8.4 Main & Service Installation, Tapping, Repair and Utility Locating (Alabama 811)

8.4 Main & Service Installation, Tapping, Repair and Utility Locating (Alabama 811)

The WPI Water Distribution Class I exam (Alabama Water Grade I) assigns 30 of its 100 questions to equipment installation, operation, maintenance and repair, including "install water lines (service lines, water mains)," "inspect new construction," "disinfect components used during install/repairs" and "perform underground locating, marking and notification." This section ties those tasks to Alabama's rules.

ADEM Construction Requirements (Rule 335-7-7-.03)

• Pipe and materials must not contaminate the water, and gaskets, O-rings and other joining products must be certified to NSF/ANSI Standard 61 and must not support microbial growth.
• Water-sewer separation for mains installed after January 1, 2013 (unless ADEM approves otherwise):
  • At least 5 feet horizontal separation between water mains and sanitary sewer mains.
  • Where mains must cross, a continuous casing around one main so there is at least 5 feet of separation between each end of the cased main and the uncased main.
  • Where possible, the top of the sewer at least 18 inches below the bottom of the water main.
  • No water main may touch a sewer manhole, septic field lines or soil saturated with organic solvents or gasoline unless it is adequately cased.
• Permitted mains must be pressure tested and disinfected, and copies of the pressure test and bacteriological results showing absence of coliform go to ADEM with the request for final inspection before meters are set.

Laying Pipe and Restraining Thrust

• Excavate to grade, provide proper bedding and haunch support, and keep the pipe interior clean. Cap or plug open ends at the end of each day to keep out trench water, soil and animals.
• Install tracer wire and warning tape over plastic pipe so it can be located later.
• Thrust develops at bends, tees, reducers, valves and dead ends. For a dead end or closed valve, thrust equals pressure times pipe area; at a bend it equals $2PA\sin(\theta/2)$ (Section 8.1).
• Thrust blocks must bear on the fitting (not on joints or bolts) and against undisturbed soil, sized for the soil's bearing capacity. Concrete needs time to cure before pressure testing. Restrained joints (wedge-action glands or restrained gaskets) use the friction of a restrained length of pipe instead of concrete.

Pressure and Leakage Testing

AWWA C600 (ductile iron) describes a hydrostatic test at about 1.5 times the working pressure for at least 2 hours. Makeup water needed to hold pressure is compared with the allowable amount:

$$L = \frac{S \times D \times \sqrt{P}}{148{,}000}$$

where $L$ is allowable makeup water in gallons per hour, $S$ is the length of pipe tested in feet, $D$ is the nominal diameter in inches and $P$ is the average test pressure in psi.

Example. 1,000 feet of 8-inch ductile iron main tested at 150 psi:

$$L = \frac{1{,}000 \times 8 \times \sqrt{150}}{148{,}000} = \frac{1{,}000 \times 8 \times 12.25}{148{,}000} = 0.66\text{ gal/hr}$$

Over a 2-hour test, about 1.3 gallons of makeup water is allowed. More than that means a leaking joint, valve or fitting that must be found and fixed before retesting.

Service Connections

A typical service runs from the main to the customer's meter:

1. Corporation stop threaded into the main (directly, or through a service saddle).
2. Service line of copper (Type K) or polyethylene, often with a gooseneck loop to absorb movement.
3. Curb stop with a curb box, the utility's shutoff near the property line.
4. Meter setter and meter in a meter box, then the customer's line.

Tapping practice:

• Use a service saddle on PVC and wherever the main's wall is too thin for adequate thread engagement; direct taps are limited to pipe materials and sizes that allow enough threads.
• A tapping machine cuts the hole under pressure through the corporation stop, so the main stays in service.
• For a new branch main, a tapping sleeve and tapping valve are installed and pressure tested before the cut. The cut-out disc (coupon) is retrieved and saved as a record of main condition.
• ADEM Rule 335-7-9-.03 requires a backflow prevention device on each new service connection (Section 1.5).

Repairing Main Breaks

1. Locate and isolate: close valves to isolate the smallest possible section; exercise and record valves as you go. Notify affected customers, the fire department for hydrants out of service, and critical users such as hospitals.
2. Request an emergency locate through Alabama 811 before digging, and protect the excavation (Section 12.2).
3. Keep positive pressure if possible. Contamination risk depends on whether the main lost pressure or was dewatered. If pressure stayed positive, flush and return to service. If the main was depressurized or dewatered, treat it as a contamination risk: flush, disinfect and collect bacteriological samples as AWWA C651 describes, and follow ADEM's direction on any boil-water advisory.
4. Repair: full-circle stainless repair clamps for holes and circumferential cracks; cut-in sleeves or pipe replacement for longitudinal splits.
5. Disinfect repair parts: swab or spray fittings, clamps and pipe interiors with a strong hypochlorite solution (about 1 percent is common practice) before installation.
6. Document location, cause, pipe material, condition, valves used and customers affected in the maintenance record and GIS.

Inspecting New Construction

Inspectors check depth of cover, bedding, separation from sewers, thrust restraint, valve boxes centered and plumb, hydrant drains and gravel, tracer wire continuity, the pressure and leakage test, disinfection and bacteriological results, and complete as-built records.

Locating and Marking: Alabama's Underground Damage Prevention Law

Alabama's law is Code of Alabama 1975, Title 37, Chapter 15, and Alabama 811 is the one-call center.

• Excavators must notify Alabama 811 at least 2 but not more than 10 working days before excavating, not counting the day of notification. Demolition and blasting have their own notice windows.
• A locate notice is valid for 20 working days from the start date and must be renewed at least 2 working days before it expires if work continues.
• Excavators should white-line the proposed dig area, confirm operator responses before digging, and hand dig or pothole within the tolerance zone of at least 18 inches on each side of a marked facility (plus the facility's width). Damage to any facility must be reported immediately.

APWA uniform color code for marks:

When your utility receives tickets, its locators mark water lines in blue using maps, tracer wire and electronic locators, and respond within the time the law allows.