Question

Class: Hydraulic Engineering

Hot and cold water Plumbing systems. The design criteria and methods?

Answer 1

HOT- AND COLD-WATER PLUMBING DISTRIBUTION:

Hot- and cold-water plumbing distribution within residential and commercial applications has been one of the primary applications for the plastic piping materials represented by PPI's Building & Construction Division since its founding. Plumbing distribution systems transport potable water, also known as drinking water, throughout buildings to end-points such as fixtures, faucets, showerheads, toilets, laundry, dishwashers, hose bibs, and more.

Design criteria :

Introduction
Plastic piping materials have been approved for hot- and cold-water plumbing distribution for decades, and provide economical, safe, sustainable, and reliable plumbing systems without the cost, corrosion, or environmental issues associated with metal piping such as copper.

The plastic plumbing materials represented by PPI are approved in model plumbing codes across USA and Canada.

Materials
Many of the plastic piping materials represented by PPI's Building & Construction Division are intended and certified for hot- and cold-water plumbing distribution. This includes certain CPVC, PEX, PE-RT and PP pipe and tubing materials, as well as PEX-AL-PEX composite materials and the various fittings which are designed for use with each of these piping materials.

These materials must meet specific performance requirements and must carry third party certifications demonstrating they are safe for use in these applications. All products for hot- and cold-water distribution will carry markings indicating they are safe for the intended use.

Please read more about each of these piping materials, including the specific product standards to which they are produced, on the webpages for each of the materials.

Applications
Hot- and cold-water plumbing distribution within residential and commercial applications is one of the primary applications for the plastic piping materials represented by PPI's Building & Construction Division.

Flexible piping materials PEX and PE-RT are commonly installed using one of three main piping configurations as described in various publications:

• Trunk and branch (a.k.a. traditional)
• Parallel (a.k.a. home-run)
• Zoned (a.k.a. remote manifolds)

The more rigid piping materials CPVC and PP are typically installed in trunk-and-branch configurations, though other layouts are possible. It is becoming popular, especially in commercial and large residential applications, for plumbing systems to utilize large diameter CPVC or PP plumbing pipes for risers and headers where rigidity is an advantage, and then to use smaller diameter PEX and PE-RT tubing for the drops or branches to individual outlets, where flexibility may be an advantage.

The publication DESIGN GUIDE for Residential PEX Water Supply Plumbing Systems explains that by applying proper design techniques, PEX plumbing systems can deliver the optimum combination of performance, efficiency, cost and longevity. The other plastic materials can provide similar benefits.

PPI has also published the ASPE-accredited and ICC-accredited courseDesign of PEX Plumbing Systems to Optimize Performance and Efficiency. This course teaches how to achieve these benefits.

Thoughtful design of the hot-water plumbing systems using recirculation loops close to the plumbing outlets (i.e. fixtures) can reduce the wait time for hot water and the associated waste of water. Both the DESIGN GUIDE and the above-mentioned course explain how to achieve this.

Advantages
Plastic pipes don't corrode or suffer scale build-up which can reduce flows. Flexible plastic pipes such as PEX and PE-RT allow for bends and sweeps to be formed by hand, reducing installation time and pressure loss in the piping. And since these plastic materials are inherent insulators, thermal heat transfer through pipe walls is reduced. In addition:

• Plastic plumbing pipes can reduce installation costs while improving long-term performance and reliability
• An optimized intelligent plumbing design can save both water and energy
• Plastic plumbing pipes are quieter and transfer less heat than copper pipes
• The properties of plastic plumbing systems can improve the health, safety and welfare of building occupants through efficient and reliable delivery of clean water.

Dual drinking-water supply systems are those in which two different grades of
water are available in separate piping systems. An example is the provision of a
tap at a sink supplying water directly from the incoming water service while all
other fixtures are fed from a storage tank. In developed countries, the most
common is a secondary system of piping carrying hot water to sink, washbasin
and bath. Occasionally a water softener is installed to treat part of a domestic
system, but apart from these cases dual drinking-water supply systems are rarely
found within single dwellings. An approach to water conservation being
introduced in some communities is to recycle greywater to an outside tap for
irrigation uses. A principal concern of all dual systems is the assurance that no
cross-connections have occurred during installation or repair.

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