A new build needs plumbing decisions long before the first fixture shows up. Drain slopes are set in the trench, supply lines are sized in the framing, and mistakes buried in concrete or hidden in a wall cost far more to fix than to plan.
This guide follows the order of work on a typical house and marks where the Town, West Valley Sanitation District and your plumber each have a say. Where a rule is not spelled out here, ask the Town building division before you pour or close anything.
How does the Los Gatos permit path start?
The Town accepts building permit applications only through its online citizen portal. It does not take them at the counter, and you must register an account before you apply.
Ask who files each permit and whose name goes on it. A contractor who suggests skipping the permit is giving advice that can come back on you at sale or insurance time.
New residential projects use their own submittal package, and additions use a different one. Ask the building division which package fits your scope, what plans it wants for the plumbing, and which inspections apply.
The Town lists weekday counter hours of 8 a.m. to 1 p.m. and an email address, building@losgatosca.gov, for questions. Fees and inspection sequences vary, so confirm them with the Town.
Planning a build and unsure who handles the sewer lateral or water service? Call (855) 575-2890 and talk it through with a licensed plumber.
Call (855) 575-2890What to settle before the first trench
Plumbing is easiest to get right when these questions are answered on paper, before anyone digs or frames.
Pre-construction plumbing questions
- Where is the sewer cleanout, and is the lateral to the main on the plans?
- Does the lowest fixture floor sit less than one foot above the nearest upstream manhole?
- Where does the water service enter, and where will the main shutoff sit?
- Will the water heater be tank or tankless, and where will it vent and drain?
- Which bathrooms, kitchens and laundry share a stack, and where can each vent rise?
- Are there old septic components on the lot that must be abandoned?
- Who is pulling the permit, the owner or a licensed contractor?
Who owns the sewer lateral on a new lot?
West Valley Sanitation District serves Los Gatos, and its code splits the lateral at the property line cleanout. The upper lateral, from the building to that cleanout, belongs to the owner. The lower lateral, from the cleanout to the public main, is district owned. Where a lateral meets a main in an easement instead of the street right-of-way, the code puts the entire lateral and its cleanouts on the owner.
Work on a private upper lateral requires a permit, according to the district. If your plans show no cleanout, the district says the owner is responsible for clearing the line all the way to the main. Put a cleanout at the property line on the plans and you avoid that problem. Near Saratoga, the district covers only about two thirds of town, so confirm which agency serves your parcel.
The district code also requires an owner-funded backflow protective device when the lowest fixture floor sits less than one foot above the nearest upstream manhole. A basement bath or a lot below street grade can trigger it. Raise the question at design stage, since a device is far easier to place before the slab is poured.
Septic to sewer conversion on an older lot
Check this before you order pipe
The Town has a permit checklist for abandoning a septic tank and connecting to the sewer, which tells us some properties in town may still have septic systems.
For a conversion, the owner must get a certificate from West Valley Sanitation District before a plumbing permit is issued, and the district may require a backflow device. The Town checklist cites the 2022 California Plumbing Code and a minimum pipe slope of one quarter inch per foot.
Water service and the meter side of the lot
San Jose Water covers Los Gatos, so your service line starts at its main and meter. The pipe between the meter and the house is a plumbing decision, and it deserves care. An undersized or poorly bedded run causes slow flow at the far bathroom.
If the lot already has a service line, decide whether to reuse it or replace it before the foundation goes in. Old galvanized steel and aging copper are cheaper to replace while the yard is open than after landscaping. On a lot up toward Lexington Hills, settle the service line route early. The plumber we send for water service line repair can tell you whether the existing pipe is worth keeping and where a new shutoff valve should sit.
What happens at rough-in and inspection
Rough-in is the stage where drain, waste, vent and supply pipes are installed but the walls are still open. Drains in ABS or PVC go in first, pitched toward the sewer. Vents rise through the roof, and supply lines in copper or PEX run to each fixture location, with stub-outs capped and labeled.
Pressure and water tests
Before the drywall goes up, the drain system is typically filled or air tested, and the supply side is pressurized so a leak shows on a gauge. Do not let a drywall crew start until you have the sign-off the Town requires. Ask the building division which tests apply.
Water heater bracing
The Town's bracing handout says a water heater needs at least two restraints, one in the upper third and one in the lower third of the tank. Each strap is fastened to a wall stud with a screw at least a quarter inch in diameter, driven at least half an inch into the wood, with a washer. Frame a solid backing board or stud where the heater will stand so those screws bite.
Who handles which part
Knowing who decides what saves phone calls.
| Part of the job | Who decides | What to do |
|---|---|---|
| Building permit | Town building division | Apply through the online portal |
| Public sewer main and lower lateral | West Valley Sanitation District | Ask the district before connecting |
| Upper lateral and cleanout | Property owner | Plan it, permit it, keep access |
| Water meter and main | San Jose Water | Contact the utility for the connection |
| Pipe in the walls and slab | Your licensed plumber | Inspect before covering |
Rules and fees change, so confirm each step with the agency involved.
What Los Gatos rules mean for your build
The Town accepts building permit applications only through its online portal, and you register an account first. Set that up before your plumber needs a permit number, or your schedule will wait on an account.
West Valley Sanitation District splits lateral ownership at the property line cleanout, so draw that cleanout on your plans. If you are converting from septic, you need the district certificate before the Town will issue a plumbing permit.
When to call a plumber during construction
Call a licensed plumber before the permit application if you are unsure of fixture counts, drain sizes or vent routes. Call again before the trench and the walls close, since a problem is cheapest to fix then. For layout help on a new bath, kitchen or laundry, talk to a team that does plumbing installation every week.
Call (855) 575-2890 if you have a leak, a failed test or a backing-up drain at any stage. We give a clear price before work starts.
New construction plumbing questions from Los Gatos owners
The Town takes building permit applications only through its online portal, so register an account first. New residential projects have their own submittal package, and the building division can tell you which one applies.
The permit carries a name, so ask who files it and whose name goes on it. Ask any plumber who suggests skipping the permit to explain why.
West Valley Sanitation District requires an owner-funded device when the lowest fixture floor sits less than one foot above the nearest upstream manhole. Ask the district about your lot before you finalize the plans.
A septic to sewer conversion needs a certificate from West Valley Sanitation District before the plumbing permit is issued. The district may also require a backflow device.
If the old line is galvanized steel or aging copper, replacing it while the yard is open is usually simpler than doing it later. On a lot up toward the mountain community of Lexington Hills, settle the service line route early. A water service line repair plumber can look at the pipe and advise.