4.1 Water Piping Materials, Joints, Lead Limits, Under-Slab Rules, & Velocity (UPC 604, 605, 609, 610.12)
Key Takeaways
Wetted surfaces of pipes, fittings, and fixtures carrying drinking water may contain no more than a 0.25 percent weighted average of lead; solder and flux no more than 0.2 percent (UPC 604.2).
Copper water tube must weigh at least Type L; Type M is permitted aboveground in or on a building or underground outside of structures (UPC 604.3).
Under a slab within a building, copper tube is installed without joints where possible, and any joints are brazed with wrought copper fittings (UPC 609.3).
Velocities in copper and copper-alloy tube systems may not exceed 8 feet per second cold and 5 feet per second hot (UPC 610.12.1).
PEX, PEX-AL-PEX, PE-AL-PE, and PE-RT may not be installed within the first 18 inches of piping connected to a water heater (UPC 604.13).
Materials Standards (UPC 604)
- 604.1: Pipe, tube, fittings, solvent cements, thread sealants, solder, and flux used in systems supplying drinking water must meet NSF 61. Copper-alloy fittings with more than 15% zinc used in plastic piping systems must resist dezincification (NSF 14). Materials in one system should be alike unless the AHJ approves otherwise.
- 604.2 Lead: Wetted surfaces of pipe, fittings, fixture fittings, and fixtures carrying drinking water may contain no more than a 0.25% weighted average of lead. Solder and flux may contain no more than 0.2% lead. Non-drinking-water applications may use up to 8% (604.2.1).
- 604.8: Piping previously used for anything other than potable water may not be reused.
- 604.6 and 604.7: Cast-iron fittings up to and including 2 inches, and malleable iron fittings, used with potable water piping must be galvanized.
Copper Tube Types (UPC 604.3 and 604.4)
| Type | Stripe on hard-drawn tube | Where the UPC allows it for water |
|---|---|---|
| K | Green | Anywhere, including under slabs and underground |
| L | Blue | The UPC minimum weight for water piping; anywhere |
| M | Red | Only aboveground in or on a building, or underground outside of structures |
| DWV | Yellow | Drainage and vent only; not water supply |
Exam trap: Type M is not banned from all underground work. The UPC allows it underground outside structures. It may not be used under a slab within the building foundation, where the rules of 609.3 apply.
Joining Methods (UPC 605)
| Joint | Key requirements |
|---|---|
| Soldered (605.1.4) | ASTM B828 sequence; cut square, ream, clean bright; ASTM B813 flux; solder meeting 604.2 |
| Brazed (605.1.1) | Filler with a liquidus above 1,000°F; joint surfaces cleaned bright |
| Flared (605.1.2) | Soft copper only; cut square, ream, and flare with a proper tool |
| Pressed (605.1.3.2) | Elastomeric O-ring; tube fully inserted and marked at the fitting shoulder; pressed with the manufacturer's tool |
| Push fit (605.1.3.3) | ASSE 1061; cut square, chamfer, ream, insert fully, and check against the insertion mark |
| Threaded copper-alloy (605.1.5) | ASME B1.20.1 threads; sealant on male threads only |
| CPVC solvent cement (605.2.2) | Orange ASTM F493 cement with ASTM F656 primer; listed one-step yellow or red cement allowed for ASTM D2846 pipe 1/2 through 2 inches |
| PVC solvent cement (605.12.2) | Purple ASTM F656 primer, ASTM D2564 cement; hold the joint 1 minute |
| Threaded plastic (605.2.3, 605.12.3) | Only Schedule 80 or heavier may be threaded, and the pressure rating drops 50% |
| Mechanically formed tees (605.1.3.1) | Collar height at least 3 times the branch wall thickness; brazed |
| Slip joints (605.14) | Water piping: only on the exposed fixture supply |
PEX joints follow the manufacturer's instructions with fittings marked on the tubing (605.9). PE heat-fusion joints use butt, socket, or electrofusion (605.6.1).
Connectors (UPC 604.5, 604.12, 604.13)
- Flexible water connectors must be readily accessible. Those under continuous pressure must meet ASME A112.18.6/CSA B125.6.
- Flexible corrugated copper, copper-alloy, or stainless connectors are limited to 30 inches for fixtures, 72 inches for washing machines, and 120 inches for dishwashers and ice makers.
- Metallic water heater connectors may not exceed 24 inches. PEX, PEX-AL-PEX, PE-AL-PE, and PE-RT may not be installed within the first 18 inches of piping connected to a water heater.
Underground and Under-Slab Water Piping (UPC 609.1–609.3)
- 609.1: Building supply yard piping must be at least 12 inches below the average local frost depth, with at least 12 inches of cover below finish grade. Copper tube may be bent only with equipment that does not deform or reduce its cross-section.
- 609.2 Common trench: Water pipe may share a trench with a clay sewer, or a sewer of material not approved inside buildings, only if the bottom of the water pipe is at least 12 inches above the top of the sewer and the water pipe sits on a solid shelf at least 12 inches horizontally from the sewer. Water pipe crossing such a sewer must be at least 12 inches above it.
- 609.3 Under a slab within a building: Ferrous pipe needs a machine-applied protective coating; galvanizing alone is not adequate. Copper tube is installed without joints where possible. Where joints are allowed, they must be brazed, with wrought copper fittings. "Within a building" means within the fixed limits of the foundation.
Velocity Limits (UPC 610.12)
Section 610.1 requires water systems to be designed so the code's maximum velocities are not exceeded:
| System | Maximum velocity |
|---|---|
| Copper and copper-alloy tube and fittings, cold water (610.12.1) | 8 ft/s |
| Copper and copper-alloy tube and fittings, hot water (610.12.1) | 5 ft/s |
| Copper fittings used in tubing of other materials (610.12.2) | 8 ft/s cold, 5 ft/s hot |
High velocity erodes copper, especially at elbows and tees on the hot side, and it makes noise. Table 610.4 and Appendix A sizing are built to keep velocities within these limits.
A plumber proposes Type M hard copper for water distribution in the walls of a two-story house and for the underground building supply between the meter and the house. Under UPC 604.3, is this allowed?
No, copper water tube must be Type K everywhere
Yes, Type M is permitted aboveground in or on a building and underground outside of structures
Only the underground portion may be Type M
Only if every joint is brazed
What is the maximum lead content allowed in solder and flux used on piping that conveys water for human consumption under UPC 604.2?
8 percent
0.2 percent
0.25 percent
2 percent
A PEX distribution system is being connected to a new storage water heater. What does UPC 604.13 require?
PEX may connect directly to the heater nipples
PEX may not be installed within the first 18 inches of piping connected to the water heater
PEX must be sleeved for the first 6 inches
PEX must be Type K rated
Sections you finish are checked off in the contents.