Foreword

This webpage contains Frequently Asked Questions (FAQs) about polypropylene pressure piping systems, with answers. This information is offered in good faith and believed to be accurate at the time of its publication. Additional information may be needed in some areas, especially with regards to unusual or special applications. Consult the manufacturer or material supplier for more detailed information. A list of member manufacturers is available on the PPI website (links below). PPI does not endorse the proprietary products or processes of any manufacturer and assumes no responsibility for compliance with applicable laws and regulations.

What is PP-RCT?

• PP-RCT is a high-temperature plastic pressure piping system first used for plumbing and hydronic heating in the 2000s in Europe and introduced to North America in the 2000s
• According to the definition found within industry standard ASTM F2389 (first published in 2004), PP-RCT means polypropylene random copolymer with modified crystallinity and temperature resistance
  • PP-RCT is a copolymer of propylene and at least one comonomer, where the propylene is more than 50% of the composition
  • Commercially available PP-RCT resins may either be alpha-phase crystallinity or a combination of alpha and beta phase crystallinity when using a beta nucleating agent.
• PP-RCT pipes may include reinforcement layers for benefits such as reducing longitudinal thermal expansion/contraction
• With their high temperature and pressure capabilities, PP-RCT pipes are suitable for demanding pressure piping applications
  • PP-RCT pipes are also used in non-pressure applications
• PP-RCT pipes provide resistance to highly acidic and basic solutions, such as corrosion inhibitors and chemicals used in hydronic heating and cooling systems
• Joints are typically heat-fused, following industry practices described below

What are the industry standards for PP-R and PP-RCT?

• ASTM F2389 - Standard Specification for Pressure-rated Polypropylene (PP) Piping Systems
  • Access the latest version here
• ASTM D4101 - Standard Classification System and Basis for Specification for Polypropylene Injection and Extrusion Materials
  • Access the latest version here
• ASTM F3497 - Standard Test Method for Evaluating the Oxidative Resistance of Polypropylene (PP) Piping Systems to Hot Chlorinated Water
  • Access the latest version here
• CSA B137.11 - Polypropylene (PP-R & PP-RCT) pipe and fittings for pressure applications
  • Access the latest version here

What certifications should be expected for PP piping systems?

• NSF/ANSI 14 – Plastics Piping System Components and Related Materials (for all pressure applications)
• NSF/ANSI/CAN 61 - Drinking Water System Components - Health Effects (for potable water applications)
• NSF/ANSI 372 - Drinking Water System Components – Lead Content (for potable water applications)

What are the pressure-temperature ratings for PP-R and PP-RCT piping systems?

• Both PP-R and PP-RCT piping products are rated for pressurized operation at 180ºF (82ºC) temperature
• When SDR 9 (or thicker) wall type is selected, these materials are rated for 100 psi at 180ºF (690 kPa at 82ºC), meeting the requirements of national model plumbing codes
• The actual pressure ratings depend on the selected wall type or thickness
• PP piping materials are available in various wall types and thicknesses (e.g., SDR 7.4, SDR 9, SDR 11, SDR 13.5, etc.), depending on the required pressure rating
  • Thicker-walled pipes have higher pressure ratings, and thinner-walled pipes have lower pressure ratings
• Contact the PP-R and PP-RCT manufacturers listed on this webpage directly to learn about their product offerings

What are the typical applications for PP-R and PP-RCT piping systems?

• Hot- and cold-water plumbing distribution, residential and commercial
• Reclaimed water collection and distribution
• Hydronic distribution to radiators, convectors, fan coils, chilled beams, etc.
• Use as headers for hydronic applications such as radiant heating/cooling, snow & ice melting, turf conditioning
• Distribution pipe and tubing for radiant heating/cooling, snow & ice melting, turf conditioning
• Chilled water and condenser water for cooling towers, data centers, supercomputers
• Industrial and process piping for applications such as semiconductor manufacturing, high-purity pharmaceuticals, and chemical processes
• Gravity and pressurized chemical drainage, such as in laboratories
• Compressed air (when approved by the pipe manufacturer)
• Food processing (when approved by the pipe manufacturer)

Contact the PP-R and PP-RCT manufacturers listed on this webpage directly to learn about their product capabilities and applications

What are the advantages of PP-R and PP-RCT piping systems over traditional metal piping?

• Safety of potable water (when certified to NSF/ANSI/CAN 61) and long-term reliability (when certified to NSF/ANSI 14*)
• Resistance to corrosion, tuberculation, deposits
• Resistance to chlorine and chloramine disinfectants
• Durability and toughness to survive jobsite installations
• Heat-fused joints mean that no flame, glue, or solvents are used for joining
• Lightweight, easy to fabricate off-site, transport, and handle on the job
• Typically reduced product and installation costs as compared with metallic piping systems
• Natural insulator, low thermal conductivity
• No scrap value, avoiding jobsite theft
• Available in wide range of sizes

*Piping products are typically certified to NSF/ANSI 14 for physical, performance, and health effects requirements

What’s the primary difference between PP-R and PP-RCT piping materials?

• Without getting into the chemistry details, PP-RCT material has approximately 25% higher stress capability and a 25% higher pressure rating than PP-R pipes for the same wall thickness at a given operating temperature
• PP-RCT is a newer generation material, somewhat analogous to the newer PE 4710 compounds as compared to PE 3408 piping materials

Are PP-R and PP-RCT pipes and fittings compatible with each other?

• Yes, completely. PP-R pipe can be fused to PP-RCT fittings and vice-versa
• In fact, the recommended fusion procedures are the same for both materials

Should the PP-R / PP-RCT installer follow standard HDPE fusion procedures for PP pipes and fittings?

• The process is very similar, but the temperatures, pressures, machine force, and heating/cooling times are all different for PP, as compared with HDPE; therefore, installers should follow the instructions of the pipe and equipment manufacturer
• PPI members are currently developing an ASTM standard practice for fusion of PP piping systems, analogous to ASTM F2620 for HDPE fusion
• In the interim, the DVS 2207-11 fusion procedures for PP are being used predominantly
• ASTM D2657 Standard Practice for Heat Fusion Joining of Polyolefin Pipe and Fittings may be used for general guidance

Is PP-R or PP-RCT a good pipe for chilled water lines in a factory, such as for injection molding equipment, or in a building, such as for space conditioning?

• Yes, chilled water is a great application for PP piping systems, and there are many successful installations currently operating in North America and around the world

• PP is widely utilized in process water or chilled water systems in a variety of industrial settings, as well as for space conditioning in all types of buildings
• However, at lower temperatures, PP can be susceptible to impact damage
• As long as the pipe is protected against major impact, such as collision by a forklift, backhoe, or similar construction equipment, applications such as this are fairly typical for PP piping systems
• Click this link to a PPI article about this application

How is resistance to disinfectants such as chlorine and chloramines assured by manufacturers?

• According to ASTM F2389, chlorine resistance testing in accordance with ASTM Test Method F2023 is mandatory for PP pipes intended for potable water
• This is the same test method that is used for PEX pipe and tubing, and is used to predict the extrapolated lifetime at an operating condition of 80 psi at temperatures up to 140°F (480 kPa at 60°C) when exposed to hot chlorinated water
• In January 2022, ASTM International published ASTM F3497 - Standard Test Method for Evaluating the Oxidative Resistance of Polypropylene (PP) Piping Systems to Hot Chlorinated Water
• Access the latest version here

Can PP piping materials be installed in return air plenums?

• Yes, when tested with insulation or a fire-rated wrap for flame and smoke testing (e.g., UL 2846 and ASTM E84/UL 723), PP pipes can meet the requirements of building codes for use within return air plenums
• Piping products must be tested according to specific installation methods (e.g., spacing, insulation, fire-wrap), and each manufacturer’s product must carry its own listing for flame and smoke
  • Users and specifiers should review local codes and the specific flame and smoke listing for each piping product
• For hot- and cold-water plumbing distribution, hydronic heating/cooling, chilled water and many other applications, commercial piping materials should be insulated for energy conservation and to prevent condensation on cold water lines

Is UV exposure to PP pipes during construction a concern? What is the allowed exposure time?

• Prolonged exposure to ultraviolet (UV, i.e., sunlight) radiation will discolor bare PP pipe and could weaken the polymer material
• PP pipe and fittings should be protected from UV from the time they leave the manufacturing plant until they are installed, including during storage
• Most manufacturers ship their pipe and fittings in UV protective packaging or wrap that is then removed when installed 
  • If protective packaging is damaged, users should inspect pipes before installation
• Short-term UV exposure such as typically associated with handling and installation at a job site is typically not a problem
  • Most PP pipes and fittings can withstand 3-6 months of exposure without some sort of protection
• PP manufacturers should be consulted for allowable exposure time on the jobsite

Can PP pipes be installed outdoors with continuous exposure to sunlight?

• Some manufacturers provide UV-protected versions of their pipes for outdoor installations, either with an outer protective layer or with UV stabilizers (i.e., inhibitors) blended directly into the pipe material
• Standard PP pipe (without special UV stabilization) can also be protected from UV by wrapping, painting, or covering it with insulation, which is often necessary with heated and chilled water piping for thermal performance and efficiency reasons
  • Primer and paint must be approved by the pipe manufacturer to ensure compatibility
• It is recommended to check with the manufacturer on outdoor installations

How are PP pipes typically connected to existing steel or copper pipes in existing buildings?

• For smaller sizes (i.e., less than 90 mm [4 inch]), a variety of threaded adapters which are fused directly to the PP piping are available
• Flanged adapters are available in most piping sizes from 25 to 710 mm [1 to 28 inch]
  • While PP-R and PP-RCT pipes have a metric outside diameter, PP flange adapters are designed to connect to standard ASME steel flanges
• Grooved fittings are also available in several diameters
• PP manufacturers also offer adapter fittings for solder connections to copper

How are PP pipes typically connected to CPVC, PEX, PE-RT, or PEX-AL-PEX pipes?

• PP manufacturers offer threaded adapter fittings for direct connection to CPVC, PEX, PE-RT or PEX-AL-PEX pipes
• Many also offer fittings that adapt to PEX tubing using crimp (ASTM F1807) and cold-expansion (ASTM F1960) connections

I have seen some PP pipes that appear to have glass fiber in the pipe wall.  Can you explain that?

• Most PP pipe producers manufacture pipes that are reinforced with chopped glass fiber in the middle third of the pipe wall 
• The purpose of the glass fiber layer is to reinforce the pipe for control of longitudinal thermal expansion and contraction 
  • This does not affect the pressure capability
• By incorporating a glass fiber layer, PP pipes have a coefficient of thermal expansion/contraction that is similar to copper pipe
  • The BCD Plastic Pipe Design Calculator can be used to calculate thermal expansion/contraction rates and assist with the design of expansion arms and loops
• The reduced potential for thermal expansion makes this an ideal piping product for industrial or commercial applications, where temperature variation can make control of pipe movement a design challenge

Can PP pipes be direct buried?

• Yes, PP piping systems can be installed underground similar to other plastic pipe using open trench methods
• PP can also be installed using various directional boring methods, but due to the metric outside diameter (i.e., slightly different outside diameters than other pipe types), the pulling heads may require some modification
• Due to the physical properties of the PP materials and the fusion joining process, thrust blocking and thermal expansion compensation are not necessary in most cases
• Consult with the pipe manufacturer regarding maximum pull strength, bending radius, burial depths under roads, and protecting the pipe when passing through foundation walls or other obstructions

What resources are available to help design PP piping systems?

• The BCD Plastic Pipe Design Calculator is a software tool that aids in designing plastic pressure pipe and tubing systems such as PP-R and PP-RCT
• The Calculator includes five main functions:
• Pressure/Head Loss
• Pipe Weight/Volume
• Thermal Expansion/Contraction
• Hydraulic Shock
• Expansion Arm/Loop
• Access the BCD Calculator at this link
• Piping manufacturers often provide design assistance resources such as manuals, guides, and other helpful aids

What other PPI documents related to PP piping systems are available?

• PPI TN-56 Installation of Plastic Pressure Piping Materials Near IC-Rated and Non-IC-Rated Recessed Lighting Fixtures
• PPI TN-57 Proper Integration of Copper Tubing and Components with PP-R Piping Materials for Plumbing Applications
• PPI Statement Y Taste and Odor of Drinking Water from Plastic Piping Systems
• PPI Recommendation G Recommendation Against Using Epoxy Pipe Coatings Within Plumbing Distribution Systems Including Plastic Components
• PPI Recommendation H Recommendation on Direct Connection of Plastic Piping Materials to Tankless Water Heaters for Domestic (i.e. residential) Applications