What should I look for when buying drain pipe materials: pvc vs abs vs cast iron?

PVC is the standard choice for new residential DWV work in most areas. If noise matters (drains running through bedroom walls), consider cast iron for those specific runs. Never mix PVC and ABS with solvent cement. Use a mechanical transition coupling.

What are common mistakes when buying drain pipe materials: pvc vs abs vs cast iron?

Gluing PVC to ABS. The cements are chemically different and the joint will fail. Using PVC for drain runs through areas where noise matters without considering alternatives. Not using primer on PVC joints where code requires it. The joint may fail.

Drain Pipe Materials: PVC vs ABS vs Cast Iron

Overview

Drain pipes carry wastewater by gravity -- no pressure. The three materials used in residential DWV (drain, waste, vent) systems are PVC, ABS, and cast iron. PVC is the current standard. ABS is common in western states. Cast iron is found in older homes and is quieter but heavy and eventually corrodes.

What to Know

PVC (White)

The most common residential DWV material. Schedule 40 is standard. Lightweight, corrosion-proof, easy to cut and join with solvent cement. Requires purple primer before cement in most jurisdictions. Quiet sound dampening is poor -- water flowing through PVC is audible through walls.

ABS (Black)

Similar to PVC but single-step cement (no primer needed). Common in western US and Canada. Cannot be mixed with PVC without a transition fitting. Slightly more brittle than PVC in cold temperatures. Performance and lifespan are comparable to PVC.

Cast Iron

The original DWV material. Extremely quiet -- water noise is absorbed by the dense metal. Very heavy. Joins with no-hub couplings and band clamps. Corrodes from inside over 50-80 years, eventually developing holes and blockages. Found in pre-1980 homes. Replacement with PVC is common during renovations.

Comparison

PVC: $, lightest, most common, solvent cement + primer, some water noise

ABS: $, similar to PVC, single-step cement, common in western US

Cast iron: $$$, heaviest, quietest, corrodes over time, found in older homes

Buying Tips

PVC is the standard choice for new residential DWV work in most areas.
If noise matters (drains running through bedroom walls), consider cast iron for those specific runs.
Never mix PVC and ABS with solvent cement. Use a mechanical transition coupling.
Schedule 40 is standard. Schedule 20 (thin-wall) is for non-structural drain applications only.

Common Mistakes

Gluing PVC to ABS. The cements are chemically different and the joint will fail.
Using PVC for drain runs through areas where noise matters without considering alternatives.
Not using primer on PVC joints where code requires it. The joint may fail.
Ignoring corroded cast iron during a renovation. Replace it now while walls are open.

Bottom Line

PVC for new work. Replace cast iron when walls are open during renovations. ABS is equivalent to PVC where code allows. Use cast iron selectively for noise-sensitive runs.