Plumbing for Remodels, Additions and ADUs in Los Angeles and Across Southern California

Remodel plumbing is the repiping, drain and vent, water heater, gas line and sewer work that a kitchen, bathroom, room addition, whole-home renovation or ADU needs to pass inspection and work for decades. Green Design and Build (CSLB #1110975, licensed general building contractor) plans and supervises that work as part of your project, serving homeowners across Los Angeles County, Orange County, Ventura County, western Riverside County and western San Bernardino County; the plumbing itself is performed by licensed plumbers and scheduled and supervised by us as your general contractor.

We do not run a service-call plumbing business; if you need a drain cleared tonight, call a plumber.

Repiping galvanized homes with copper or PEX

Most Valley, Glendale, Burbank and older Orange County houses built before the mid-1960s were plumbed with galvanized steel, and many 1970s and 1980s homes have copper that is now pinholed. A remodel is the cheapest time to repipe because the walls are already open and the patching is already in the budget.

The California Plumbing Code recognises both copper and PEX for water distribution (CPC Table 604.1). Type L copper is rigid and lasts 50 years or more; PEX is faster, needs fewer joints and costs less, but cannot be exposed to sunlight. We typically specify PEX for concealed runs and copper where piping is exposed or the homeowner prefers it. Two details come with every repipe: if static pressure is above 80 psi, common on hillside and Valley lots, the code requires a pressure regulator with an expansion tank (CPC 608.2); and if the house was built before 1994, Civil Code 1101.4 (SB 407) requires any remaining toilets above 1.6 gallons per flush, showerheads above 2.5 gpm and faucets above 2.2 gpm to be replaced before the permit is finaled.

Moving drains: slab versus raised foundation

Where the toilet goes is the most expensive decision in a bathroom. A toilet needs a 3-inch drain, and horizontal drain piping under 4 inches must fall at least one-quarter inch per foot (California Plumbing Code as applied by LA County Building and Safety), which limits how far a toilet can move before the drain no longer meets the existing stack. On a raised foundation a plumber can usually do that in a day or two from the crawlspace. On a slab the floor is saw-cut and trenched, the new drain set and inspected, and the concrete re-poured, which is why slab relocations cost two to three times as much. Layouts also have to respect code clearances: 15 inches from the centreline of a toilet to any side wall and 24 inches in front (CPC 402.5).

Our bathroom remodel cost guide describes a late-1980s hall bathroom budgeted at about $22,000 with the tub staying put. On day two, removing the tub surround exposed a failed tub overflow gasket that had rotted the bottom plate and subfloor and started mold; the job finished at roughly $28,500, about a week and a half late. A 15 to 20 percent contingency is how you absorb that.

Water heaters: tankless, heat pump and Title 24

Replacing a water heater in the City of Los Angeles requires an LADBS plumbing permit even when it is like-for-like, with a narrow exception for LADBS-registered contractors doing equal-capacity swaps. Every new or replacement water heater in California must be strapped or braced against earthquake movement (Health and Safety Code 19211).

Under the 2025 California Energy Code, which applies to permits applied for from January 1, 2026, a replacement in an existing single-family home can be a gas storage tank, a gas tankless unit or a heat pump water heater; an electric resistance tank is allowed only where one already exists. New and accessible existing hot water piping must be insulated, tankless units need isolation valves with flushing ports, and the plumber files the CF1R and CF2R energy forms with the permit.

The practical issues are gas and venting: a tankless unit draws several times the gas of a 40-gallon tank, so the gas branch often has to be upsized from the meter, and it needs sealed venting and a condensate drain. A heat pump water heater needs a dedicated circuit, coordinated with the electrical work, and a location with enough surrounding air, which is why a garage works and a closet usually does not. When a City of Los Angeles residential alteration permit is valued above $10,000, Municipal Code 94.1217 also requires a seismic gas shutoff valve, so we scope it up front.

Sewer line replacement

Sewer laterals in Southern California fail for three reasons: clay joints that roots have found, cast iron rusted through from the bottom, and bellied lines that hold water. Before a project adds fixtures to a line, we camera-inspect it.

Open-trench versus trenchless pricing, street-cut permits and what a camera inspection tells you are covered in our sewer line replacement cost guide.

In the City of Los Angeles the property owner is responsible for the house connection sewer from the property line to the main in the street, including root problems under the public sidewalk. Replacement on private property is an LADBS express plumbing permit; work in the public right-of-way needs a Sewer “S” Permit from the Bureau of Engineering and a Bonded Sewer Contractor. A project that adds enough fixtures or a new unit to increase flow also pays a Sewer Facilities Charge before the building permit is issued. Trenchless lining or pipe bursting spares a driveway or landscaping but needs a line sound enough to line; the camera footage decides.

ADU utility connections

Where an ADU’s water, sewer and gas come from is decided at plan check, not at the trench. Government Code 66324 says an ADU built inside existing space, such as a garage conversion, and any junior ADU cannot be treated as a new residential use for utility connection fees or capacity charges, and fees for a new detached ADU must be proportionate to its size or fixture count. Whether a detached unit ties into the house lines or gets its own service depends on the city and utility; in the City of Los Angeles we settle the LADWP and sewer questions during plan check.

On site, ADU plumbing is mostly trenching, inspected before backfill. Our ADU cost guide describes a detached ADU that grew from $180,000 to $265,000; part of that was an old clay sewer line from the main house found running almost directly under the new footprint when excavation started, rerouted at roughly $14,000. A utility locate before design would have priced that in.

Permits and inspections

An LADBS plumbing permit covers drainage, waste and vent, fuel gas, potable water and rainwater piping. Routine work is an express permit with no plan check: replacing or adding fixtures, replacing water heaters, low-pressure gas piping with up to 10 outlets, sewer repair or replacement, adding an earthquake valve, and same-size underground water pipe replacement with the old pipe left exposed for the inspector. Gas systems over 10 outlets or at medium or high pressure and water services of 2 inches or larger go to plan check. We hold the building permit, coordinate the plumbing permit with the licensed plumber performing the work, and schedule the underground, rough and final inspections in the right order with framing, electrical and drywall.

Where we do this work

Plumbing scope changes with the housing stock and the permit office. In Los Angeles County, and especially the San Fernando Valley, the typical job is a 1950s to 1970s ranch house with galvanized supply lines, a clay or cast-iron lateral and a garage water heater, permitted through LADBS or LA County; hillside lots add pressure regulators and long sewer runs. In Orange County homes are newer, slabs are the norm so drain relocations cost more, and master-planned communities add HOA and CC&R review for anything visible outside, such as tankless vents. Ventura County work in Thousand Oaks, Simi Valley and unincorporated areas often means longer laterals and septic questions on older lots. Western Riverside County, in Corona, Riverside, Murrieta and Eastvale, has newer tract housing on expansive soils where slab movement is the usual cause of drain trouble. You can see every community we serve on our service areas page.

Outdoor work that needs a gas line: Outdoor kitchens, decks and pergolas · Outdoor kitchen cost

How long the plumbing takes

Plumbing scope	Typical duration
Fixture swap in place	Half a day to 1 day
Bathroom rough plumbing, raised foundation	2 – 4 days plus inspection
Bathroom rough plumbing on slab	3 – 6 days plus inspection
Whole-house repipe	2 – 5 days plus drywall patching
Water heater replacement or tankless conversion	1 – 2 days
Sewer lateral replacement	1 – 3 days
ADU utility connections	1 – 2 weeks within the ADU build

Underground and rough plumbing inspections each have to pass before the next trade proceeds; a failed inspection can cost a week.

What remodel plumbing costs in Southern California

These are typical Los Angeles budgeting ranges, not a quote. Pricing depends on foundation type, pipe access, how far fixtures move and what the wall hides.

Plumbing scope (within a larger project)	Typical Los Angeles budgeting range
Fixture replacement in place	$500 – $2,500 per fixture, installed
Kitchen rough plumbing for a relocated or island sink	$1,500 – $5,000
Bathroom drain and supply relocation, raised foundation	$2,500 – $6,000
Bathroom drain relocation on a concrete slab	$5,000 – $12,000+
Whole-house repipe, 2–3 bathroom home (PEX low end, Type L copper high end)	$8,000 – $25,000
Water heater replacement, like-for-like tank	$2,000 – $4,000
Tankless water heater conversion	$4,500 – $9,000
Heat pump water heater	$4,000 – $8,000 before incentives
Sewer lateral replacement, private property	$5,000 – $15,000
Trenchless sewer lining or pipe bursting	$8,000 – $20,000
ADU water, sewer and gas connections	$8,000 – $25,000

Frequently asked questions

Do I need a permit for plumbing work during a remodel in Los Angeles?

Yes. In the City of Los Angeles, LADBS requires a plumbing permit for work on drainage, waste and vent systems, water piping, gas piping and water heaters, including a like-for-like water heater replacement. Neighbouring cities and LA County require the equivalent through their own building divisions.

Is it better to repipe with copper or PEX?

Both copper and PEX are approved for water distribution under the California Plumbing Code and either lasts decades when installed well. Copper is rigid and right for exposed runs; PEX costs less, installs faster with fewer joints and suits concealed runs, but cannot be exposed to sunlight.

How much does it cost to move a toilet or shower during a bathroom remodel?

Moving a toilet or shower in a raised-foundation Southern California home typically adds a few thousand dollars of rough plumbing, while the same move on a concrete slab can cost two to three times as much because the slab has to be cut, trenched, inspected and re-poured. Drain slope limits how far a toilet can move without deeper work.

Can I switch to a tankless water heater during my remodel?

Yes, and a remodel is a sensible time because the larger gas line, venting and condensate drain a tankless heater needs are easier to run while walls are open. The work is permitted and inspected through LADBS or your city, and under the 2025 California Energy Code a gas tankless unit remains an allowed replacement in an existing single-family home.

Who is responsible for the sewer line in Southern California?

In the City of Los Angeles the property owner is responsible for the house connection sewer from the house to the main in the street, including the portion under the public sidewalk. Work on private property is permitted through LADBS; work in the public right-of-way requires a Sewer “S” Permit from the Bureau of Engineering and a Bonded Sewer Contractor.

Does an ADU need its own water and sewer connection?

Under Government Code 66324, an ADU created inside existing space, such as a garage conversion, or a junior ADU cannot be treated as a new residential use for utility connection fees or capacity charges, and fees for a new detached ADU must be proportionate to its size or fixture count. Whether a detached ADU in Los Angeles shares the house’s lines or gets a separate service is decided at plan check with the city and LADWP.