Specifying pipe and piping materials
Plumbing piping is concerned with the flow of many different liquids, solids, and gases. Both potable and non-potable fluids flow within these systems. Due to the wide variety of fluids carried within plumbing systems, the associated piping is categorized as either domestic water or drainage and vent piping.
Domestic water: Soft copper tubing, which complies with ASTM B88 for types K and L, and ASTM B88M for types A and B with wrought copper solder-joint pressure fittings (ASME B16.22).
Hard copper tubing, which complies with ASTM B88 for types L and M, and ASTM B88M for types B and C with cast copper solder-joint fittings (ASME B16.18), wrought copper solder joint fittings (ASME B16.22), bronze flanges (ASME B16.24), and copper unions (MSS SP-123). Pressure-seal fittings are allowed for this tubing as well.
Copper piping types and associated standards have been taken from MasterSpec section 22 11 16. Copper domestic water piping design is limited by the code requirements for maximum flow rates. They are stated in the plumbing codes as follows:
2012 Uniform Plumbing Code section 610.12.1 states: Maximum velocities in copper and copper alloy tube and fitting systems shall not exceed 8 fps in cold water and 5 fps in hot water.These values are also reiterated in “The Copper Tube Handbook,” which uses these values as the recommended maximum velocities for these system types.
Stainless steel piping, which complies with ASTM A403 for type 316 with similar fittings using welded or grooved couplings is used for both larger domestic water piping and direct replacement of copper piping. As copper prices have increased, stainless steel piping has become more common within domestic water piping systems. Piping types and associated standards have been taken from the Veteran’s Administration (VA) MasterSpec Section 22 11 00.
A new development that will be brought into application and compliance in 2014 is the Federal Reduction of Lead in Drinking Water Act. This is a federal implementation of the current California and Vermont laws regarding lead content found within the waterway of any piping, valves, or accessories used within the domestic water system. The law states that all wetted surfaces of pipes, fittings, and fixtures must be “lead-free,” which translates to a maximum lead content of “not more than a weighted average of 0.25% (lead).” This requires that manufacturers produce “lead-free” cast products to meet the new letter of the law. UL outlines the details in “An Overview of Regulations for Lead Levels in Drinking Water System Components.”
Drainage and venting: Hubless cast iron soil pipe and fittings, which complies with ASTM A 888 or Cast Iron Soil Pipe Institute (CISPI) 301. Sovent stack fittings, which comply with ASME B16.45 or ASSE 1043, can be used with a hubless system.
Hub-and-spigot cast iron soil pipe and fittings must comply with ASTM A 74, with rubber gaskets (ASTM C 564), and pure lead and oakum or hemp fiber calking materials (ASTM B29).
Both of these piping construction types are acceptable for building use, but hubless piping and fittings are most commonly used above grade within commercial buildings. Cast iron piping with CISPI hubless piping couplings allows for a permanent installation that can be reconfigured or accessed by disassembling the band clamps, but still retains the metallic piping mass to reduce breakout noise from waste flow through the pipe. The drawback to castiron piping is deterioration of the pipe from acidic waste materials found in typical installations serving bathrooms.
Stainless steel piping and fittings with socket and spigot ends, which complies with ASME A112.3.1 are found in above-grade drainage systems in place of cast iron piping. Stainless steel piping is also used within the first segments of piping connecting to floor sinks where soda products are drained to reduce the damage due to corrosion.
Solid-wall PVC piping, which complies with ASTM D 2665 (drain, waste, and vent), and cellular-core PVC piping, which complies with ASTM F 891 (schedule 40), socket fittings (ASTM D 2665 made to ASTM D 3311, drain, waste, and vent patterns and to fit schedule 40 pipe), adhesive primer (ASTM F 656), and solvent cement (ASTM D 2564). PVC piping can be found above and below grade within commercial buildings, though it is more often specified below grade due to breakout noise from the piping and specific code requirements.
Within the Southern Nevada building jurisdiction, the code amendment to the 2009 International Building Code (IBC)states:
603.1.2.1 Equipment rooms. Combustible piping shall be permitted to be installed in an equipment room that is enclosed by 2-hour fire-resistance rated construction and protected throughout by automatic sprinklers. The combustible piping shall be permitted to be extended from the equipment room to other rooms provided the piping is encased in an approved, dedicated 2-hour fire-resistance rated assembly. Where such combustible piping penetrates a fire-resistance rated wall and/or floor/ceiling assembly, the penetration shall be protected by a through-penetration firestop system that is listed for the specific piping material and that has F and T ratings not less than the required fire resistance rating of the penetrated assembly. The combustible piping shall not penetrate more than a single floor.
This requires that all combustible piping (plastic or otherwise) be encased in 2-hour rated construction when present within a Type 1A building as defined by the IBC. There are some benefits to using PVC piping within a drainage system. PVC is more resistant to corrosion and oxidation caused by waste and soils from bathrooms than cast-iron piping. PVC piping also resists corrosion from the surrounding soils when installed underground (as indicated in the HVAC piping section). PVC piping used within drainage systems has the same limitations found within the HVAC hydronic systems with a maximum service temperature of 140 F. This temperature is further solidified by the Uniform Plumbing Code and International Plumbing Code requirements, which state that any discharge into a waste receptor must be below 140 F.
2012 Uniform Plumbing code section 810.1 states: No steam pipe shall be directly connected to a plumbing or drainage system, nor shall water having a temperature above 140 F (60 C) be discharged under pressure directly into a drainage system.
2012 International Plumbing Code section 803.1 states: Steam pipes shall not connect to any part of a drainage system or plumbing system and water above 140 F (60 C) shall not be discharged into any part of a drainage system.
Specialty piping systems are associated with conveying atypical fluids. These fluids can range from salt water aquarium piping applications to chemical feed piping for pool equipment systems. Aquarium piping systems are not commonly found within commercial buildings, but they are installed in some hospitality properties, with remote piping systems routing from a central pump room to various locations. Stainless steel would appear to be an appropriate piping type for saltwater systems due to its ability to inhibit corrosion with other water systems, but in actuality saltwater will pit and deteriorate stainless steel piping. For this type of application, CPVC plastic or copper-nickel marine-grade piping meets the corrosive requirements; when routing this piping within a large commercial property, the combustibility of the pipe must be taken into account. As indicated above, in Southern Nevada the use of combustible piping requires an alternate means request to show compliance with the intent of the code for the associated building types.
Pool piping conveying treated water for human immersion contains diluted quantities of chemicals (both 12.5% sodium hypochlorite bleach and muriatic acid can be used) to maintain a specific pH level and chemical balanceto meet health department requirements. In addition to the diluted chemical piping, full concentrations of chlorine bleach and other chemicals must be conveyed from bulk storage locations and specific equipment rooms. CPVC piping meets the chemical resistance to convey chlorine bleach, but high-silicon iron piping can be substituted for chemical piping applications when routing through noncombustible building types (example: Type 1A). It is durable, but more brittle than standard cast-iron piping and weighs more than similar piping types.
This article addresses only some of the multitude of possibilities within piping system designs. They represent the majority of installed system types for larger commercial buildings, but there will always be exceptions to the rules. General master specifications are an invaluable resource when determining piping types for a given system and the associated standards by which to judge each product. Standard specifications will meet the requirements of many projects, but when high-rise towers, high temperatures, hazardous chemicals, or changes in the law or jurisdiction are involved, designers and engineers must review. additional information about piping recommendations and limitations to make informed decisions about the products being installed in their projects. We, as design professionals, are trusted by our clients to provide them with an adequately sized, properly balanced, and reasonably priced design for their buildings—one where the piping systems reach their expected life span and a catastrophic failure is never encountered.
Matt Dolan is a project engineer with JBA Consulting Engineers. His expertise is in designing complex HVAC and plumbing systems for various building types, such as commercial offices, healthcare facilities, and hospitality complexes including high-rise guestroom towers and numerous restaurants.