Trenchless Water Main Rehabilitation
Upgrading aging infrastructure is essential to ensure reliable water service to our customers. In some cases, water pipes, also known as water mains, do not need to be fully replaced and can instead be rehabilitated using a trenchless method known as Cured-in-Place Pipe (CIPP).
CIPP eliminates the need for major excavation, which is typically required to replace water mains. Instead, this method involves inserting a new interior lining into the existing pipe, which is then hardened or “cured” to form a new pipe within the old one. This process restores the strength of the water main and extends its service life.
There are many benefits to using this trenchless method, including:
- Shorter construction duration compared to open-cut methods
- Reduced disruption to the community, as it avoids extensive excavation, minimizes street repaving, limits temporary parking restrictions, and lessens traffic impacts
- Lower environmental impact, including reduced dust, noise, and construction-related emissions
Frequently Asked Questions
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How does CIPP work?
- Access: Crews will excavate small access pits to reach the existing water main.
- Inspection: Crews conduct a closed-circuit television (CCTV) inspection using a high-definition camera to inspect the pipe conditions.
- Liner Installation: A flexible liner is inserted into the existing pipe through one of the access points.
- Curing: The liner is inflated with hot water to press it against the interior of the existing pipe. The heat cures resin embedded in the lining, forming a rigid, seamless new pipe within the old one.
- Reinstatement & Completion: Once fully cured, pipes are pressure tested and disinfected before being put back into service.
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How long is CIPP good for?
The liners used in CIPP vary, but are generally long-lasting, extending pipe life up to 100 years.
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Will my water be turned off during the CIPP process?
When CIPP is used to rehabilitate water transmission mains, water service interruptions are typically not required. Properties receive water through distribution mains, which operate separately from transmission mains. Currently, all SFPUC water projects utilizing CIPP involve transmission mains only.
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Will CIPP impact my water quality?
No. The process uses a type of material, called a membrane, that is certified for drinking water. It will line the interior of the existing pipeline. All of the construction materials that come into contact with drinking water are certified. The National Sanitation Foundation (NSF) sets standards that prevent the water from being contaminated by anything in the lining.
When the lining is in place, the water main is disinfected. We check to make sure there are no bacteria, organic compounds or taste issues before putting the pipeline into use.
SFPUC tests the water in our system daily. These tests show that the water meets or goes beyond all health standards set by the state or federal government.
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How do you determine whether to use CIPP or open-cut construction?
Typically we use CIPP lining when long segments of pipe can be taken out of service without disrupting customers, and we use open-cut construction in areas with many service connections where a multi-day shutdown and temporary above ground bypass lines would be too disruptive. Lining is a good alternative in locations like freeways, bridges, and parks where there are no customer service connections and open-cut construction would be challenging or too impactful.
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Is CIPP a temporary fix? Why not just install a new steel pipeline?
CIPP is a long‑term rehabilitation method with a life expectancy comparable to new ductile iron or steel pipelines. It creates a durable, structurally independent liner inside the existing pipe, extending its service life for decades. Determining if a segment of pipe will be rehabilitated via CIPP or replaced by installing a brand‑new pipeline requires an evaluation of several factors, including number and location of existing connections, bends, and features like valves.