Flushing a water heater is a DIY job many homeowners can do safely if they follow precautions and their unit’s manual. Below is a clear, step‑by‑step guide plus some safety notes.

Safety first

Before you touch anything, keep these in mind:

  • Turn off power or gas to the heater so it cannot heat while empty.
  • Hot water can scald; let the heater cool for a while if it has been running.
  • Know where your main water shutoff is in case a valve leaks or breaks.
  • If your heater is old and valves are corroded, consider calling a plumber; drain valves sometimes fail when first used in years.

What you’ll need

  • Garden hose long enough to reach a floor drain or outside.
  • Bucket (optional, to check sediment and water clarity).
  • Flathead screwdriver (often needed to open the drain valve).
  • Towels or rags in case of minor leaks.

Steps to flush a tank‑type water heater

These steps apply to typical gas or electric tank heaters; always adjust to match your manufacturer’s instructions.

1. Shut off heat and water

  1. For an electric heater, switch off the breaker feeding the water heater.
  1. For a gas heater, turn the thermostat to “Pilot,” “Vacation,” or completely off depending on the label.
  1. Close the cold‑water inlet valve at the top of the tank so no new water enters the heater.

2. Open a hot tap for air

  • Go to a nearby sink or tub and open the hot water faucet.
  • This lets air into the system so the tank can drain instead of “vacuum locking.”

3. Connect the drain hose

  1. Locate the drain valve near the bottom of the tank.
  2. Screw the garden hose onto this valve tightly.
  1. Run the other end of the hose to a floor drain, sump pit, driveway, or safe outdoor spot where hot water will not damage plants or surfaces.

Make sure the hose end is lower than the tank outlet if you’re using gravity to drain; this helps the water flow steadily.

4. Drain the tank

  1. Carefully open the drain valve using the handle or a flathead screwdriver.
  1. Water should begin flowing through the hose; it may start out dark or cloudy if there’s heavy sediment.
  1. Let the tank drain until the flow slows to a trickle or stops.

If water does not flow:

  • Sediment may be clogging the valve; some DIYers briefly open the cold inlet to push sediment out, but if it feels stuck or unsafe, call a pro.

5. Flush out sediment

Once the tank is mostly empty, you’ll actually “flush” it:

  1. Leave the drain valve open with the hose still attached.
  2. Briefly open the cold‑water inlet at the top of the tank for 15–30 seconds; this rush of water stirs up sediment and pushes it out the hose.
  1. Close the cold‑water valve and let the tank drain again.
  2. Repeat this fill‑and‑drain cycle until water coming from the hose runs clear, with little or no grit at the bottom of your bucket if you’re catching some to inspect.

Some homeowners also do one complete fill and drain at the end to be sure most sediment is gone.

6. Close up and refill

  1. When the water runs clear, close the drain valve tightly and remove the hose.
  1. Make sure the hot water faucet in the house is still open.
  2. Open the cold‑water inlet valve fully to refill the tank.
  1. As the tank fills, air will blow out of the open hot faucet; once you get a smooth, steady stream of water (no spurts), the tank is full.
  1. Turn off the hot faucet.

7. Restore power or gas

  • For electric: Only after the tank is completely full, turn the breaker back on; running elements in an empty tank will burn them out.
  • For gas: Turn the control from “Pilot/Vacation” back to your normal temperature setting.

Check around the drain valve and piping for leaks over the next hour or two.

Tankless water heaters (short note)

Tankless units are flushed differently, usually with a pump and a descaling solution circulating through service valves for about 45 minutes. This is more like “descaling” than draining, and you should follow the specific kit and manufacturer instructions or hire a pro.

How often should you flush?

  • Many plumbers recommend flushing a traditional tank heater about once a year; more often if you have very hard water.
  • Regular flushing removes mineral sediment, helps maintain efficiency, and can extend the heater’s lifespan.

Quick HTML summary table

html

<table>
  <thead>
    <tr>
      <th>Step</th>
      <th>Action</th>
      <th>Key Points</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>1</td>
      <td>Shut off power/gas and cold water</td>
      <td>Turn off breaker or set gas to Pilot/Off; close cold inlet valve at top of tank.[web:1][web:5][web:7]</td>
    </tr>
    <tr>
      <td>2</td>
      <td>Open a hot faucet</td>
      <td>Opens system to air so the tank can drain freely.[web:1][web:7]</td>
    </tr>
    <tr>
      <td>3</td>
      <td>Attach hose to drain valve</td>
      <td>Connect garden hose to valve near bottom; route to safe drain or outside.[web:1][web:5]</td>
    </tr>
    <tr>
      <td>4</td>
      <td>Drain the tank</td>
      <td>Open drain valve carefully; allow water and sediment to exit until flow slows.[web:1][web:5][web:7]</td>
    </tr>
    <tr>
      <td>5</td>
      <td>Flush with fresh water</td>
      <td>Open cold inlet briefly in bursts with drain open until water runs clear.[web:1][web:5][web:7][web:8]</td>
    </tr>
    <tr>
      <td>6</td>
      <td>Close valve and refill</td>
      <td>Close drain, remove hose, open cold inlet fully; leave hot tap open until flow is steady.[web:1][web:7][web:10]</td>
    </tr>
    <tr>
      <td>7</td>
      <td>Restore power/gas</td>
      <td>Once full, turn breaker or gas control back to normal temperature.[web:5][web:7][web:10]</td>
    </tr>
  </tbody>
</table>

Information gathered from public forums or data available on the internet and portrayed here.