available pressure
Using the LADBS Chapter 6 sizing table:
a 3/4" domestic water line may adequately serve the system
No engineered Appendix A calculation would be required.
Why Some Projects Get Correction Notices
Many permit applicants submit:
engineered Appendix A calculations
oversized plumbing packages
unnecessary plan check documentation
When LADBS sees that the project is small enough for the simplified method, reviewers often issue a correction requesting:
Chapter 6 sizing instead
non-engineered calculations
simplified resubmittal
This is usually intended to speed up permit approval.
Common Documents Required for Resubmittal
A revised submittal typically includes:
Fixture Unit Schedule
A list of all plumbing fixtures and their fixture unit values.
Pipe Sizing Worksheet
Using LADBS non-engineered sizing tables.
Plumbing Plan Revisions
Updated drawings showing:
pipe sizes
fixture counts
water distribution layout
Developed Length Calculation
The longest piping route within the system.
Advantages of the Non-Engineered Method
Faster Permit Approval
Projects may qualify for express permits.
Lower Engineering Costs
Complex hydraulic calculations may not be necessary.
Simplified Review Process
LADBS reviewers can verify sizing quickly using standard tables.
Reduced Resubmittals
Smaller projects are less likely to receive extensive correction cycles.
When Engineered Calculations Are Still Required
The simplified method is not appropriate for every project.
Engineered calculations may still be necessary for:
Large commercial buildings
High-rise structures
Complex pressure systems
Booster pump systems
Large restaurants
Medical facilities
Extensive fixture additions
Projects exceeding fixture unit thresholds
Final Thoughts
The LADBS Chapter 6 + Non-Engineered Domestic Water Pipe Sizing method is designed to streamline permitting for smaller plumbing projects in Los Angeles.
For contractors and property owners, understanding this process can:
reduce permit delays,
simplify resubmittals,
and help projects move forward faster.
If your project qualifies, switching from engineered Appendix A calculations to the non-engineered Chapter 6 method may save both time and money while remaining fully code compliant.
You can access the Non-Engineered domestic water pipe sizing method created by City of LA through the link below:
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