How to Drain a Water Heater the Right Way

Josh Miller

Josh is a contributing writer to the site and former HVAC specialist.

Last Updated on June 3, 2021

Tank water heaters have to be drained and flushed at least once a year. Sediments can accumulate inside the tank, causing corrosion and damaging the heating element.

Conventional water heaters are pretty durable and don’t require as much maintenance as tankless water heaters, but they still need proper care.

People that delay maintenance eventually find that their tank water heater has become inefficient. Sediment buildup on the inside slowly damages the heating element and reduces its power. Even worse, corrosion on the tank’s inner lining can eventually break the tank and flood your attic or basement, costing you thousands in repairs. 

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Table of Contents

Why You Should Drain Your Water Heater

The main reason why it’s critical to drain and flush a conventional water heater every year is to clean the inside. Water carries minerals such as calcium and magnesium that cause scale buildup and rust inside a tank.

The sediments settle primarily on the bottom, although they also stick to the side of the tank. Over time, the collected sediment deposits inside the tank can slowly damage the heating element and the tank’s inner lining. This is an especially pernicious problem in areas with hard water, which carries an above-average amount of minerals. 

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Do Tankless Water Heaters Have to be Drained?

Tankless water heaters don’t require draining, although they still need cleaning, just like conventional water heaters. Cleaning your tankless water heater is vital to its longevity. Without proper care, they start malfunctioning in just a matter of years.

A tankless water heater doesn’t store water in the same way as a conventional water heater. Instead, it simply heats water on demand and sends it through the house when you open a hot water faucet. Because no water is stored in the tank, there’s nothing to drain when you clean them.

How Do Conventional Water Heaters Work?

Conventional water heaters work by storing hot water. When you open a hot water faucet, you slowly use all of the supply in the tank until there isn’t anything left.

As hot water empties, the tank starts filling up again with cold water. When the temperature inside the tank drops below around 120°F, the tank’s thermostat notices, and the tank starts heating the water again.

The heating element is at the bottom of the tank, where most sediment tends to collect. Without draining and flushing a water heater, the heating element gets damaged by sediment buildup, and the tank becomes inefficient.

How to Drain a Tank Water Heater in 6 Simple Steps

Before cleaning and flushing a water heater, you must drain all the water inside. Follow these simple steps to learn how to drain a water heater.

Step 1: Turn off the energy source

There are two types of tank water heaters: gas and electric. If your water heater is electric, find the breaker and turn it off, or simply unplug the water heater from the wall. If you have a gas water heater, you should turn off the gas valve. Usually, this valve is located on top of the water heater.

Instead of turning off the gas, some people change the settings on the thermostat to pilot or vacation mode. This prevents the burner from turning on and ruining the tank during the process. However, you might find it easier simply to turn off the gas and thermostat completely.

Step 2: Turn off the cold water supply

The cold water valve is usually located on top of the tank, but it can be on its right or left side depending on the installation. Turn off the valve entirely, so there’s no cold water entering the tank.

Step 3: Connect a garden hose to the drainage spigot

There’s a small drainage valve or spigot down near the bottom of the tank. Connect a garden hose to the drainage valve, but don’t open the valve yet. Make sure it’s nice and tight, using proper threading. Leave the opposite end of the hose out in the garden or a large bucket.

Step 4: Open a hot water faucet

The main objective is to get water out of the tank through the hose. However, water isn’t going to start flowing out yet because there’s no air coming into the tank. It’s a bit like holding the liquid in a straw with your thumb over one end. To get water flowing, open a hot water faucet anywhere in the house.

Step 5: Open the pressure relief valve

When you open a faucet, open the drainage valve and see if water starts flowing. If you don’t hear or see any water flowing, you might need a little more air inside the tank. The way to do this is by using the pressure relief valve.

You should be careful with the pressure relief valve because it’s an important safety feature of your tank. When the pressure inside the tank becomes dangerously high, this valve automatically opens and lets some hot water out. There’s a small arm on the valve, and you have to lift it to open the valve.

Now the water should start flowing out from the tank.

Step 6: Wait for the water to drain

The water coming out of the tank will be very hot. Use caution and ensure no one is near the hose or bucket. The draining process should last about 20 minutes.

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Why You Need to Clean the Tank After Draining

When learning how to drain a water heater, it’s essential to know how to flush the tank as well. Usually, the whole point of draining a water heater is to clean the inside.

Draining the water from the tank won’t cause enough pressure to release sediments stuck on the inside. Opening the cold water valve for about 15 minutes sprays water into the bottom of the tank and helps release a lot of the sediments. If you take a look at the bucket on the other end of the hose, you should be able to see deposits coming out.

Repeat this process 3 or 4 times. You can also remove the drainage valve with a wrench and clean the inside of the tank with a long narrow brush.

Drain and Flush Once a Year For Maintenance

There’s one more thing you can do to improve the durability of your water heater. You can install an anode rod inside the tank, which attracts corrosive minerals and prevents them from damaging the inside. Because the rod receives all the corrosion damage, you must replace it every 3 to 5 years.

In addition to installing an anode rod, drain and flush your water tank at least once a year. This keeps your tank in excellent condition, preventing problems like inefficient heating and flooding.

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