Schedule 40

Schedule 40 refers to the wall thickness classification of PVC pipe as defined by ASTM D1784. At a given nominal diameter, Sch. 40 has thinner walls than Schedule 80 but heavier walls than thin-wall or DWV (drain-waste-vent) PVC. The 100 psi rating applies to cold water; pressure drops significantly at elevated temperatures, so Sch. 40 is not rated for hot water distribution and is prohibited by code in most jurisdictions for that use.

In the field, Sch. 40 is the go-to for water supply lines, irrigation, some pool plumbing, and above-ground applications where the lower cost and easier cutting justify the trade-off in strength. It's lighter and faster to run than Schedule 80, which is why it dominates new construction and repair work in residential settings. Always verify local code before using it—some jurisdictions limit or prohibit it in certain applications, particularly where it runs underground or inside conduit.

Do not confuse Sch. 40 with DWV (drain) PVC, which has even thinner walls and lower pressure ratings. Sch. 40 is pressure-rated; DWV is not. Mixing them in a system creates code violations and reliability problems.