What if the sewer main is more than 200 feet from my lot?

Does the 200-foot rule even apply to my lot?

It applies only when the city sewer is far enough away to count as not available. The state plumbing code lets the building official treat a public sewer as not available when it is more than 200 feet from the proposed building on a lot that abuts that sewer, and for houses the building official has the final say ⁷. Where no public sewer serving the lot is available in the street next to it, the drainage must go to a private sewage disposal system approved by the building official ⁸.

Two details matter for an ADU. First, the code measures to the proposed building, which for you is the backyard house, not your front door ⁷. Second, BOE's own permit notes describe the trigger as the property being more than 200 feet from a mainline ¹. If the main runs in the street in front of a Reseda house and the lot is less than 200 feet deep, the backyard house cannot be 200 feet from it. The question comes up on long flag lots, lots on private or unimproved streets, and edge-of-hillside parcels, such as some in Granada Hills. The distance that counts is the one LADBS and BOE accept on your plans, not a tape measure from the curb.

How do I find where the sewer main is and how far away it is?

Start with NavigateLA, the Bureau of Engineering's public web map, which pulls data from city departments and the county ¹⁸. The city's official sewer GIS data, kept by BOE's GIS Mapping Division, includes pipes, structures, wyes (the fitting where a house line joins the main), laterals and sewer easements ¹⁹.

A simple way to check:

1. Open NavigateLA and search your address.
2. Turn on the sewer layers and find the main that serves your block, and the wye or lateral shown for your parcel.
3. Measure from where the backyard house would sit to that main.
4. Confirm with BOE. Its plan checkers verify that a public sewer exists in NavigateLA and pull the Parcel Sewer Wye Report for the parcel, which lists its wye map numbers ⁵.

If no lateral shows for your parcel, or the main stops short of your frontage, that is worth knowing before you pay for plans. Finding it on a map before the design starts is the kind of thing a lot check settles.

Can my ADU share the house's existing sewer line, or does it need its own connection?

Often it can share. The plumbing code's default is that every building gets its own connection to a public sewer where one is available, with an exception that lets a rear building extend the front building's drain ⁹. The state's version of that code adds a note that ADUs do not need independent drainage connections when they meet the state ADU law ⁹. In Los Angeles, a sewer lateral serves one lot, so the usual pattern is the ADU's line joining the house's line on your own property before it runs to the street ¹⁶.

State law then splits ADUs into two groups:

• Conversions inside existing space, such as a garage conversion that stays within the existing walls plus up to 150 square feet for access ¹³. For these, the city cannot require a new or separate utility connection, and cannot charge a related connection fee or capacity charge, unless the unit is built with a new house or later sold separately ¹¹.
• Other ADUs, such as a new detached backyard house. The city may require a new or separate connection, and any connection fee or capacity charge must be proportionate to the ADU, based on its square footage or its drainage fixture units, and cannot exceed the reasonable cost of the service ¹².

Whether your plan checker asks for a separate line depends on the layout, slope and the condition of what is already in the ground.

What does it cost to connect if the main is far away?

If you build or extend a main, you are paying for public sewer work: BOE notes direct the applicant to get a B-permit to construct or extend the mainline and an S-permit for the wye and lateral ². Work under a sidewalk or street needs a Bureau of Engineering permit, so your everyday plumber cannot do that part alone ²⁰.

City fees come on top of construction. As of October 2026:

• Sewerage Facilities Charge (SFC): $344 per 100 gallons per day of average flow, paid before an S-permit is issued for a new house connection ⁶.
• Bonded Sewer Fee: $74 per foot of your lot's frontage, due if your property never paid into the cost of building the main it is connecting to ⁴.
• Bonded Lateral Fee: $84 per foot from your property line to the center of the street ⁴.

State law limits what can be charged to an ADU. An ADU is not treated as a new residential use when the city calculates sewer connection fees or capacity charges, unless it is built with a new house ¹¹. That rule used to be Government Code § 66324; Senate Bill 543 renumbered it § 66311.5, effective January 1, 2026 ¹⁰. Ask BOE how it applies the SFC to your ADU before you budget for it. We could not find a city statement of a set SFC amount for an ADU, so we do not quote one.

Can I use a septic system for an ADU in Los Angeles instead?

Yes, if the sewer is more than 200 feet away. BOE's procedures say the applicant may choose septic, that no SFC is then calculated, and that the septic system has to be approved by Building and Safety ¹. The plumbing code calls this a private sewage disposal system approved by the building official ⁸.

For an ADU on septic, the city may require a percolation test, which measures how fast the soil absorbs water, completed within the last five years, or within ten years if it has been recertified ¹⁴. If your house already runs on septic, the question becomes whether the existing tank and leach field can take the ADU's added flow, which is part of that same review.

Why should I put a camera down my old sewer line first?

Because you own it and you will pay for it if it fails. In Los Angeles the owner is responsible for the whole lateral, from the house to the middle of the street ¹⁵. LA Sanitation says more than half of sewer backups are caused by tree roots and by fats, oils and grease ¹⁷. That matters on an older line in Pacoima or Reseda that you have never looked inside.

The city treats the camera as standard practice when an existing house connection is extended. BOE calls a CCTV video inspection essential before it grants an extension, and if the lateral is damaged or needs replacing, a second permit is issued ³. A camera run before design tells you whether the ADU can tie into the existing line or whether a new lateral belongs in the budget.

Quick answers

Sources

1. S-Permit Processing Procedures (SFC and Bonded Sewer Fees), City of Los Angeles, Bureau of Engineering. Facts checked 2026-10-08
2. S-Permit Processing Procedures (SFC Remarks), City of Los Angeles, Bureau of Engineering. Facts checked 2026-10-08
3. S-Permit Processing Procedures (CCTV requirements), City of Los Angeles, Bureau of Engineering. Facts checked 2026-10-08
4. S-Permit Processing Procedures (Bonded Sewer Fees), City of Los Angeles, Bureau of Engineering. Facts checked 2026-10-08
5. S-Permit Processing Procedures (NavigateLA research), City of Los Angeles, Bureau of Engineering. Facts checked 2026-10-08
6. Standard and Associated Fees (S-Permits), City of Los Angeles, Bureau of Engineering. Facts checked 2026-10-08
7. California Plumbing Code § 713.4, Public Sewer Availability (2025 edition, text via GoCodebook), California Building Standards Commission. Facts checked 2026-10-08
8. California Plumbing Code § 713.2, Private Sewage Disposal System (2025 edition, text via GoCodebook), California Building Standards Commission. Facts checked 2026-10-08
9. California Plumbing Code § 311.1, HCD express terms, California Department of Housing and Community Development. Facts checked 2026-10-08
10. Senate Bill 543 (Stats. 2025, Ch. 520), chaptered text, Los Angeles County Department of Regional Planning (attachment). Facts checked 2026-10-08
11. Government Code § 66311.5 (b) and (d), State of California (text via GoCodebook). Facts checked 2026-10-08
12. Government Code § 66311.5 (e), State of California (text via GoCodebook). Facts checked 2026-10-08
13. Government Code § 66323 (a)(1)(A), as amended by SB 543, Los Angeles County Department of Regional Planning (attachment). Facts checked 2026-10-08
14. Government Code § 66323 (f), as amended by SB 543, Los Angeles County Department of Regional Planning (attachment). Facts checked 2026-10-08
15. Managing and Protecting LA's Underground Sewer System, LA Sanitation and Environment. Facts checked 2026-10-08
16. Managing and Protecting LA's Underground Sewer System (FAQ), LA Sanitation and Environment. Facts checked 2026-10-08
17. Managing and Protecting LA's Underground Sewer System (blockages), LA Sanitation and Environment. Facts checked 2026-10-08
18. Mapping Tools: NavigateLA, City of Los Angeles, Bureau of Engineering. Facts checked 2026-10-08
19. Sewer System (City of Los Angeles GIS dataset, catalog mirror of data.lacity.org), City of Los Angeles, Bureau of Engineering / GIS Mapping Division. Facts checked 2026-10-08
20. Managing and Protecting LA's Underground Sewer System (FAQ: street repairs), LA Sanitation and Environment. Facts checked 2026-10-08

Greenlight is not a contractor, architect or engineer, and this is not legal advice. Rules change; every fact here shows the date we last checked it.