# Epoxy pipe lining vs repiping: which one fixes old pipe?

> Epoxy pipe lining vs repiping for water lines: how lining works, what it can't fix, drinking water standards, San Francisco code items and when each one fits.

URL: https://hilltoprepipesanfrancisco.com/guide/pipe-lining-vs-repiping/

Decision Guide

Lining coats the inside of the pipe you have; repiping replaces it. Lining opens fewer walls, but it keeps the old pipe's layout, valves, threads and size, and in San Francisco those are often the problem.

Last Updated: October 30, 2026

Epoxy lining coats the inside of existing water pipe and can seal small leaks with fewer wall openings than a repipe. Repiping replaces the pipe, which restores full bore, removes weak threads and lets the city’s required valves and air chambers go in. Lining fits sound pipe that is hard to reach; replacement fits pipe that is failing as a material, which is the usual San Francisco galvanized case.

[Hilltop Repipe San Francisco](https://hilltoprepipesanfrancisco.com/) manages [whole-house](https://hilltoprepipesanfrancisco.com/whole-house-repiping/) and [partial repiping](https://hilltoprepipesanfrancisco.com/partial-repiping/) across San Francisco, Daly City and South San Francisco, with the work carried out by licensed and insured contractors. Lining is a different method from the one this service uses, and this guide sets out what each can and can’t do so the comparison is fair.

Key takeaways

- Lining cleans the old pipe by blasting, then coats the inside with epoxy; repiping replaces the pipe.
- A lining becomes the drinking-water surface, so the product must comply with NSF/ANSI/CAN 61.
- Lining keeps the old layout, sizes, valves and threads; a repipe can add the shutoffs and air chambers San Francisco requires.
- Lining suits pipe with sound walls in hard-to-reach places; it suits rust-thinned galvanized poorly.
- Neither method is right for every building; the pipe's condition decides.

## How epoxy lining works

Lining systems for water pipe follow the same basic steps. The building’s water is shut off and the pipes are drained. Heated air dries them. An abrasive, usually a fine grit blown through with compressed air, scours rust and scale from the inside. Then epoxy is blown or drawn through each run to coat the wall, and it is left to cure before the system is flushed and the water comes back on. The pipe is reached at fixtures, at the main and at a few access points, rather than along its length.

That access is the appeal. Where pipe is buried in a slab, encased in concrete or runs behind finishes that are expensive to disturb, lining can avoid the openings a repipe would need. Bay Area homeowners report weighing lining when a slab leak would otherwise mean jackhammering floors or rerouting over the roof.

## What lining doesn’t change

A coating changes the inside surface of the pipe. Everything else stays as it was:

- **Wall strength.** The blast removes corrosion and some metal with it. Galvanized pipe is thinnest at its threads, which is where it usually fails. A thin epoxy layer seals but does not restore the steel.
- **Size and layout.** Pipe that was undersized stays undersized, a little smaller for the coating. The trunk-and-branch route, the long runs and the dead ends all remain.
- **Valves and fittings.** Old gate valves, stops and unions are usually replaced or bypassed separately, and fittings that were already restricted keep their shape.
- **What can be inspected.** Once the walls are closed, nobody can see whether every branch and fitting was fully coated. A repipe’s new pipe is visible to the inspector before the walls close.

## Drinking water standards

The 2025 California Plumbing Code requires materials in contact with drinking water to comply with NSF/ANSI/CAN 61. With lining, the epoxy is that material. Before choosing it, ask for the product name, its certification for drinking water, the cure time and temperature it needs, and how the installer confirms the cure before the water is used. Ask also whether the work will be permitted and inspected (the [San Francisco repiping permit guide](https://hilltoprepipesanfrancisco.com/guide/san-francisco-repiping-permit/) covers the rules): DBI requires a permit before pipe is cut into or replaced, so any section replaced during lining falls under that rule.

## What a repipe adds in San Francisco

A repipe is new pipe, so it is built to current code. In San Francisco that means a fullway valve where the supply enters, a shutoff for each dwelling unit so one unit can be worked on without cutting water to the others, a control valve at each fixture, dielectric fittings or 6-inch brass nipples wherever copper meets steel that stays, and air chambers at single-handle faucets, shower valves and other quick-closing valves. A unit that is remodeled has to be brought up to the valve rules, which matters most in [apartment buildings](https://hilltoprepipesanfrancisco.com/apartment-building-repiping/). Lining keeps the old system’s valves and layout, so those items are separate work, if they are done at all.

A repipe also ends with a pressure test of the new system, with water at working pressure or air at 50 psi or more for at least 15 minutes without leakage, and a city inspection before the walls close. The [repiping guide](https://hilltoprepipesanfrancisco.com/guide/repiping-guide/) covers the full sequence.

## Galvanized, copper and slab pipe

### Galvanized

Most San Francisco repipes replace galvanized. Among 273 DataSF repipe permit descriptions from 2021 to 2025, 76 name galvanized. Galvanized at the end of its life is narrowed by rust, thin at the threads and often mixed with copper repairs. Lining is weakest in exactly that case: the cleaning step removes what was holding the bore shut, the threads stay thin, and the mixed joints stay mixed. The [guide to whether galvanized pipes are safe](https://hilltoprepipesanfrancisco.com/guide/are-galvanized-pipes-safe/) covers the condition questions.

### Copper with pinholes

Lining is more often offered for copper with pinholes, because the coating can bridge small holes. Whether that holds depends on how much wall is left and whether the cause of the pitting is still active, such as a recirculating line running too fast. The [copper pinhole leaks guide](https://hilltoprepipesanfrancisco.com/guide/copper-pinhole-leaks/) covers the causes.

### Pipe under a slab or in concrete

This is lining’s strongest case. Where a house has its water lines in a slab, the alternatives are breaking the floor or rerouting through walls, ceilings or the roof. Many San Francisco houses are built differently: where a house has living space over a ground-floor garage, as the Sunset’s builders favored, the trunk lines usually hang from an open garage ceiling, and a repipe can reach them without opening finished rooms. The [Sunset and Parkside page](https://hilltoprepipesanfrancisco.com/service-areas/sunset-parkside/) describes those houses.

## Side by side

|  | Epoxy lining | Repiping |
| --- | --- | --- |
| What happens to the old pipe | Cleaned by blasting, then coated inside | Replaced; exposed pipe removed, sealed pipe abandoned |
| Openings | Fewer, at access points and fixtures | More, planned at each route and fixture group |
| Pipe size and layout | Unchanged, slightly smaller bore | New sizing and layout, trunk-and-branch or manifold |
| Weak threads and joints | Remain, coated | Removed |
| San Francisco valves and air chambers | Separate work | Built into the scope |
| Inspection | Coating cannot be seen once closed | New pipe pressure tested and inspected before walls close |
| Drinking water | Coating must comply with NSF/ANSI/CAN 61 | Pipe and fittings must comply with NSF/ANSI/CAN 61 |
| Usually fits | Sound pipe in slabs, concrete or hard-to-open finishes | Pipe failing as a material, or a building being upgraded |

## Cost and disruption

Lining prices depend on the system, the product and the access, and there is no reliable local range for it, so this guide does not quote one. A repipe in the San Francisco area typically runs $8,500 to $16,000 for one bath, $12,000 to $22,000 for two and $14,500 to $28,000 for three in PEX, with copper usually higher; the [repipe cost guide](https://hilltoprepipesanfrancisco.com/guide/repiping-cost/) explains what moves the number. When comparing a lining bid with a repipe bid, check that both include the valves, the permit, any service-line work and the patching, because the scopes differ more than the totals suggest.

Lining usually opens fewer walls, but it needs the whole system drained and dry while the coating goes on and cures. A repipe runs new lines while the old ones still serve, so the water is off in stages. The [guide to how invasive repiping is](https://hilltoprepipesanfrancisco.com/guide/how-invasive-is-repiping/) shows where repipe openings tend to land.

## Making the choice

Lining makes the most sense when the pipe walls are sound, access is the main obstacle and the layout works. Replacement makes more sense when the material is failing, flow is restricted, the threads are thin or the building needs the shutoffs and devices the code now requires. The [repipe vs repair guide](https://hilltoprepipesanfrancisco.com/guide/repipe-vs-repair/) covers the wider decision. For a written scope that shows what replacing the pipe in your building would involve, call or send the form.

## Questions about this guide

### Is epoxy pipe lining safe for drinking water?

Only if the specific coating is certified for it. The California Plumbing Code requires materials in contact with drinking water to comply with NSF/ANSI/CAN 61, and a lining becomes the surface the water touches. Ask for the product name and its certification, and how the installer confirms the coating cured fully before the water goes back on.

### Can epoxy lining fix galvanized pipe that has rusted shut?

Not reliably. Lining starts by blasting the rust out, which removes metal along with it. Galvanized is thinnest at its threads, where it usually fails, and a coating does not add strength back. Pipe that is badly narrowed, split or thin at the threads is a candidate for replacement, not lining.

### Does epoxy lining stop pinhole leaks in copper?

It can seal small pinholes, because the coating bridges them from the inside. It does not remove whatever caused the pitting, and it cannot be seen or inspected once the walls are closed. If pinholes are spreading across several runs, the cause and the remaining wall thickness decide whether lining makes sense.

## Related service

### 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

## More guides

- 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 [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.
- Learn [How does repiping a house work?](https://hilltoprepipesanfrancisco.com/guide/repiping-guide/)The whole picture in one place: what the water supply system is, what San Francisco buildings were piped with and why it fails here, how a repipe is scoped, permitted, installed, tested and lived through, and what to ask before agreeing to one.
- Learn [Are galvanized pipes safe for drinking water?](https://hilltoprepipesanfrancisco.com/guide/are-galvanized-pipes-safe/)Galvanized steel is not lead pipe, and San Francisco's tap results are low. The real questions are what the pipe was once connected to, what its rust carries into the water and how much life the steel has left.