Design Considerations

When designing with PP-R piping systems, it is important to be aware of their unique features such as multilayer faser (MF) for expansion control, proper SDR selection, fusion connections, impact and chemical resistance and sound insulation.

Determining Compatibility

The first step is to verify that PP-R is an acceptable material choice for a particular application. While PP-R pipes are suited to a wide variety of applications, they still have chemical, pressure and temperature considerations that need to be addressed in order to limit the risk of a leak. Operating outside of the safety parameters provided by the manufacturer can shorten the life of the pipe. By bringing a system's intended use in line with the application parameters given in manufacturer documents, engineers can ensure that the pipes will last for many decades.

Suitability. Steam systems, gas systems, water systems with both high temperature and pressure, or systems with high levels of certain aggressive chemicals will likely not be suitable for use with PP-R. Manufacturers offer evaluation for suitability and will confirm which, if any, of the products is suitable for the intended end-use.

In some applications, PP-R pipe may not last as long as it would in a typical plumbing or heating installation, but may still outlast other piping alternatives. Some manufacturers will provide guidance on these applications and performance expectations in these more stringent environments.

Choosing Your System

Although PP-R types share similar characteristics, they are also engineered for use in certain applications. Choosing the correct system for the application will maximize performance and minimize material costs.

As a general rule, green pipe should be used for potable and food-grade applications, while medium-thick blue pipe is used for heating and cooling, compressed air, and a variety of industrial applications. Purple pipe is intended for use in water conservation and gray water systems.

Only multilayer faser pipes should be used on heated or chilled applications, in order to reduce linear expansion.

One manufacturer recommends using the thinnest walled pipe that will meet the temperature and pressure ratings required by the system. Manufacturers' recommended operating parameters typically contain a significant safety factor.

Determining Efficiency

The natural R-value and reduced friction factors are especially important because they reduce the amount of energy needed for the system to perform. With careful planning and engineering, it is possible to exceed existing performance standards and maximize a system's efficiency.

PP-R pipes have a high flow coefficient, and do not suffer from a loss of flow over time due to corrosion. However, for some products the differences in the inside diameter will necessitate flow calculations be made specifically for the PP-R pipe selected. Information regarding flow rates, flow velocity and head loss through fittings can be supplied by the manufacturer.

Integrating With Other Systems

When integrating PP-R piping systems with other systems, it is important to ensure that the operating parameters for PP-R won't damage the other materials or vice versa. Be aware that even if the PP-R pipe is compatible with the chemical being transported, other materials in the system may not be. Make sure that all parts of the system are compatible with the medium being carried before installing them. While PP-R pipe does not require treatment to protect it from corrosion, ferrous metals in the system will. Do not mix PP-R pipe with other piping systems in conditions that will cause the other system to fail.

When there is extensive use of copper piping in conjunction with PP-R, care should be taken to ensure the operating conditions will not cause dissolution or corrosion of the copper. Manufacturers recommend following the Copper Development Association's guidelines for sizing, temperature and flow speed in systems using both copper and PP-R pipe. Copper pipe/tubing should not be used in recirculating domestic hot water systems with PP-R piping.

Planning

All fusion connections require a certain amount of space and mobility around each joint. The amount of space needed for a fusion machine to operate varies by manufacturer and machine type. It is best to confirm that there will be enough space for a machine to operate when planning the installation.

Flame Spread/Smoke

PP-R piping systems do not produce toxic by-products during combustion. In a fully developed fire, PP-R will produce carbon dioxide gas and water vapor. In an under-developed fire, trace amounts of carbon monoxide may be produced, but this is common in all combustible materials including wood and paper. Many building codes do not consider the toxicity of the smoke produced but focus only on the volume and opacity of the smoke. Therefore, it is important to install only pipe that meets local code requirements.

For highly rigorous code requirements, engineers are advised to consult manufacturers for code compliant PP-R solutions.

Plenum Space

When installing PP-R in a plenum space, special considerations need to be taken to meet building codes for flame and smoke limitations. Information regarding plenum-rated options can be found in manufacturers' literature.

Outside Installation

When installed outdoors, with direct sunlight exposure, PP-R pipe will need to be protected from UV radiation since UV radiation can damage and weaken the polypropylene chains over time. Manufacturers can offer guidance on protection solutions such as wraps and paints.

Thrust Blocking

Due to the inherent strength and integrity of fused connections, thrust blocking is not required. Anchors may still be necessary where buried pipe enters a building foundation or other locations to minimize pipe movement.

Fire Stopping

Polypropylene is a combustible material and must be treated as such. Generally, when penetrating a fire-rated assembly, fire stopping must be used to give the penetration a fire rating that matches the rating of the assembly.

It is critical that fire stopping issues be addressed early in the design and construction of a project. Consult with a PP-R producer for a current list of manufacturers who have tested and listed their products for use with PP-R piping systems.

System protection. Allowing a pump to operate for an extended period with zero flow can result in temperatures beyond those recommended. Engineers are advised to provide a sensor system that will warn of temperatures over 180°F, an automatic temperature and pressure relief valve at the pump discharge, or a similar preventative measure.

Vibration Isolation

PP-R can absorb small vibrations, so isolators are not required if the pipe has some limited mobility on either side of the pump. PP-R pipe flowing at 10 ft/s generates less noise than copper pipe flowing at 5 ft/s. 


Noise and Water Hammer

To avoid noise generation and water hammer, the flow rate should not exceed 10 ft/s. Buried pipe or piping in industrial applications may run up to 12 ft/s or higher, depending on the manufacturer's recommendations, as noise generation is typically not an issue.