Why Is My Water Heater Drain Valve Leaking?
A water heater drain valve usually leaks because sediment is stuck in the valve seat so it can't close, the washer inside is worn, the plastic valve body has cracked, or the threads into the tank have loosened. Most drain valve leaks are repairable. Replacing a plastic valve with a brass one is the most common long-term fix, and our drain valve replacement page explains how that job goes.
The drain valve is the spigot near the bottom of the tank, the one you'd attach a garden hose to for flushing. It's a small part, but it sits right where hard-water sediment collects, which is why it's so often the source of water on the floor.
Where Exactly Is It Leaking?
Dry the valve and floor with a towel, then watch for a few minutes. The spot where water reappears tells you what kind of fix you need.
From the spout
Water drips out of the hose outlet. The valve isn't closing fully, usually because of sediment or a worn washer.
Around the handle
Water seeps around the stem or knob. The internal seal is worn. Common on older plastic valves.
At the tank threads
Water appears where the valve screws into the tank. The valve may be loose, or the tank around it may be corroding.
Tip: If the drip is coming from the spout, screw a garden hose cap (a cheap brass or plastic cap from any hardware store) onto the outlet. It won't fix the valve, but it stops the drip until it's replaced.
Hard Water and Sediment: Why This Is So Common Here
Apache Junction's water runs about 13–16 grains per gallon of hardness. As water heats in the tank, calcium and magnesium drop out and settle on the bottom as sediment. The drain valve sits right at that level.
When anyone opens the valve, whether to flush the tank or just to test it, sandy bits of scale rush through and can lodge in the seat. The valve then won't seal no matter how hard you turn it. Overtightening a plastic valve to stop the drip can crack it, which makes things worse.
Can flushing the valve stop the leak?
Sometimes. Opening the valve fully for a few seconds with a hose attached can wash out a piece of grit stuck in the seat. If the drip stops after you close it again, you're done. If it keeps dripping, the washer or seat is damaged and the valve needs replacing. Read more on our Apache Junction hard water page.
Plastic vs Brass Drain Valves
Many water heaters come from the factory with a plastic drain valve. They work, but they don't hold up well to hard water, heat and repeated flushing.
| Plastic valve | Brass valve | |
|---|---|---|
| Durability | Can crack with heat, age or overtightening | Much more durable |
| Sediment | Small opening clogs easily | Full-port ball valve styles pass sediment much better |
| Flushing | Slow, often clogs mid-flush | Faster, easier yearly flushes |
| Removal | Can snap off in the tank threads | Unthreads cleanly when needed |
If you flush your heater every year, which we recommend with water this hard, a brass full-port drain valve makes the job much easier and much less likely to leave you with a drip afterward.
How a Drain Valve Gets Replaced
- Turn off the heat and cold water. Breaker off for electric, gas knob to "Pilot" or "Off" for gas.
- Let the water cool if possible, then open a hot faucet in the house to let air in.
- Drain the tank through the old valve with a hose to a drain or outside. If it's clogged with sediment, a backflush with short bursts of cold water can break it loose.
- Remove the old valve. Plastic valves sometimes break and have to be carefully cut out without damaging the tank threads.
- Install the new brass valve with thread sealant, then refill the tank with a hot faucet open until water runs smoothly.
- Check for drips, then restore power or relight the pilot.
Is this a good time to flush the tank?
Yes. With the tank already drained, rinsing out sediment until the water runs clear is a smart extra step. It quiets a rumbling tank and helps it heat more efficiently.
When is a drain valve leak a bad sign?
If water is coming from the tank wall around the valve threads, and the area is rusty, the tank itself may be corroding. On an older heater, that can mean it's time to replace rather than repair. See our water heater tank leaking page and our repair or replace guide.
Make Sure It's Really the Drain Valve
Water at the bottom doesn't always come from the drain valve. The relief valve pipe also ends near the floor, and drips from fittings up top can run down the tank. Check the end of the relief pipe and the top connections too. Our water heater leaking from bottom page and leak finder walk through every spot.
Apache Junction Water Heater Pros replaces drain valves, flushes tanks and handles every other kind of leak, 24 hours a day. You can see everything we fix on our water heater repair in Apache Junction page, or go back to our Apache Junction leak repair homepage.
Drain Valve Leaking FAQs
Is a leaking water heater drain valve an emergency?
Usually not. A drain valve drip is typically slow. Put a bucket or pan under it, or screw a hose cap on the outlet, and schedule a repair. If water is pouring out, or it's coming from rusted tank metal around the valve, turn off the water and call.
Why did my drain valve start leaking after I flushed the tank?
Sediment from the bottom of the tank likely got caught in the valve seat when you opened it. Try opening it fully again for a few seconds to wash it out. If it still drips after closing, the valve needs to be replaced.
Can I tighten a leaking drain valve?
If the leak is at the threads where it meets the tank, a gentle snug may help. If water drips from the spout or around the handle, tightening won't fix it. Be careful with plastic valves, which crack easily when overtightened.
Do I have to drain the tank to replace the drain valve?
Yes. The valve is at the bottom of the tank, so the tank has to be drained first. That makes it a good time to flush out sediment too.
What kind of drain valve is best for hard water?
A brass full-port ball valve. It's much more durable than plastic and has a wider opening that lets sediment pass, so it's less likely to clog or drip after flushing. That matters in Apache Junction's 13–16 grain water.
How often should I flush my water heater in Apache Junction?
Once a year is a good rule with water this hard. If you hear popping or rumbling when the heater runs, sediment has built up and a flush is overdue.