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Ductile Iron Pipe and Fittings

Ductile iron pipe is the common heavy water main pipe, made to AWWA C151 with joints and linings chosen for the job. This sheet covers how ductile iron is designated, the main joint types, fittings and linings, and what to confirm before ordering.

Ref PV-0011AWWA C151AWWA C110AWWA C153AWWA C111

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Ductile iron pipe is centrifugally cast iron with a nodular graphite structure that makes it strong and tough. It is used for water mains, fire lines, sewer force mains and some industrial lines. Pipe is made to AWWA C151 and designed by AWWA C150. It is sold by nominal size and pressure class. Fittings are either full-body (AWWA C110) or compact (AWWA C153). Joint gaskets and mechanical joint parts follow AWWA C111. Ductile iron pipe has its own outside diameters, known as DIPS, which differ from steel pipe of the same nominal size.

How to identify

Pipe is marked with the maker, size, pressure class, lining and production data. Fittings are cast with the size, angle, joint type and standard. A push-on bell is smooth inside with a gasket groove. A mechanical joint bell has a flange-like rim with bolt holes for a gland. Flanged pipe has flanges threaded or welded on at the plant.

Joints, fittings and linings

Item	What it is	Typical use	Notes
Push-on joint	Spigot pushes into a gasketed bell	Most buried pipe	Fastest to install; not restrained by itself
Mechanical joint (MJ)	Gasket compressed by a bolted gland	Fittings, valves, connections	Uses T-bolts and a gland per AWWA C111
Restrained joint	Locking segments, rings or gripping glands	Bends, dead ends, steep slopes	Restraint length is an engineering design value
Flanged	Flanges on pipe and fittings	Above-ground, vaults, plants	Not for direct burial in most specs
Full-body fitting	Standard laying-length fitting	Traditional fitting choice	AWWA C110
Compact fitting	Shorter, lighter fitting	Common modern choice	AWWA C153
Cement-mortar lining	Interior lining	Potable water	Lining standard is AWWA C104
Polyethylene encasement	Loose PE wrap around pipe	Corrosive soils	Installed per AWWA C105

Key points

Confirm the pressure class on the drawings. Do not substitute a lighter class.
DIPS and IPS outside diameters differ. Use transition couplings or the right fittings when joining PVC, HDPE or steel.
Gasket material must suit the service. Standard gaskets are for water; ask about fuels or chemicals.
Restraint is set by the engineer from thrust calculations. The counter supplies the parts on the plan.
Check that MJ accessory kits (gland, gasket, bolts) match the fitting size.

Common mistakes

Shipping push-on pipe where the plan calls for restrained joints.
Mixing DIPS and IPS couplings.
Forgetting MJ accessory kits on fittings.
Leaving out polyethylene encasement when the spec requires it.

Governing standards: AWWA C151 (ductile iron pipe); AWWA C150 (thickness design); AWWA C110 and C153 (fittings); AWWA C111 (gaskets and mechanical joints); AWWA C104 (cement-mortar lining); AWWA C105 (polyethylene encasement).

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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