Water "Will-Serve" Letter (Local Water Company / Purveyor)

The Water Will-Serve Letter: The ADU Permit Step People Always Confuse with Form 195 If you're building an accessory dwelling unit ADU in unincorporated Los...

Written by 1-800-ADU-Pros

Last updated: July 16, 2026•7 min read

Water "Will-Serve" Letter (Local Water Company / Purveyor)

The Water Will-Serve Letter: The ADU Permit Step People Always Confuse with Form 195

If you're building an accessory dwelling unit (ADU) in unincorporated Los Angeles County, somewhere in your permit checklist you'll hit two short lines under "Local Water Company": a Form 195 for Fire Flow Availability and a Will Serve Letter. They sit one on top of the other, they both come from your water company, and they get mixed up constantly. This post is about the second one — the Will-Serve Letter — what it is, how to get it, and why it is not the same thing as Form 195.

What a Will-Serve Letter actually is

A Will-Serve Letter is a short official letter from the water utility that serves your property, stating that it is willing and able to provide potable (drinking) water to your new ADU. LA County Building and Safety treats it as an agency-referral clearance: it's one of the sign-offs the County needs to see cleared before it will issue your ADU building permit. In plain terms, it's the water company telling the County, "Yes, this address can have water."

It's an availability confirmation — not a meter, not a connection, and not a bill. Any physical work or connection fees are handled separately.

Why it's not Form 195 (the part everyone gets wrong)

Here's the distinction that trips up homeowners. Both documents come from your water company, but they answer different questions:

The Will-Serve Letter confirms domestic water supply — can the utility serve drinking water to the unit.
Form 195 is the Fire Flow Availability form — it confirms how much water the hydrants near your property can deliver for firefighting (measured in gallons per minute at a given pressure). The County uses it to decide whether your ADU needs a Fire Department referral or sprinklers.

The County's own ADU Guideline lists them as two separate items, and you generally need both. Don't assume the fire-flow form covers your domestic-supply clearance, or vice versa.

One more look-alike to avoid: the LA County Sanitation Districts also run a program literally called "Will Serve." That one is about sewer/wastewater capacity and is a completely different agency. Your water purveyor's letter does nothing for the sewer requirement.

Who issues it

This is the confusing part: there's no single "LA County water office." Your issuer is whoever serves your parcel — a private water company (for example, Lincoln Avenue Water Company), a city-owned utility, or an LA County Waterworks District run by LA County Public Works. The fastest way to find yours is to look at your current water bill.

How to request it, step by step

Find your water purveyor using your water bill or by asking LA County Public Works.
Assemble the package: construction plans with your scope/project data, a site plan, a floor plan, and the completed Fire Department Form 195 (usually just the first page). Most purveyors process the will-serve request and Form 195 together.
Submit the request. Many companies accept PDFs by email; the County Waterworks Districts use their Development Services / customer-request process.
Pay the processing fee. Processing time usually starts once payment clears.
Sign as the owner. Most purveyors require the property owner to sign in person, or to submit an authorization form so a contractor or agent can sign.
Collect the letter and submit it with your plans to LA County Building and Safety.

Fees and timeline

Fees are set by each water company, not the County. Lincoln Avenue Water Company, for instance, charges $200 for the Will-Serve Letter and $200 for a Fire Flow Test. LA County Waterworks Districts publish their own rate. These are processing charges, separate from any water connection or meter fees.

On timing, the letter itself is quick — Lincoln Avenue quotes 1–3 business days for the Will-Serve Letter, but 7–10 business days if a fire-flow field test is required. LA County Waterworks generally suggests allowing about 10 business days. Because the County wants this at plan submittal or resubmittal, order it as soon as you have plans — a slow turnaround here can hold up your entire permit.

A few things that save you a trip

Building a Junior ADU (JADU)? Under state law (SB 897), a JADU isn't a separate unit for water service, so you generally don't need this letter.
The letter confirms availability only — budget separately for any new service line, meter, or connection fees. (ADUs of 750 sq ft or less are exempt from impact/capacity fees, but processing and connection charges can still apply.)
Don't wait until plan check kicks it back. Treat the Will-Serve Letter as an early errand, not a last-minute one.

Get the right letter, from the right agency, early — and this small piece of paper won't be the thing standing between you and your ADU permit.

Sources: LA County Building & Safety ADU Guideline v4.1; LA County "How To Guide for ADUs"; Lincoln Avenue Water Company Will-Serve/Fire-Flow page; LA County Sanitation Districts Will Serve Program; LA County Public Works Waterworks Development Services; California HCD ADU Handbook. Always confirm current fees and requirements with your specific water purveyor and permitting jurisdiction.

Reference card

Official number: No county form number. The Will Serve Letter is issued on the water purveyor's own letterhead. (Note: the separate "Form 195" listed alongside it is the Fire Flow Availability form, NOT the will-serve letter.)
Issuing body: Your local water company / water purveyor — e.g., a private water company (such as Lincoln Avenue Water Company), a city-owned utility, or an LA County Waterworks District (operated by LA County Public Works). The agency varies by where the property sits, not by the County permit office.
What it is: A "Will-Serve Letter" is an official letter from the water utility that serves your parcel, confirming it is willing and has the capacity to provide potable (domestic) water to your new ADU. LA County Building and Safety treats it as an agency-referral clearance — one of the "Local Water Company" sign-offs that must clear before the County will issue the ADU building permit. It documents that water supply exists for the new unit, and is separate from any physical meter or connection work.
Who needs it: Applies to new ADUs (detached, attached, or garage conversion) in unincorporated LA County permitted through LA County Building and Safety, where the water company is listed as a referral agency. You can generally skip it for a Junior ADU (JADU): under SB 897 / Government Code 65852.22(f), a JADU is not a separate dwelling unit for water, sewer, or power, so a separate water clearance is not required. Some homeowners on an existing metered connection may satisfy the County's potable-water proof with a prior water bill instead, but the will-serve letter is the standard document the ADU Guideline calls for. Incorporated cities (e.g., City of LA / LADBS) have their own process — confirm with that jurisdiction.
Fees: Fees are set by each water purveyor, not the County. As a concrete example, Lincoln Avenue Water Company charges $200 for the Will-Serve Letter and $200 for a Fire Flow Test (paid by check, Visa, MasterCard, or Discover). LA County Waterworks Districts charge their own published rate. These are administrative processing fees and are separate from water connection/meter fees. Note: under California ADU law, an ADU of 750 sq ft or less is exempt from impact/capacity fees, and connection fees for larger ADUs must be charged proportionally — but the will-serve letter processing fee itself is a service charge, not an impact fee.
Timeline: Fast for the letter itself, slower if a field test is involved. Lincoln Avenue Water Company quotes about 1–3 business days for the Will-Serve Letter and roughly 7–10 business days for a Fire Flow Test, with the timeframe starting when payment is made. LA County Waterworks Districts generally advise allowing about 10 business days or more. Request it early — it is needed at plan submittal/resubmittal, so a slow turnaround can stall the whole permit.

Requirements

Construction plans showing scope of work / project data for the ADU
Site plan and floor plan
Completed County of Los Angeles Fire Department Form 195 (Fire Flow Availability) — typically the first page — which most purveyors process together with the will-serve request
Property address / APN (Assessor's Parcel Number)
Property-owner signature (owner usually must sign in person, or submit a signed authorization form for an agent/contractor to sign on their behalf)
Payment of the purveyor's processing fee

How to file

Identify the water purveyor that serves your parcel — a private water company, a city utility, or an LA County Waterworks District. If you don't know, check your current water bill or ask LA County Public Works.
Gather the package: construction plans (with scope/project data), site plan, floor plan, and the completed Fire Department Form 195 (first page).
Submit the request to the purveyor by its required method — many accept PDFs by email (e.g., Lincoln Avenue Water Company takes them at Support@lawc.org); LA County Waterworks uses its Development Services / customer-request process.
Pay the processing fee (by phone, in person, or online depending on the purveyor). The clock on processing time usually starts when payment is received.
Have the property owner sign the letter — in person at the purveyor's office, or via a signed authorization form so an agent can sign.
Pick up or receive the completed Will-Serve Letter (and the signed Form 195 fire-flow letter, if requested together).
Submit the Will-Serve Letter with your ADU plans to LA County Building and Safety at plan submittal or resubmittal so the 'Local Water Company' referral clears before permit issuance.

Common pitfalls

Confusing it with Form 195. The Will-Serve Letter confirms DOMESTIC water supply; Form 195 is the separate Fire Flow Availability form (hydrant flow in GPM at PSI). The County's ADU Guideline lists both, separately, under 'Local Water Company.' You typically need both — don't assume one covers the other.
Confusing it with the Sanitation Districts' 'Will Serve' program. That program is about SEWER/wastewater capacity and is a different agency (LA County Sanitation Districts). The water purveyor's letter does not satisfy a sewer requirement, and vice versa.
Not knowing who your purveyor is. The issuing agency depends on your parcel's service area — check your water bill before guessing.
Leaving it to the last minute. It's a permit-issuance gate at plan submittal/resubmittal; order it as soon as you have plans.
Missing the owner-signature step. Many purveyors require the property owner to sign in person or submit a notarized/authorized signer form — plan for it if a contractor is filing on your behalf.
Assuming a JADU needs one. Under SB 897, a JADU isn't a separate unit for water service, so the clearance generally doesn't apply.
Assuming the letter means free service. It confirms availability; actual connection or meter fees (and any required new service line/meter) are billed separately.

Sources

Explore more:Permits & Feasibility

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