PEX manifolds and PEX plastic piping offer installation-related cost advantages over conventional rigid pipe plumbing systems. PEX plumbing manifolds and PEX tubing are part of a relatively new method for residential water distribution, but they have gained wide acceptance in the home building industry.
Manifolds serve as control centers that deliver hot and cold water to flexible PEX supply lines running from the manifold to individual fixtures. Each fixture essentially has a home run to the manifold, rather than to a trunk line, as with traditional trunk-and-branch piping.
How a PEX Plumbing Manifold Works
A PEX manifold includes separate manifold chambers to serve hot and cold water lines. The cold-water manifold is fed from the main water supply line, and the hot-water manifold is fed from the water heater. Water pressure in manifolds is maintained by the incoming service line.
A water line dedicated to each fixture originates from a port in the manifold. Manifold plumbing systems can have a single central manifold located at the water service line entry point, or they can have a main central manifold and additional smaller manifolds to service remote fixture groups.
Plumbing manifolds are mounted in a convenient, accessible location, such as a basement wall or a service closet, to allow access for shutting off individual fixtures. If the manifold is plastic, it needs a minimum clearance of 36 inches (vertical) and 18 inches (horizontal) from a water heater. Opposing port-type manifolds can be mounted conveniently between stud framing.
PEX Plumbing Manifold Benefits
There are many benefits associated with both PEX tubing and PEX plumbing manifolds:
- Plumbing manifolds can accept all common supply line sizes, down to 3/8-inches.
- PEX is flexible and can be bent, so fewer fittings are needed than for rigid piping, which means less pressure drop occurs in the lines.
- Flexible PEX piping is a better insulator than copper and is not susceptible to rust.
- Manifold systems cut energy losses as hot water arrives faster at the tap, especially when a loop or ring is added to the system.
- Flexible and non-metallic pipes result in a quiet and efficient plumbing system that doesn’t suffer corrosion, scaling, or microbiological buildup.
- PEX tubing resists freeze damage as it can expand up to 15 percent without bursting.
- PEX plumbing manifold systems can save on labor costs.
- Turning off the supply can be done at a central location.
- Manifold systems are available for commercial distribution nationwide.
How to Install a PEX Manifold
A PEX manifold can be installed at almost any location. Start by counting the number of fixtures or locations where cold and hot water will be used, including any ice makers and outdoor fixtures.
Manifolds include a plate for fastening the unit to a wall or other surface. For best results, keep the following tips in mind:
- Make sure the manifold has enough ports, and identify each one during installation.
- Install the manifold close to the water heater to minimize heat loss.
- Do not install the manifold closer than 18 inches from the water heater outlet.
- Install shutoff valves, making sure there is enough room to operate all valves.
- Most PEX piping manufacturers have their own mechanical fitting and joining methods, so only use materials and tools approved by the manufacturer.
- Use 3/8-inch piping for lower-flow purposes and 1/2-inch piping for higher-flow ones.
- Include extra ports on the manifold for future expansion. Cap off any unused ports.
- Run the PEX piping all the way to the desired location and label the run at the manifold.