A hot water tank is a hardworking appliance that provides a constant supply of heated water for daily household needs. Over time, mineral deposits and sediment accumulate inside the tank, which can compromise its performance. The process of flushing, or draining and cleaning, the tank removes this buildup. This routine procedure is necessary to maintain the unit’s efficiency and ensure a reliable supply of hot water.
Why Flushing is Essential
The water supplied to a home contains dissolved minerals, primarily calcium and magnesium, which are known as hardness minerals. When water is heated inside the tank, these minerals precipitate out and settle at the bottom, forming a layer of sediment. This layer acts as an insulator, separating the heating element or gas burner from the water it is meant to heat.
The insulating effect forces the heating system to operate for longer periods to reach the thermostat’s set temperature, which reduces energy efficiency and increases utility costs. Sediment buildup also causes the metal at the bottom of the tank to overheat, leading to premature wear and a shortened lifespan. Warning signs that a flush is needed include rumbling or banging noises caused by water trapped in the sediment layer boiling. Other indicators are reduced hot water output, rusty or cloudy water, and foul odors.
Safety and Preparation Checklist
Before beginning the flushing process, it is mandatory to disable the heater’s power source to prevent damage and ensure safety. For an electric water heater, the circuit breaker controlling the unit must be switched off at the main panel. If the unit is gas-powered, the gas valve on the tank should be turned to the “Pilot” or “Off” position to extinguish the burner.
The cold water supply valve, typically located above the tank, must be closed to stop new water from entering the system. Gathering the necessary tools, such as a garden hose, a bucket, and a flathead screwdriver or valve wrench, should be done next. Finally, open a hot water faucet somewhere in the house to relieve pressure and prevent a vacuum from forming as the tank drains.
The Step-by-Step Flushing Process
With the power and water supply secured, the next step is to attach the garden hose to the drain valve, which is located near the bottom of the tank. The other end of the hose should be routed to a safe drainage area, such as a floor drain or outside, ensuring the hose can handle the temperature of the hot water. Once the hose is secured, open the drain valve, often using a flathead screwdriver to turn the plastic or brass fitting, and allow the tank to empty completely.
The water draining from the tank will be hot and may contain visible sediment, which can take 20 to 60 minutes depending on the tank size and the amount of buildup. Once the tank is empty, the “power flush” technique is used to dislodge any remaining sediment that may be stuck. This involves briefly opening the cold water supply valve for a few seconds to send a surge of water into the tank, agitating the sediment, and then closing it again. This process should be repeated until the water flowing out of the hose runs visibly clear, indicating the tank is clean. After the water runs clear, the drain valve must be closed tightly, and the garden hose can be disconnected.
Restarting Your Heater and Maintenance Schedule
The tank must be refilled with water before the heating element or burner is reactivated to prevent immediate damage. To refill the tank, open the cold water supply valve that was previously closed. Water will begin to flow into the tank, and air will be pushed out through the open hot water faucet in the house. Once a steady, air-free stream of water flows from the open faucet, the tank is full, and the faucet can be closed.
Before restoring power, check the drain valve for any leaks, as sediment can sometimes prevent it from sealing properly. If no leaks are present, the final step is to turn the power back on at the circuit breaker for electric units or turn the gas valve back to the “On” position for gas units. For most homes, flushing the hot water tank annually is sufficient to maintain efficiency. However, if the home is supplied with particularly hard water, a maintenance schedule of every six months is recommended to prevent excessive mineral accumulation.