The chemical smell during sewer lining, and keeping it out of the house
Updated October 30, 2026 · 3-minute read · Old House Sewer Lines
The CIPP styrene smell comes from the resin that hardens a sewer liner, and Purdue University researchers found it can get inside when pressure from the lining work pushes water out of plumbing traps. A dry or blown trap leaves an open path from the sewer to the room.
Cured-in-place pipe, or CIPP, is a fabric tube soaked in resin, put into the old pipe by inversion or by pulling it in, then cured with hot water or steam, the U.S. Environmental Protection Agency says (EPA, 2004). The ASTM standards for the process, F1216 and F1743, also list light curing. Where the resin is styrene-based, styrene is what comes off as it cures. The method itself is explained in CIPP sewer lining.
How fumes get indoors
Every fixture in a house has a trap that holds a water seal. The state plumbing code requires that seal to be 2 to 4 inches deep (§1002.4, ICC). Purdue's CIPP Safety group reported in a peer-reviewed study that external pressure applied by contractors during the process can displace those seals, letting styrene-laden air into buildings (Purdue CIPP Safety). The same researchers recommend treating a waste discharge from the process as a hazardous release, which includes getting people out of the building.
North Dakota State University Extension names basement floor drains and the drains of fixtures that see little use as the traps most likely to dry out, and says pouring a quart of water into such drains every three to four weeks keeps them sealed (NDSU). Refilling every trap before the crew starts, and again after they finish, is a step a homeowner can take. The sewer gas smell item covers other ways odors get in.
Resin type matters
A second Purdue study compared resins. The styrene-based resin held 39 percent volatile organic compounds by weight; the non-styrene resin held 4 percent. Under the same conditions, non-styrene composites released less than 1 percent VOC by weight to air, against 8.8 to 26.4 percent for the styrene composites. Ask a lining contractor which resin it uses, how it handles curing exhaust, and what it does to protect trap seals.
Water and the state's experience
Styrene can also reach water. In a Virginia DOT study of seven steam-cured styrene installations summarized by Caltrans, five sites exceeded EPA's 0.1 mg/L drinking-water limit for styrene, and it was detected up to 88 days after installation (Caltrans, 2012). Virginia suspended styrene CIPP for surface or storm water pipes while it revised its specifications. The same report says the New York State DOT tightened its own rules after styrene concerns on highway culverts. Those cases concern state highway pipes, not house laterals.
Background
Lining is licensed contractor work with a permit, and it is not always possible: a liner simply copies whatever pipe it sits in, so the City of Fairfax, Virginia, rules out lines that are collapsed, pitched backward or fragile until they are fixed. See when sewer lining won't work. Caltrans reports a study finding 5- to 25-year-old liners in excellent condition, with an intended design life of about 50 years; early results are encouraging but not a guarantee. For telling a gas leak from other smells, see gas smell or sewer smell.
Video from Purdue Engineering, an outside channel: Purdue's Andrew Whelton describes a study finding that the white plume from steam-cured pipe liners holds organic chemical vapors. Nothing loads from YouTube until you press play.
Key facts
- Contractor-applied pressure during CIPP can displace plumbing trap seals and let styrene-laden air in (Purdue).
- Styrene resin held 39 wt% VOCs against 4 wt% for a non-styrene resin in a Purdue study (Purdue).
- Fixture traps must hold a 2- to 4-inch water seal (§1002.4, ICC).
- A quart of water every three to four weeks keeps little-used drains sealed (NDSU Extension).
- Five of seven Virginia sites exceeded EPA's 0.1 mg/L styrene limit in water, with detections up to 88 days later (Caltrans).