Cast iron drain pipe

Entry in Metal pipe · Updated October 29, 2026 · Written by the Know Your Pipes editors from the sources listed under References

Cast iron drain pipe, also called cast iron soil pipe, is gray iron pipe used for drain, waste, vent and sewer lines, and in the United States it is made in two types: hub and spigot, and hubless (no-hub)^[1]. It is joined with rubber gaskets, hubless couplings, or the older lead-and-oakum joint^[1].

Cast iron pipe was first used in the United States at the start of the nineteenth century, imported from England and Scotland for city water and gas-lighting systems^[1].

1 Types and standards

Hub-and-spigot pipe has a bell (hub) on one end that receives the plain spigot end of the next piece^[1]. It is made to ASTM A74 in two wall classes, Service (SV) and Extra Heavy (XH); because the extra wall is added to the outside, the two classes have different outside diameters and need adaptors to connect^[1].

Hubless pipe has plain ends on both pieces and is made to ASTM A888 or CISPI 301 in a single wall class^[1]. CISPI 301 is the institute's own specification for hubless soil pipe and fittings for sanitary and storm drain, waste and vent piping^[2]. The Cast Iron Soil Pipe Institute holds a trademark on the term "CI no-hub," and the trade uses hubless and no-hub to mean the same pipe^[1].

Table source: CISPI handbook and guide specification^[1].

2 Joints

The lead-and-oakum joint packs oakum fiber into the hub and seals it with molten lead, which fills a groove in the hub and is then caulked tight once it cools^[1]. The compression joint replaces that with a one-piece rubber gasket in the hub; CISPI states it can deflect up to 5 degrees without leaking^[1].

Hubless joints use a coupling that slides over the two plain ends: typically a one-piece neoprene gasket inside a stainless steel shield, tightened with stainless steel clamps^[1]. Couplings are made to CISPI 310 and their gaskets to ASTM C564^[1]. The no-hub couplings entry covers coupling types, and transition fittings covers joints to plastic or copper DWV pipe.

3 Corrosion, wear and noise

Gray iron contains about 3 to 4 percent free graphite by weight, and as it corrodes it leaves a dense graphitic layer that slows further attack^[1]. CISPI notes that internal corrosion can come from strong acids or other aggressive wastes with a pH of 4.3 or lower left in contact with the pipe, and that a loose polyethylene wrap is the usual protection in corrosive soils^[1].

CISPI's maintenance guidance applies to every drain material: the system should be maintained on a schedule, with checks for proper slope, adequate support of pipe and components, and clear vents^[3]. Older drain lines that leak or have failed are commonly replaced, sometimes with PVC DWV pipe or ABS pipe where the local code allows. Orangeburg pipe is a separate, fiber-based pipe material with its own entry. Replacement drain and sewer work is done by a licensed plumber under a permit.

Cast iron's density, together with neoprene gasket joints, damps drainage noise, which CISPI cites as a reason it is chosen for multi-family buildings^[1]. Pipe and fittings are sold by size and type through plumbing suppliers; PlumbingSupplyAndMore's soil pipe category (PlumbingSupplyAndMore has the same owners as this reference) is one example.