Septic to Sewer Conversion in the San Fernando Valley: The Sewer Side of the Job

November 9, 2026 • BBC Rooter & Plumbing

Most people are surprised to hear there are still septic tanks in the San Fernando Valley. The Valley floor was sewered decades ago, and if you live in Reseda or Van Nuys the idea sounds like something from a different county. But the sewer mains were built outward and upward from the center, and they stopped where the subdivisions stopped. The properties that got built before the main reached their street went in on a tank and a seepage pit, and some of them are still on one.

The pockets we see most often are parts of Sylmar above Foothill Boulevard, Shadow Hills and Lake View Terrace, the upper end of Chatsworth out toward Browns Canyon, hillside streets in West Hills, and higher lots in Encino and Bel-Air that predate the main coming up the road. Properties on two-thirds of an acre with a horse setback and a long gravel driveway are the typical profile.

Why People Convert

Nobody converts for fun. There are four reasons it comes up, and they arrive in roughly this order of urgency.

• The system failed. The leach field stopped percolating, the tank is backing up into the house, or there is effluent surfacing in the yard. This is the version with no planning time.
• A main finally reached the street. Once a sewer is available in front of the property, connecting becomes possible and in some cases required.
• A remodel or an ADU. Adding fixtures or a second dwelling pushes the load past what the existing tank and field were sized for. That often makes the conversion cheaper than enlarging the septic system.
• A sale. A septic system is a line item a buyer's agent will push on, and a failed one can hold up escrow the same way a failed sewer inspection does.

Two Jobs, Two Contractors

A conversion is two separate pieces of work, and homeowners routinely price it as one.

The sewer side is a new building sewer from the house out to the city main, the tap at the main, a two-way cleanout, and rerouting the house drain so it heads for the street instead of the tank. That is underground pipe work and it is what we do.

The tank side is pumping the tank out and permanently abandoning it under Los Angeles County Environmental Health rules. In practice that means pumping it dry and then either crushing the tank and backfilling the void or filling it with sand or slurry so it cannot collapse under the yard later. BBC Rooter does not pump septic tanks and does not design or install leach fields. That work goes to a licensed septic contractor, and we are used to sequencing around one.

Leaving a tank in the ground unpumped and unfilled is the shortcut that shows up years later as a sinkhole in a lawn. We have camera work on properties in Chatsworth and the Encino hills where a house was connected to the sewer at some point in the past and the old tank was simply forgotten.

The Order of Operations That Keeps the House Livable

Done in the right sequence, a conversion does not put the household out of service for more than a few hours.

1. Locate and verify. Find the city main, confirm its depth and invert elevation, and camera the existing house drain. This is the step that decides whether the rest of the plan is possible.
2. Permit. A sewer permit for the connection, a street cut permit if the trench enters the roadway, and the county filing for the tank abandonment.
3. Build the new line. Trench, bed, lay and grade the new lateral from near the house out to the main, set the cleanout, and make the tap. The house stays on the tank through all of it.
4. Switch over. Cut the house drain away from the line to the tank and tie it into the new lateral. This is the short window where drains are down.
5. Abandon the tank. Pump and fill or crush, inspected and signed off.

Doing step five before step four is how a family ends up in a hotel.

What the new line is built from

A new building sewer in the City of Los Angeles is normally 4-inch ABS or PVC in solvent-welded lengths, bedded on sand or crushed rock and backfilled in lifts so the pipe is not left bridging a void. At the main, the tap is made with a saddle or a new wye depending on what the main is made of. A cast iron or vitrified clay main is tapped differently than a modern PVC main, and the crew needs to know which is under the street before the day of the connection. Trench walls past roughly five feet of depth get shored. On the deeper mains in Sylmar and upper Chatsworth, where the invert can sit eight or nine feet down at the tap, shoring and spoil handling become a real part of the day's work.

What Actually Sets the Cost

Distance and depth do most of the work in that number. The run from the house to the main sets how much trench there is to dig, and the depth of the main at the tap sets how hard that trench is and whether it needs shoring. Everything else is a modifier.

Available fall matters next. A building sewer wants a quarter inch of drop per foot, so a 150-foot run to the street needs roughly three feet of elevation between the house connection and the main. Flat lots with a shallow main are where this gets tight.

Then the route. Driveway, patio, retaining walls and mature trees all add either restoration cost or a longer path around them. A street cut brings its own permit and a pavement restoration spec that varies by jurisdiction. And on hillside properties where the usable ground sits below the street, gravity to the main may not exist at all, in which case the design needs a sewage ejector pump in a sealed basin instead. A pumped system is a different job with a different number, and on a hillside conversion it is the single biggest swing factor in the price.

The honest version of a quote on this work requires somebody to locate the main and read its invert first. A price given over the phone from an address is a guess about three feet of elevation nobody has measured.

The Old Pipe to the Tank Is Usually Not Reusable

There is a hope on most of these jobs that the existing line from the house can be extended to the street and save some trench. It rarely survives the camera. A line to a tank in the yard was short, often shallow, and laid at whatever grade got it there, because it never had to reach a main under a road. On properties old enough to have a tank, the material is commonly vitrified clay in short mortared sections, or Orangeburg, the tar-impregnated fiber pipe used from the mid-1940s into the early 1970s that deforms into an oval and holds no shape. Neither is something to build a new connection on.

Sylmar has one more wrinkle. The 1971 Sylmar earthquake and the 1994 Northridge earthquake both moved ground hard in that part of the Valley, and old rigid pipe in those neighborhoods frequently shows pulled joints rather than cracks. A line can look intact on a flow test and still be offset at three joints.

If the ADU Is the Reason

When the conversion is being driven by a new unit, the two projects should be designed together and trenched together. The excavation is the expensive part of sewer work, and the route to the street serves both. We cover the connection decisions for a second dwelling in ADU sewer connections in Los Angeles, and the same rule applies here: open the ground once.

BBC Rooter & Plumbing handles septic-to-sewer connections and new building sewers in Sylmar, Chatsworth, West Hills, Granada Hills, Mission Hills, North Hills, Northridge, Encino and across the San Fernando Valley. Locating, trenching, new laterals, cleanouts and main taps. Licensed contractor CSLB #720343. Call 818-280-9135, or read our frequently asked questions.