6 Ways to Unclog a Water Heater That Won’t Drain

It’s maintenance season at your house again, and you’re running through the checklist one appliance at a time. This time, the goal is to flush your water heater so you set up the hose and prepare for a flush only to find your water heater won’t drain. How are you supposed to remove the sediment when it’s not draining?

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This problem is a lot more common on older models which lack many of the additional anti-sediment features of the newest top-line heaters. More frequent drainings or adding components to help filter incoming water can help prevent future clogs. Meanwhile, there are two approaches to unclogging the drain valve, based on whether the water is still hot.

Hot Water Methods

These solutions won’t require you to cool the tank off first, but can also increase the risk of getting burned. Be sure to wear protective clothing and exercise caution when trying these methods.

Back Flushing

You’ll need a washer fill hose for this trick, as it has female connections on both ends. Attach one end to the drain valve and the other to your washtub or other nearby faucet. Then, open the drain valve and turn on the water.

The water pressure will push its way up through the sediment, dislodging the clog. After a couple minutes, shut off the water, close the valve, and remove the hose to begin regular drainage.

water heater won't drain

Forced Air

While you might not think of it as such, the drain is a two-way valve. If the drain valve clogged before or during your drainage attempt, you can simply slam your foot down on the hose. This causes a burst of air to enter the tank, pushing away debris.

Usually, this is enough to get the water flowing again and is easy to repeat as needed. Kink-proof hoses may not allow this method, but it can be very effective when using standard garden hoses.

Patience

When the tank is draining slowly, there’s a chance your clog will work itself out. It might take an hour or two, so just check back occasionally to ensure the water’s still coming out (or if the clog was dislodged).

Note that this method is the least effective and won’t work against heavy buildup, as more sediment can easily fall into the clog.

Cold Water Methods

These methods will often require you to be very close to the drain valve. For this reason, we strongly suggest shutting the hot water tank off for up to 24 hours. Using the hot water taps in the house will help reduce the tank water’s temperature a little faster, as the used hot water’s being replaced by cold.

Coat Hanger Fishing

Ah, the ever-trusty wire coat hanger. This tool is almost as vital to any tool kit as duct tape. Begin by putting some towels down, as this could get a little messy. Next, open the drain valve and slip the wire in, moving it in a circular motion to dislodge the debris.

Once it starts flowing, shut the drain valve off long enough to attach your hose. You can always repeat the procedure if the clog reforms before you’ve finished draining.

how to unclog water heater

Drain Valve Replacement

Sometimes the problem isn’t actually a clogged water heater, but a defective valve. You can remedy this situation by replacing the drain valve – even when the tank’s still full. You’ll want to ensure all of the faucets in the house are off so that air can’t get into the tank while you’re working. The resulting vacuum can keep the tank from gushing all over the place.

Add some teflon tape to the threading of the new drain valve. This adds an extra layer of waterproof sealing. Next, gently unscrew the defective valve, being ready for some leakage. Once the valve’s loose, quickly change it out for the new one to minimize the amount of escaping water. Once done, you can flush as you normally would.

drain directly into garage drainOpen Flushing

In the event you have a floor drain beside your water heater, you can simply remove the drain valve and allow the water to gush out. While not an ideal solution, it gives you easier access to the clog, so you can make a more successful fishing attempt with your coat hanger.

Be warned, this method is quite messy, but can also be one of the most effective.

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