Water Heater Leaking from Drain Valve? Here's What To Do (2024)

Relegated to a closet or a basem*nt corner, a water heater lives a secluded life of quiet service, and its warning signs often go unheeded. For example, when enough sediment collects on the bottom of the tank to interfere with heating, a water heater may produce popping and crackling sounds. Most homeowners never get close enough to hear these sounds, which could be signs of an impending leak or one that has already started.

Sediment can also gum up the drain valve and cause leaks. You might get lucky and find a way to stop such a leak by tightening something, but for a long-term fix, master plumber Roy Barnes advises that replacing the valve is usually the best option. And while you’re at it, you can flush out that sediment. When I put on my plumbing hat, that’s something I’ve done on several occasions.

This post explains how to identify a leaking water heater drain valve and what to do about it.

What Is a Water Heater Drain Valve?

Tank-style water heaters (not on-demand ones) store water in a glass-lined steel tank. The drain valve is a spigot installed on the side of the tank near the bottom.

The valve may be made of plastic, but the best ones are brass. “Existing valves on most water heaters are not full port valves,” says Barnes. “This means they are not the actual pipe diameter and will hold debris while trying to drain the tank.” If you haven’t flushed your water heater for a while, and sediment has built up, you may find that the tank takes a long time to drain. That’s another sign that it’s time to replace the valve.

Signs of a Leaking Drain Valve

Water on the floor at the water heater’s base is a sure sign of a leak. The water might be coming from the temperature and pressure relief valve (T&P valve), though.

To make sure the drain valve is the culprit, look for signs of active leaking from that valve. You might see drips or even a steady stream of water flowing from the spout, handle or gasket connecting it to the tank.

• Pro tip: If the T&P valve leaks, it could indicate dangerously high pressure in the tank. Lower the temperature to 120 F and note whether the leak stops. If not, the valve may have been compromised by scale, which is preventing it from closing all the way, and it probably needs to be replaced.

What Causes a Drain Valve to Leak?

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Water heater drain valves are usually screwed in tight enough at the factory to prevent leaking from the threads. However, if you see water dripping or spraying from the base of the valve, where it connects to the tank, it could be slightly loose. You might be able to stop the leak by tightening the valve with a pipe wrench, but be careful not to overdo it. You could break the valve, and if the tank is full of hot water, that’s dangerous. As a precaution, you should turn off the gas or electricity and let the water cool before you attempt this.

When a valve leaks from the spout, the cause is usually sediment or scale collecting inside the valve housing, preventing the valve from closing all the way. If your tank has a compression-style valve that you have to rotate through multiple turns to open and close, it may leak from the handle because the packing is worn out.

How to Replace the Drain Valve on a Water Heater

You’ll need to turn off the water heater and the cold water valve, let the water cool and drain the tank before you can replace the drain valve (so prepare to be without hot water for at least the rest of the day). Here’s a quick rundown of the procedure:

1. Attach a hose to the drain valve, open the valve, and let water flow out to a place from where it can drain safely. You’ll need to let air into the tank to displace the water, and in most cases, you can do this by opening hot water faucets in the house.
2. Put a bucket under the valve to catch residual water and unscrew the valve using a pipe wrench.
3. Prepare the new valve. Barnes recommends assembling a brass nipple and a full-port valve rather than installing a standard drain valve. “A full-port valve is the actual diameter of the pipe, which will allow you to drain sediment and larger debris through that line.”
4. Screw the nipple into the tank and tighten it. Screw the valve onto the nipple, and screw a hose adapter onto the valve outlet, so you can attach a garden hose.
   • Pro tip: Don’t forget to seal all thread connections with plumbing tape or pipe dope.
5. Close the new drain valve and all the faucets you opened, turn on the cold water and let the tank fill. Finish up by turning the water heater back on.

When to Call a Plumber to Fix a Leaking Drain Valve

You may need a plumber’s assessment of the situation if you see water leaking from any place other than the drain valve or T&P valve. Additionally, don’t hesitate to call a plumber if the drain valve breaks when you’re trying to remove it or if you notice excessive corrosion on the threads.

How Much Does It Cost to Replace a Water Heater Drain Valve?

Plumbers charge from $75 to $150 per hour, and the actual procedure for swapping out the drain valve shouldn’t take much more than an hour. You can avoid extra charges by draining the tank yourself. If the plumber has to do this, you’ll probably have to pay for one or more hours of labor.

FAQs

Can you cap a leaking drain valve?

Yes. You can screw a brass garden hose end cap onto the hose threads. If the valve is leaking from the spout, this should stop the leak.

Can you replace a drain valve without draining the water heater?

No. Draining the tank is an absolute prerequisite to replacing the drain valve. If you have to replace the T&P valve, you only need to partially drain the tank until the water level is below the level of the valve.

Do all water heaters have a drain valve?

Yes, every tank-style water heater has a drain valve. If it didn’t, you wouldn’t be able to empty the water, so you can move it.

About the Expert

• Roy Barnes is co-owner of Maryland-based Service Force Plumbing together with his partner, Hendrik Vandepoll. He has been in the trade for 30 years.