7.11 Thermal insulation of mechanical systems

This section contains requirements for the insulation of mechanical systems, including insulation of plumbing systems and equipment, roof storm drain system, hot water piping systems and equipment, chilled water piping and equipment, and the insulation of the duct systems.

• Air-conditioning return ducts located in ceiling spaces used as return air plenums do not require insulation.

• Hot water and chilled water circulating pumps should not be insulated.

• Provide reusable insulation covers at —All check valves

—Control valves

—Strainers

—Filters

—Any other piping component requiring access for routine maintenance

• Insulation exposed to the weather or possible physical damage should be cov­ ered by appropriate metal jackets. All piping with metal jackets should be identi­ fied on the drawings.

The use of insulation must also be evaluated regarding the potential for leakage from piping and/or condensation, which renders insulation a potential site of biological amplification.

7.12 Plumbing system

The plumbing system consists of the water supply distribution system; fixtures and fixture traps; soil, waste, and vent piping; storm water drainage; and acid and industrial waste disposal systems. It extends from connections within the structure to a point 5 ft (1.5 m) outside the structure. The design of all plumbing must comply with the most cur­rent National Standard Plumbing Code, unless otherwise stated.

• Pipe materials for the domestic water system should be specified as nonferrous.

• Underground water pipes must be installed below the recognized frost line or insulated to prevent freezing.

—Service lines enter the building in an accessible location, and when entering through the floor, a displacement type water entrance should be provided.

—When the incoming pressure of water supply exceeds the water pressure nec­essary for proper building operation by 10 psig (68.9 kPa), a pressure-reducing valve must be provided.

7.12.1 Piping Run

Piping runs should be designed to minimize interference with ordinary movement of personnel and equipment.

• The water supply piping is distributed throughout the building, with water mains generally running near the ceiling of the lowest floor.

Neither water nor drainage piping should be located over electrical wiring or equip­ment unless adequate protection against water intrusion (including condensation) damage has been provided. Insulation alone is not adequate protection against condensation.

• Water and waste piping should not be located in exterior walls, attics, or other spaces wherever a danger of freezing exists. Where piping is to be concealed in wall spaces or pipe chases, such spaces should be checked to insure that clear­ ances are adequate to properly accommodate the piping. Water piping should be designed for a maximum flow velocity of 8 ft/s.

Pipe chases and collocation of piping must be evaluated for accessibility and the poten­tial for hosting contaminant repositories if leakage occurs. Both biological and chemical risk should be evaluated, particularly for spaces where small leaks may go unnoticed.

• Cross connections between water supply piping and waste, drain, vent, or sewer piping are prohibited.

—Piping should be designed so that a negative pressure in the water supply pipe and/or a stopped-up waste, drain, vent, or sewer pipe will not cause backflow of wastewater into the water supply piping.

—Single check valves are not considered adequate protection against wastewater backflow.

7.12.1.1 Back-Siphonage

The supply outlet connection to each fixture or appliance that is subject to back-siphonage of nonpotable liquids, solids, or gases must be protected in accordance with the National Standard Plumbing Code.

Depending on the severity of the backflow situation, an air gap, atmospheric vacuum breaker, double check valve assembly, or reduced-pressure device may be required. Severe backflow situations may include systems connected to boilers or converters containing gly-col mixtures, which should require a reduced-pressure device.

• Air gaps will conform to the National Standard Plumbing Code.

• Double-check valve assemblies, reduced-pressure assemblies, atmospheric (non- pressure) type vacuum breakers, and pressure type vacuum breakers will be tested, approved, and listed by the Foundation for Cross-Connection Control and Hydraulic Research.

• Atmospheric type vacuum breakers, hose connection vacuum breakers, and back- flow preventers with intermediate atmospheric vents will be in accordance with American Society of Sanitary Engineering (ASSE) Standards 1001,1011, and 1012.

• Servicing stop valves should be installed in all water connections to all installed equipment items, as necessary for normal maintenance or replacement, and should be shown on the drawings, except when called for in project specifications.

• Water conservation fixtures (low-flow type) conforming to the guide specifica­ tions will be used for all toilets, urinals, lavatory faucets, and shower heads, except where the sewer system will not adequately dispose of the waste material on the reduced amount of water.

• Commercially available water hammer arresters should be provided at all quick closing valves, such as solenoid valves, and will be installed according to manu­ facturers' recommendations. Vertical capped pipe columns are not permitted.

• Electric, refrigerated water coolers should be used for all drinking water require­ ments, except in hazardous areas per NEC Article 500. Refrigerant R-12 should be not be used if possible; use Refrigerant R-22 or R-134a instead.

• Freeze-proof wall hydrants with vacuum breaker backflow preventers should be located on outside walls so that, with no more than 100 ft (30.5 m) of garden hose, an area can be watered without crossing the main building entrances.

• Emergency showers and eyewash stations should be provided where hazardous materials are stored or used or as required by the installation facility manager and should be installed in accordance with ANSI Standard Z385.1, the current version. —Where the eyes or body of any person may be exposed to injurious corrosive

materials, an emergency shower and eyewash station should be provided con­forming to the ANSI Standard Z385.1.

—In accordance with ANSI Standard Z385.1, a heated water system should pro­vide tempered water (60-100°F [16-38°C]) for a 15-min duration at the flow rate required by the installed shower/eyewash.

• The domestic hot-water heating energy source should be steam, HTHW, natural gas, fuel-oil, or electricity. The use of electricity should be avoided if possible. Electricity is permitted for point-of-use water heaters only. Domestic hot-water design temperatures should be 120°F (49°C).

• Criteria determining the need for circulating pumps as shown in the American Society of Heating, Refrigerating, and Air-Conditioning (ASHRAE) Handbook HVAC Applications must be followed. Within buildings operated on a nominal 40-h week or on a nominal two-shift basis (either a 5-day or a 7-day week), a design should include installation of a clock or other automatic control on the domestic hot-water circulating pumps to permit operation only during periods of occupancy, plus 30 min before and after working hours.

• Floor drains should be provided in toilet rooms with three or more toilets. Provide floor drains in shower drying areas serving two or more showers. Provide enough floor drains in utility and boiler rooms to avoid running equip­ ment drain pipes above the floor.

• The selection of pipe and fitting materials for acid waste and vent applications will be based on the type, concentration, and temperature of acid waste to be handled. Acid neutralization tanks should be provided for all acid waste drainage systems.

All acid waste systems must be evaluated for potential worker exposure in case over­head leaks occur. Collocation of caustic and thermal hazard lines must also be evaluated for increased hazard.

• Where feasible, provide circuit vents in a concealed space to a main vent through the roof in lieu of an excessive number of individual roof vents. Waste and vent piping should be concealed unless otherwise specifically instructed.

• Storm drainage will include roof drains, leaders, and conductors within the building and to a point 5 ft (1.5 m) outside the building. Roof drainage systems will be designed in accordance with rainfall intensity-frequency data in the National Standard Plumbing Code.