Interceptors and Special Wastes: Grease, Oil, Sand, and Chemicals
Purpose of interceptors
Interceptors remove grease, oil, sand, lint, or other harmful substances before waste enters the drainage system or the public sewer. Grease interceptors are required for restaurants and other food-handling establishments. Sand and oil interceptors serve garages and car washes. Lint interceptors serve laundry facilities. Acid-neutralizing systems serve laboratories.
Design and installation
Interceptors must be sized for the expected flow and located so they can be serviced. They must have accessible covers, adequate venting, and proper flow control. Grease interceptors must be installed outside the building or in a location that allows maintenance without contaminating food areas. The interceptor must be protected from freezing.
Maintenance
Interceptors require regular cleaning and inspection. Records may be required. An interceptor that is not maintained becomes a blockage and odor source.
Traps in questions
Watch for interceptors that are undersized, inaccessible, or missing. Also watch for questions about which fixtures must connect to an interceptor and which may bypass it.
Worked example
A restaurant with a three-compartment sink, a prep sink, and a dishwasher needs a grease interceptor sized for the combined flow. The interceptor must be accessible for pumping and must be vented. If it is installed under a slab without access, it is noncompliant.
Rule of thumb
Any fixture that discharges fats, oils, grease, sand, or chemicals needs an interceptor sized for flow and accessible for service.
Health, Safety, and Water Quality Requirements
Potable water protection
The highest priority is protecting potable water from contamination. Cross-connections must be controlled by air gaps, vacuum breakers, or backflow preventers. The type of protection depends on the degree of hazard. An air gap provides the highest protection. Backflow preventers must be tested and maintained.
Sanitation and safety
Plumbing systems must prevent the entry of sewer gas, protect against scalding, and provide adequate ventilation. Water heaters must have temperature and pressure relief valves piped to a safe discharge. Fixtures must be cleanable. Materials must not leach harmful substances into potable water.
Traps in questions
Watch for missing relief valve piping, improper backflow protection, and discharge of relief valves to unsafe locations. Also watch for questions about lead-free requirements and water treatment.
Worked example
A water heater relief valve is piped to a floor drain through an air gap. If the pipe is directly connected to the drain, it is noncompliant because backflow could occur. The discharge must terminate safely and visibly.
Rule of thumb
Protect potable water first, protect people from scalding and gas second, and make every safety device testable and visible.
Storm Drainage Systems: Roofs, Leaders, and Site Water
Storm drainage basics
Storm drainage systems collect rainwater from roofs, courts, and paved areas and convey it to a storm sewer or approved disposal point. Roof drains, leaders, and area drains must be sized for the design rainfall intensity. The steeper and larger the pipe, the more it can carry.
Installation rules
Storm drains must be trapped and vented where they connect to a combined sewer, and they must not connect to the sanitary system unless permitted. Leaders must be supported and protected from freezing. Roof drains need strainers and, in cold climates, protection against ice. Overflow provisions may be required for roofs.
Traps in questions
Watch for storm drains connected to sanitary sewers, missing traps, and undersized leaders. Also watch for questions about secondary roof drainage.
Worked example
A flat roof drains through a leader to a storm sewer. If the leader connects to the sanitary building drain, the installation is noncompliant unless the code permits combined discharge. The leader must be sized for the roof area and rainfall intensity.
Rule of thumb
Storm water goes to storm drainage, sanitary waste goes to sanitary drainage, and the two meet only where the code expressly allows it.
Plumbing Facilities for Persons with Disabilities and Barrier-Free Design
Accessibility principles
Accessible plumbing facilities must be usable by people with disabilities. Key concepts include reach ranges, clear floor space, turning space, knee and toe clearance, and operable parts. Fixtures must be mounted at accessible heights and controls must be operable with one hand without tight grasping or twisting.
Fixture-specific requirements
Water closets in accessible compartments need grab bars, proper seat height, and clearance on both sides. Lavatories need knee clearance and insulated pipes. Showers need seats, grab bars, and controls within reach. Drinking fountains need spout height and clearance. Urinals need rim height and clearance.
Traps in questions
Watch for grab bars installed at the wrong height, lavatories without pipe protection, and controls out of reach. Also watch for questions about clear floor space measured from the fixture.
Worked example
An accessible lavatory is installed at 34 inches above the floor with a knee clearance of 27 inches. If the drain pipe is exposed and uninsulated, it must be protected to prevent burns. If the faucet cannot be operated with one hand, it is noncompliant.
Rule of thumb
If a person in a wheelchair cannot approach, reach, and operate the fixture, the installation fails accessibility requirements regardless of pipe sizing.
Inspection, Testing, Maintenance, and Certification
Inspection stages
Inspections occur at defined stages: before covering underground piping, before concealing rough-in, and at final completion. The AHJ must be notified when work is ready for inspection. Concealed work that was not inspected may need to be exposed.
Testing requirements
Drainage and vent systems are typically tested with water or air. A water test fills the system and holds it for a specified time; an air test uses pressure and a gauge. Water supply systems are tested under pressure, usually at a level above normal working pressure, and must hold without loss. Gas piping has its own test requirements.
Maintenance and certification
Backflow preventers, relief valves, and fire sprinkler systems require periodic testing and certification. Records must be kept. Interceptors require cleaning records. Medical gas systems require special certification.
Traps in questions
Watch for tests conducted at the wrong pressure, tests without gauges, and missed inspections before concealment.
Worked example
A new water supply system is tested at 100 psi for one hour with no drop. If the gauge shows a drop, the system must be repaired and retested before approval. The test must be witnessed or documented as required.
Rule of thumb
Test before you cover, document every test, and keep records for every device that requires periodic certification.