Glossary
Dip Tube
Plastic tube inside a water heater that delivers cold water to the bottom of the tank so it heats thoroughly before mixing with hot water at the top.
The dip tube is a plastic pipe—usually PVC or polybutylene—that runs from the cold-water inlet down to near the tank bottom. Without it, incoming cold water would mix immediately with the hot water at the top, killing efficiency and giving you lukewarm water fast.
When the dip tube fails or cracks, cold water enters at the top and mingles with stored hot water, cutting the usable hot-water volume in half or worse. You'll get complaints about short showers and no recovery time. The tank may still heat up, but the stratification—the separation that lets hot water sit at the top—collapses.
Dip tubes can fail from chlorine degradation in municipal water or from mineral buildup if the water is very hard. If a customer reports sudden loss of hot water without a temperature or thermostat problem, a failed dip tube is your first suspect. Replacement means draining the tank and unscrewing the nipple at the cold inlet, then threading in a new dip tube—straightforward but time-consuming on an installed unit.