Why cast iron gets rough inside

Cast iron was a standard drain material when many Fullerton slab-on-grade tract homes were built. Over decades, the inside surface corrodes. Rust and mineral deposits build into bumps and ridges, sometimes called tuberculation, that narrow the pipe and catch whatever passes. Local hard water, a blend of groundwater and imported water, can add to mineral buildup over time.

Under a slab, those pipes are out of sight and hard to reach. Symptoms usually show up as slow drains in bathrooms and the kitchen, repeat clogs, or toilet paper snagging in the same spot a camera can see.

Descaling versus jetting

The terms overlap. Here is how they are usually meant.

Mechanical descaling

  • Uses a spinning chain or abrasive head on a cable
  • Knocks scale off the walls
  • Common for heavy tuberculation
  • Must be controlled to avoid damaging thin pipe

Hydro jetting

  • Uses water pressure and a nozzle
  • Removes softer buildup and flushes debris
  • May be used after descaling to clear loosened material
  • Pressure must suit the pipe condition

Signs the pipe may be too far gone to clean

  • The camera shows a channel worn through the bottom of the pipe.
  • Soil or gravel is visible inside the line.
  • Lengthwise cracks or splits in the pipe wall.
  • Flaking sections that break off under light pressure.
  • Repeated backups even shortly after a thorough cleaning.

How a descaling job usually goes

  1. Camera survey.The line is inspected to judge scale depth and wall condition.
  2. Choose tools.The plumber picks a chain size, cutter or nozzle suited to the pipe diameter and condition.
  3. Clean in passes.Scale is removed gradually, with checks between passes on weaker sections.
  4. Flush.Loosened scale is flushed downstream, often with a jetter.
  5. Re-inspect.A final camera pass shows the result and any defects that were hidden under the scale.

Questions to ask about under-slab cast iron

  1. How thick is the scale, and how much wall is left?
  2. Will you use a chain, a jetter or both?
  3. If the pipe is too weak, what are the options short of breaking up the floor?
  4. Is lining a possibility for this line once it is cleaned?

Common questions

Is descaling a permanent fix?

It restores the pipe's opening, but cast iron continues to corrode. How long the result lasts depends on the remaining wall and how the line is used.

Can descaled cast iron be lined?

Often, cleaning is the first step before lining. Whether a line is a good candidate depends on its condition and layout; ask the plumber after the camera inspection.

Will descaling damage my pipe?

It can if the pipe is very thin or the tool is too aggressive. A camera survey first and a careful choice of tool reduce that risk.

General information for Fullerton, not a quote or professional advice. In an emergency, call 911.