Cross-Linked Polyethylene (PEX) Part 2 of 2
Cross-linked polyethylene (PEX) is growing quickly in acceptance as a supply pipe for residential plumbing.
Cross-linked polyethylene (PEX) is growing quickly in acceptance as a supply pipe for residential plumbing. It’s not hard to understand why. Developed in the 1960s but relatively new to the United States, this supply pipe combines the ease of use of flexible tubing with the durability of rigid pipe. It can withstand a wide temperature range (from subfreezing to 180° F); it is inexpensive; and it’s quieter than rigid supply pipe.
PEX is flexible plastic (polyethylene, or PE) tubing that’s reinforced by a chemical reaction that creates long fibers to increase the strength of the material. It has been allowed by code in Europe and the southern United States for many years, but has won approval for residential supply use in most major plumbing codes only recently. It’s frequently used in manufactured housing and recreational vehicles and in radiant heating systems. Because it is so flexible, PEX can easily be bent to follow corners and make other changes in direction. From the water main and heater, it is connected into manifold fittings that redistribute the water in much the same manner as a lawn irrigation system.
For standard residential installations, PEX can be joined with very simple fittings and tools. Unions are generally made with a crimping tool and a crimping ring. You simply insert the ends of the pipe you’re joining into the ring, then clamp down on the ring with the crimping tool. PEX pipe, tools, and fittings can be purchased from most wholesale plumbing suppliers and at many home centers. Coils of PEX are sold in several diameters from 1⁄4" to 1". PEX tubing and fittings from different manufacturers are not interchangeable. Any warranty coverage will be voided if products are mixed.
PEX pipe is a relatively new water supply material that’s growing in popularity in part because it can be installed with simple mechanical connections.From: The Complete Guide to Plumbing, 978-1-58923-378-2
Home run systems rely on one or two central manifolds to distribute the hot and cold water very efficiently. Eliminating the branch fittings allows you to use thinner supply pipe in some situations.
Remote manifold systems are a hybrid between traditional trun-‑and-branch systems and home run systems. Instead of relying on just one or two manifolds, they employ several smaller manifolds downline from a larger manifold. Each smaller manifold services a group of fixtures, as in a bathroom or kitchen.
Choosing a PEX system
Choosing a PEX system
• For maximum single-fixture water pressure: Trunk and branch
• For economy of materials: Trunk and branch or remote manifold
• For minimal wait times for hot water (single fixture): Home run
• For minimal wait times for hot water (multiple fixtures used at same approximate time): Trunk and branch or remote manifold
• For ease of shutoff control: Home run
• For lowest number of fittings and joints: Home run