By Double J Liner Repair · Pipe Lining · Published 2026-10-23
Cast iron was the standard material for drain and sewer pipes in homes for much of the twentieth century. A lot of San Antonio houses built before the 1980s still have cast iron under the slab and running out to the yard.
Cast iron is strong, but it is not immune to time. After decades of carrying wastewater, many of these pipes are corroding from the inside out.
Wastewater and sewer gases slowly corrode the interior surface of iron pipe. As it corrodes, rough scale builds up on the walls, a process sometimes called tuberculation. That scale narrows the pipe and catches debris, leading to slow drains and recurring clogs.
Over time the bottom of the pipe, where water constantly flows, can thin out and crack along its length. These channel cracks are a common failure point in older cast iron.
Most San Antonio homes sit on concrete slab foundations. Replacing cast iron under a slab traditionally means jackhammering through floors or tunneling underneath the house. That can mean moving out, tearing up flooring and cabinets, and a long restoration process afterward.
The first step is descaling. Specialized tools clean the interior back to a sound surface so the liner can bond properly. Then a UV-cured liner is installed and cured, creating a smooth, new pipe inside the old iron.
The smooth interior of the liner often improves flow compared to the rough, scaled cast iron it replaces. The liner is resistant to corrosion, so the process that destroyed the original pipe no longer applies.
If the pipe still holds its shape, even with cracks and corrosion, lining is usually possible. Sections that have lost large pieces of their wall may need a spot repair first. A camera inspection after cleaning is the only reliable way to know.
It varies widely with water chemistry, usage, and installation, but many cast iron systems in homes built before the 1980s are now showing significant corrosion.
In many cases, yes. Lining works through existing access points, which avoids breaking up the slab.
The liner adds a thin wall, but because it is far smoother than corroded cast iron, flow often improves.
Double J Liner Repair offers sewer camera inspections and free estimates on no-dig sewer repair in San Antonio, backed by a 10-year warranty. Learn more about sewer repair or read more sewer and pipe repair guides.
Double J Liner Repair · 1800 NE Interstate 410 Loop #216, San Antonio, TX 78217 · Phone: (210) 802-2018 · Email: Info@doublejlinerrepair.com
Hours: Monday–Friday 8:00 AM–6:00 PM, Saturday 9:00 AM–2:00 PM, Sunday closed.