6.3 Pipe Materials, Main Installation, Service Connections & Meters

6.3 Pipe Materials, Main Installation, Service Connections & Meters

1. Approved pipe materials

15A NCAC 18C .0406(a) states that water pipes shall be cast iron, ductile iron, reinforced concrete, plastic, or other material designed for potable water system service, and shall meet AWWA standards or be certified as meeting ANSI/NSF Standard 61, Drinking Water System Components – Health Effects. The pressure rating class of the pipe must exceed the maximum design pressure in that section of the system, and the quality of pipe must be stated in the project specifications.

2. Installing a main

1. Bedding and cover. Provide uniform support on bedding material; backfill without dropping rock onto the pipe. Cover must be below the frost line or at least 30 inches, whichever is greater (18C .0904(a)), and 12 inches minimum clearance is maintained between the water main and other utilities (.0904(b)).
2. Separation from sewers (18C .0906). Water mains are laid at least 10 feet laterally from existing or proposed sewers. Where local conditions prevent that, the water main goes in a separate trench with the bottom of the water main at least 18 inches above the top of the sewer, or on an undisturbed earth bench in the same trench at that same elevation difference. At crossings, maintain a minimum 18-inch vertical separation, preferably with the water main above.
3. Thrust restraint. Pressure acting on a change in direction creates an unbalanced force. Bends, tees, caps, plugs, hydrants, and valves are restrained by thrust blocks poured against undisturbed soil or by restrained joints. Never pour a thrust block against backfill, and never bury an unrestrained cap under pressure.
4. Pressure and leakage testing (18C .0905). New mains are tested for leakage and repaired and retested as specified in AWWA standards — normally a hydrostatic test at a specified pressure with allowable makeup water computed from length, diameter, and pressure.
5. Disinfection (18C .1001, AWWA C651). Interior surfaces are disinfected with hypochlorite or chlorine solutions, then bacteriological samples are taken; the main may not be placed in service until laboratory results are satisfactory. Highly chlorinated water must be neutralized before discharge.
6. Records. Record the material, class, diameter, valve locations, fitting types, and any restraint used, and update the system map — an accurate map is what makes the next main break a 30-minute event instead of a 4-hour event.

3. Service connections

A typical service runs: corporation stop at the main (installed by direct tap or tapping saddle, often wet-tapped under pressure), service line, curb stop with curb box at the property line, meter setter and meter, and the customer's plumbing beyond.

• Materials: copper, polyethylene, and PVC dominate today. Lead goosenecks and lead-soldered joints persist in older systems and are exactly what the service line inventory targets.
• Lead-free requirement (18C .0408). Pipe, solder, and flux used in a public water system must meet the lead-free requirements; lead solder in potable plumbing has been prohibited since 1986.
• Service line inventory. Under the LCRR, every service line must be categorized as lead, galvanized requiring replacement, non-lead, or lead status unknown, on both the utility-owned and customer-owned portions, and the inventory must be publicly accessible.
• Never a partial replacement. Cutting a lead line and leaving part of it in place disturbs the scale and can release particulate lead; the LCRI requires full replacement of lead and galvanized-requiring-replacement lines.

4. Meters

Accuracy and testing. New meters are expected to register within about 98.5 to 101.5 percent across their normal test range, with wider tolerance at minimum flow. Meters lose accuracy in one direction — they under-register as they wear — so an aging meter population quietly becomes apparent water loss and lost revenue. A meter testing and change-out program sized by meter age and volume passed is standard practice; large meters are tested most often because they carry the most revenue.

Installation practice: install in the direction of the arrow, provide straight pipe upstream where the manufacturer requires it, protect against freezing, and keep a backflow preventer appropriate to the hazard on any service where the customer's use warrants it.

[!WARNING] Every tap is a potential cross-connection. A service that feeds an irrigation system, a boiler, a chemical injector, or an auxiliary well is a hazard that must be evaluated and protected under 18C .0406(b). The time to identify it is at the new service review — which is exactly why 18C .0406(b)(6)(D) requires systems with five or more testable assemblies to review new connections and account changes.