What Is a Water Manifold?

A very simple example of a water manifold is the multiport outlet you screw onto an outdoor water spigot to allow you to connect several hoses to the same spigot. It has a single inlet port, which connects to the spigot, and two, three, four, or more outlet ports, each with its own hose connector and shutoff valve.

The same basic idea is employed for a water manifold for a house. A manifold is commonly found in homes with hydronic heating systems because it allows users to control the amount of heat in various parts of the house. It's also a staple in PEX plumbing systems because it allows all plumbing fixtures to connect to a central control station, which greatly simplifies repairs.

Manifolds for hydronic heating systems are often made from brass or stainless steel, while those for PEX water systems are more often made from copper. They are cylindrical and look very much like multiport hose outlets except they are larger and there are two of them: one for hot water and one for cold.

Cold water enters the inlet of the cold manifold — which usually has a 3/4-inch connector — directly from the water supply and exits from the outlets, each of which is connected to a 3/8-, 1/2-, or 5/8-inch cold water branch pipe. Hot water comes either from a water heater or boiler — depending on whether it's supplying a potable water system or a hydronic heating system — and flows through the manifold outlets to individual plumbing fixtures or heating elements.

The number of outlet ports depends on the size of the house and the number of plumbing fixtures or heating elements. Small manifolds may have only eight outlets, equally split between hot and cold, while large ones can have as many as 20. It's common for PEX manifold systems to have blue pipes for cold water and red for hot so you can tell them apart, but when copper pipes are used, they are all the same color: copper brown.

Although it looks complicated with all its incoming and outgoing pipes, the operation of a manifold system is pretty straightforward. Each outlet has a valve to control or stop the flow of water. This may be electronic or manually operated, and the valve usually includes a backflow preventer to keep water flowing in only one direction.

The main advantage of hydronic manifold systems is that they allow for multizone heating throughout the house. They often have electronic valves that allow for automatic and precise temperature control in individual zones.

A hot and cold water manifold for a PEX water system allows plumbers to run tubing from a central location to each water fixture, which is a snap to do with PEX because it's so pliable and easy to run through framing. This eliminates the need for connectors inside the walls that can rupture and leak and makes it easier to do repairs. When a fixture needs to be repaired or replaced, you can turn off the valve in the manifold that supplies that fixture and leave the water to all the other fixtures on.