Can You Branch Off Hot & Cold Water Lines?

Plumbing Manifolds

• Plumbing manifolds are the new kids on the block. Instead of branching off a main hot water line and a main cold water line, the manifold serves as a central water distribution unit with many flexible water tubes that run to individual fixtures. The manifold panel installs near the hot water heater and both cold and hot water lines connect to the manifold. The panel features multiple red valves along one side and blue valves along the other side. Flexible (PEX) tubes, also in red and blue, which represent hot and cold water, connect to the valves and then run through the walls to reach each fixture.

Hot Water Branches in New Systems

• Typically, the water supply line that feeds the hot water faucet for the kitchen sink branches off to the dishwasher. The standard location of the branch is beneath the sink in an accessible spot. If you're installing a dishwasher, use a connecting fitting that features a shut-off valve. If you have to pull the dishwasher out later, you can turn off the valve without turning off the hot water supply to the sink.

Cold Water Branches in New Systems

• Cold-water branches in manifold systems are usually limited to a “T” that connects to the kitchen sink's cold water supply and runs to a water-filtration system and an icemaker or both. If the cold water runs through a filtration device, such as a reverse osmosis (RO) unit, a tube will then lead from the RO unit to an icemaker. If drinking water is not filtered, the branch for the icemaker will T-off from the cold water supply line just below the kitchen faucet. This branch connection should also have a shut-off valve.

Branches in Old Systems

• Many existing homes don't have manifold systems, so new lines generally branch off the hot and cold water supply lines closest to the new fixture. Many old water supply lines are copper or PVC, and the fittings needed to attach new lines to existing ones are readily available in hardware stores. The general rule is to reduce the size of the line when it branches off a main line to a fixture to ensure adequate water pressure. For example, a main cold water supply line might be 3/4-inch in diameter, but you’ll branch off the line with a fitting that reduces to a 1/2-inch line that connects to the cold-water faucet.