# Partial Repiping in San Francisco

> Partial repiping in San Francisco: hot-side, branch, floor or single-unit replacement, the joints between new and old pipe, slab leak reroutes and what stays.

URL: https://hilltoprepipesanfrancisco.com/partial-repiping/

A defined part of the supply system replaced, such as the hot side, one floor, one bathroom group or one flat, with the old pipe that stays written down.

Last Updated: October 30, 2026

- **606.3** San Francisco code section requiring shutoffs in each dwelling unit, so one flat can be worked on without cutting off the others
- **100%** SFPUC leak allowance on excess water from a concealed leak, behind a wall or underground, once it is repaired and documented
- **15 days** Window to apply for an SFPUC leak allowance after first notice of a high bill
- **$259** DBI re-inspection fee per half hour, charged when an inspection fails or an extra one is needed

A partial repipe replaces one defined part of a building’s supply system and leaves the rest in service: the hot side, one floor, one riser, one bathroom group or one flat in a building. [Hilltop Repipe San Francisco](https://hilltoprepipesanfrancisco.com/) offers and manages partial repiping across San Francisco, Daly City and South San Francisco, with the work carried out by licensed and insured contractors under a plumbing permit and city inspection. When the failure turns out to be system-wide, the same visit can scope a [whole-house repipe](https://hilltoprepipesanfrancisco.com/whole-house-repiping/) instead.

The defining feature of a partial repipe is what it leaves behind. A good scope says exactly where the new pipe starts and stops, what material sits on the other side of each joint, and what condition that old pipe is in. “Part of the house was repiped” means little to a later buyer, inspector or plumber; a written boundary means a great deal.

## What happens on the first visit

The visit starts like any repipe, at the meter box and the main valve, with static pressure measured. Then the trouble is located. A run of pinholes on one copper line, a bathroom with weak flow on one floor and a leak under a garage slab are three different problems, and each suggests a different boundary. The pipe on both sides of the trouble is identified, because a partial repipe only works if the pipe that stays is sound.

The visit looks especially hard at what is upstream. If the new section will be fed through old galvanized steel, the rust and the low flow will keep coming. If the old pipe outside the boundary is copper in good shape, a partial job can be a lasting fix. The result is a written scope naming the boundary, the material, the transitions, each opening and who patches it.

## Where the boundary goes

### Hot side only

The hot lines in an old system often fail before the cold, because heat speeds corrosion. Replacing the hot side from the water heater to each fixture is a common partial repipe. It usually follows the same route as the cold lines, so the openings are planned with the possibility that the cold side follows later. The scope records that the cold side is old pipe and remains in service.

### Cold side and branch-only replacement

Sometimes the cold side, or one branch to one fixture group, is the problem: a kitchen line that was patched three times, a branch to a laundry added in a different era. A branch replacement runs from the trunk to the fixtures it serves and leaves the trunk in place. It fits when the trunk is sound copper. It is a poor fit when the trunk is the narrowed galvanized line starving every branch.

### One floor or one bathroom group

In a two- or three-story house, a top-floor bathroom group can be replaced from its riser upward, or one floor can be replaced from a valve at the riser. This is often the scope when that floor is being remodeled, which the [repiping during renovation](https://hilltoprepipesanfrancisco.com/repiping-during-renovation/) page covers.

### One flat in a shared building

In San Francisco flats and apartment buildings, a partial repipe is often one unit. The city’s code requires shutoffs in each dwelling unit so its hot and cold supply can be turned off without interrupting the others, and any unit that is remodeled has to be brought up to the city’s valve rules. DBI requires a separate permit for each condo and apartment unit. Shared risers stay the building’s responsibility; the [apartment building repiping](https://hilltoprepipesanfrancisco.com/apartment-building-repiping/) and [condo repiping](https://hilltoprepipesanfrancisco.com/condo-hoa-repiping/) pages cover how unit work and riser work divide.

## The joints between new and old pipe

Every boundary has joints, and they are where a partial repipe is won or lost. Where new copper meets remaining steel, San Francisco’s code requires a dielectric or insulating fitting, or a brass nipple at least 6 inches long, to stop galvanic corrosion at the joint. Where PEX meets old pipe, the transition is a listed fitting from the PEX system in use. A valve at the boundary, where there is room for one, makes the next stage of work simpler.

The new section is pressure tested before it is concealed, at working pressure with water or at 50 psi with air for at least 15 minutes. The old pipe outside the boundary is not part of that test, which is another reason the scope should describe its condition rather than imply it is new.

## Slab and under-floor leaks: reroute or repair

Where a supply line runs in or under a concrete floor, such as a ground-floor garage slab, an addition on grade or a house built on a slab, a leak under the concrete shows as a warm spot on the floor, a meter that turns with every tap closed, or water at the base of a wall. Whether a particular house has pipe under concrete is found on the walk-through; it varies with how and when the house was built.

There are two ways to deal with it. A reroute abandons the leaking line where it lies and runs a new one overhead, through a garage ceiling, a wall or a soffit, so nobody breaks concrete. A repair opens the slab at the leak and replaces the damaged section. Rerouting is usually the first choice because it avoids jackhammering and replaces a whole run rather than a few feet. Where new pipe must go under a slab, the California code asks for copper installed without joints where possible, with brazed joints where needed, and PEX placed in soil must be sleeved. Finding the leak precisely comes first, which the [water leak detection](https://hilltoprepipesanfrancisco.com/water-leak-detection/) page covers. An active leak flooding a floor is an emergency, and [emergency pipe repair](https://hilltoprepipesanfrancisco.com/emergency-pipe-repair/) is available 24/7 for burst pipes and leaks that cannot wait.

San Francisco owners have a billing reason to document the repair. SFPUC’s leak allowance can credit 100% of the excess water from a concealed leak, behind a wall or underground, compared with 50% for a visible one such as a running toilet. The application is due within 15 days of first notice of the high bill, is granted only after the repair, and needs proof such as a plumber’s invoice. The [SFPUC leak alert guide](https://hilltoprepipesanfrancisco.com/guide/sfpuc-leak-alert/) explains the alerts that often flag these leaks first.

## When a partial repipe stops making sense

A partial repipe makes sense when one part of the system is clearly worse than the rest. It stops making sense when the same pipe is failing in several places, when galvanized steel stays upstream of the new section, or when the walls being opened are the same walls a later whole-house repipe would open. Each stage needs its own visit, permit, transitions and patching, and homeowners report going room by room to spread out the cost, which pays those fixed costs again at every stage. The [repipe vs repair guide](https://hilltoprepipesanfrancisco.com/guide/repipe-vs-repair/) covers the decision, and the [copper pinhole leaks guide](https://hilltoprepipesanfrancisco.com/guide/copper-pinhole-leaks/) covers whether a run of pinholes is local or system-wide. For a single leak with sound pipe around it, [pipe repair](https://hilltoprepipesanfrancisco.com/pipe-repair/) may be all that is needed.

## Permit and cost

DBI requires a permit before pipe is cut into or replaced. San Francisco’s code exempts only leak repairs that do not cut or remove piping and swaps of faucets, angle stops and hose bibbs. The category DBI assigns to a partial repipe depends on the building and the scope: the single-unit category is $290, and the house categories are $549, or $809 with underground work such as a slab reroute below grade. Re-inspections cost $259 per half hour.

There is no published local price range for a partial repipe that holds up, so it is priced from its drivers: the length and number of runs, the fixtures fed, access, the walls opened, the transitions, the permit and the patching. The [repipe cost guide](https://hilltoprepipesanfrancisco.com/guide/repiping-cost/) shows how those drivers move a price, and the [guide to how invasive repiping is](https://hilltoprepipesanfrancisco.com/guide/how-invasive-is-repiping/) shows what the openings look like.

## What's included

- A written boundary: which runs are replaced and which old pipe stays, by location and material
- Static pressure at the main valve, and the condition of the pipe on both sides of each tie-in
- New PEX or copper within the boundary, sized for the fixtures it serves
- Listed transition or dielectric fittings at every joint between new and retained pipe
- Isolation valves at the boundary where they help future work
- Fixture stops and air chambers on every fixture the new section feeds
- Pressure test of the new section, a flush, and the permit and inspection before walls close
- A list of each opening and who patches it

## Repair, partial repipe or whole house

|  | Repair a section | Partial repipe | Whole-house repipe |
| --- | --- | --- | --- |
| What is replaced | A few feet at the leak | A defined run, floor, side or unit | Every supply line from the main valve |
| Fits when | The pipe around the leak is sound | One part of the system is failing and the rest is sound | The same pipe is failing throughout |
| Old pipe left | Nearly all of it | Everything outside the boundary, listed | Only the service line, unless it is included |
| Transitions | Two | One at every boundary joint | Few or none |
| Permit in San Francisco | None if no pipe is cut or removed; otherwise yes | Yes | Yes |

## Related resources

- Decision Guide [Repipe vs repair: when is a full repipe worth it?](https://hilltoprepipesanfrancisco.com/guide/repipe-vs-repair/)A repair fixes a defect. A repipe replaces a material that is failing everywhere. The work is telling the two apart, and the evidence is in the pipe, the pattern of leaks and the flow.
- Learn [What causes pinhole leaks in copper pipes?](https://hilltoprepipesanfrancisco.com/guide/copper-pinhole-leaks/)There is no single cause. Water chemistry, flow speed, workmanship, sediment and electrical conditions can each thin a copper wall until it opens, and where the leaks appear is the most useful clue to which one is at work.
- Learn [What does an SFPUC leak alert mean?](https://hilltoprepipesanfrancisco.com/guide/sfpuc-leak-alert/)SFPUC watches every San Francisco meter hour by hour and writes when water never stops flowing. What sets the alert off, how to check it yourself without touching the meter, what it costs to ignore and how to get part of the bill back.
- Learn [How invasive is repiping a house?](https://hilltoprepipesanfrancisco.com/guide/how-invasive-is-repiping/)A repipe opens walls in planned places, not along every pipe. Where the old lines run, what the walls are made of and how the building is stacked decide how many openings there are and how much patching follows.
- Cost Guide [How much does it cost to repipe a house in San Francisco?](https://hilltoprepipesanfrancisco.com/guide/repiping-cost/)Typical San Francisco-area ranges for a whole-house repipe by number of baths, what sits inside the price, the permit fees by city, the programs that help and why two quotes for the same house can differ.

## How a repipe runs

1. The call Describe the building Building type, floors, number of baths and units, the pipe you can see in the garage or basement, and what you have noticed.
2. Walk-through Map the pipe The supply is traced from the meter: pipe map, wall types, the main valve, the water heater and where access is easiest.
3. Scope Written scope and price Material, layout, every planned opening, the permit and who patches what, on paper before work is booked.
4. The work Permit, new lines, pressure test The permit is filed, new lines are run while the old ones still serve, fixtures are switched over and the system is pressure tested.
5. Sign-off Inspection, then patching The city inspector signs off with the pipe still visible. Then the openings are closed.

## What this work looks like

New PEX lines to stop valves for a sink and toilet in an opened bathroom wall of a San Francisco flat

New red PEX hot line beside an older copper line across San Francisco garage joists

New ball valve where older copper meets new copper on a San Francisco garage ceiling

Capped old copper stub at the floor and a new blue PEX line down the wall to a washer valve box

## Partial repiping questions

### Can just the hot water lines be replaced?

Yes. Replacing the hot side from the water heater to each fixture is a common partial scope, because heat speeds corrosion and the hot lines in an old system often fail first. The cold side stays, so the scope should say so plainly, and every joint where new hot pipe meets old metal gets a listed transition.

### Will a partial repipe stop rusty water?

Only if the rust comes from the part being replaced. If galvanized steel stays upstream, such as the trunk in the garage or the service line, it keeps shedding rust into the new pipe and the fixtures. Tracing which runs are steel before setting the boundary tells you whether a partial job can solve it.

### Is a slab leak rerouted or repaired in place?

Usually rerouted. The leaking line is abandoned under the concrete and a new one is run overhead, through a garage ceiling, a wall or a soffit, which avoids breaking the slab and replaces the whole run. Repairing in place means opening the slab at the leak, and it fits when rerouting is impractical. A second leak on lines of the same age points toward a wider repipe.

### Does replacing one bathroom's supply lines need a permit in San Francisco?

Yes, if pipe is cut into or removed, which replacing supply lines always involves. San Francisco's code exempts only leak repairs that do not cut or remove piping and swaps of faucets, angle stops and hose bibbs. DBI assigns the permit category, and the inspector sees the new pipe before the wall closes.

### How is a partial repipe priced?

By what is replaced and how hard it is to reach, not by a published local range. The length and number of runs, the fixtures fed, the walls opened, the number of transitions to old pipe, the permit and the patching set the price. A partial job that will be followed by another can end up costing more than one whole-house repipe.

## Related services

### Whole-house repiping

Every hot and cold supply line from the main valve to each fixture, in PEX or copper, tested and inspected.

Whole-house repiping

### Water leak detection

Hidden supply leaks located by isolation and testing, so the wall that gets opened is the right one.

Water leak detection

### Pipe repair

Water leak, burst pipe and copper pipe repair on supply lines, with the permit question answered before the wall closes.

Pipe repair