- DIY difficulty
- Easy
- Time
- 1–2 hours
- Parts cost
- Brass drain or ball valve
- Pro price
- $225
Tools & materials
- 3/4" brass drain valve or full-port ball valve
- Adjustable or pipe wrench
- Thread-seal tape
- Garden hose
- Bucket and towels
Try the quick fix first
Sediment often keeps the valve from sealing. Attach a hose, open the valve fully for 10–20 seconds to flush debris, then close it firmly (don’t force it). A threaded hose cap with a rubber washer is a cheap stopgap for a slow drip.
How to replace a water heater drain valve
- Turn off the heat: gas to “Pilot” or “Off,” or electric at the breaker. Let the water cool for a few hours to avoid scalding.
- Shut the cold-water supply and open a hot tap in the house.
- Drain the tank completely through a hose to a floor drain or outside.
- Unscrew the old valve counter-clockwise. Plastic valves can snap, so turn gently and remove any broken pieces from the threads.
- Install the new valve. Use 3–4 wraps of thread-seal tape, then tighten so the outlet points down or out.
- Refill: close the new valve, open the cold supply, and run the hot tap until air stops sputtering. Check for leaks, then restore the heat.
Electric heaters: never turn the power back on until the tank is completely full, or you’ll burn out the heating elements.
Flushing sediment while you’re at it
With the tank drained, open the cold supply for a few seconds at a time to stir up and push out sediment, until the water runs clear. A yearly flush can reduce rumbling noises, help efficiency, and extend tank life. It’s also a good moment to check the anode rod.
When to call a pro
- The valve snapped off inside the tank fitting.
- The tank won’t drain because it’s clogged with sediment.
- Water is leaking from the tank itself, not the valve. That means it’s time for a water heater replacement.
Frequently asked questions
Why is my water heater drain valve leaking?
Plastic factory drain valves wear out, crack, or get sediment stuck in the seat. Try opening and closing the valve a few times to flush debris, and make sure it’s fully closed. If it still drips, replace it with a brass valve.
Do I have to drain the whole tank to replace the drain valve?
Yes. The drain valve is at the bottom of the tank, so the tank must be completely drained first. That’s a good time to flush sediment too.
Should I upgrade to a brass or ball-valve drain?
Yes. A full-port brass ball valve drains faster, clears sediment better, and is much less likely to leak than a plastic valve.
How often should I flush my water heater?
Most manufacturers recommend flushing at least once a year, and more often with hard water. Check your owner’s manual.