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How to Drain a Water Heater

So you want to drain your water heater. First, let’s take a step back. This process differs slightly depending on what type of water heater your house is equipped with, the hardness of your water, and the purpose behind draining the system.

Why Drain Your Water Heater?

Water heaters need to be drained for two main reasons:

  • There is a clog
  • Preventative maintenance

Your water heater unit intakes water from your main water line, which can contain various types of sediment such as sand, gravel, dirt, and mineral deposits. Water heater clogs happen more frequently in areas where the water has a high mineral content, but they can also occur when regular maintenance (flushing) is not performed. Draining your electric or gas water heater regularly can extend its lifespan and lower your energy bills (unclogged water heaters don’t have to work as hard!).

Most water heater manufacturers recommend draining your water heater regularly – frequency is determined by how high the mineral content in your local area is[1].

Find the Mineral Content of Your Area’s Water

If you don’t already know the quality of the water in your area, you can purchase a home water quality test kit for relatively cheap. Most of these home test kits give readings on things like bacteria, lead, chlorine, hardness, and pH. You’ll want to concentrate on water hardness, which is the amount of dissolved calcium and magnesium in the water. The harder the water, the higher it is in dissolved minerals[2].

  • Soft water = less than 60 mg/L
  • Moderately hard = 61-120 mg/L
  • Hard = 121-180 mg/L
  • Very Hard = 180+ mg/L

So how often should you flush your water heater? About once a year in areas where the water hardness falls within normal ranges. If your water is hard or very hard, you might want to consider flushing the system two or more times per year.

Do I Need to Drain My Water Heater if I Have a Water Softener?

While you won’t need to drain as frequently as you would if you had hard water, you should still drain your unit regularly if you have a water softener. Even soft water has trace amounts of calcium and magnesium. When heated, these can leave deposits on the inside of your unit, putting you at risk of clogs and inefficiency.

The Drain Valve: How Water Heaters Are Flushed

Repairing and preventing clogs in your water heater requires flushing, and flushing requires the use of a working water heater drain valve. These can be either brass or plastic (brass lasts longer) and are usually located near the bottom of your water heater. The open end sticks out of your water heater. Water will drain out of that nozzle when the knob is loosened.

Flushing a Hot Water Heater: Gas vs. Electric

Starting the draining process is really what differs when it comes to gas versus electric units. For gas water heaters, you’re going to want to turn the gas valve to the off position. For electric water heaters, locate your circuit breaker and turn off the power. Once you have the gas or electricity off, you can turn off the cold water intake valve. If you’re going to be draining, you don’t want any new water entering the tank.

The Draining Process

Once you have your gas or electricity shut down, and your intake valve turned off, you’re going to want to let your water cool. Most water heaters are set to 120-140 degrees (the Environmental Protection Agency recommends 120 while the Occupational Safety and Health Administration recommends 140). Unless you want to handle 140 degree water (you don’t – most adults suffer third-degree burns if exposed to water this hot, even just for seconds).

Once cooled, follow these steps:

  • Connect a hose to the drain valve so you can control where the drained water goes.
  • Set the hose inside a bucket or next to a drain.
  • Go to a sink or tub inside your house and open a hot water faucet.
  • Turn the small slot on your drain valve to open.
  • Pull the tab to open the pressure relief valve.
  • The water will now begin to drain. Let this happen until no more water is emitted from the hose.
  • Flush out any sediment that might still be in your water heater by turning on the cold water valve.
  • When your water starts running clear, you’ve successfully cleaned out your unit!
  • Close the drain valve back up. Cold water will continue to fill the tank.
  • Once your tank is filled, you can turn the gas or electricity back on.

Added tips:

  • Wear rubber gloves, just in case the water is still too warm by the time you start the draining process.
  • Wear grungy clothes, just in case dirty water is spilled.

How Long Does it Take to Drain the Water Heater?

Aside from labor time, the tank size itself is what dictates how long it takes to drain your water heater. If you have a 50 gallon tank and the pressure of your hose allows the water to flow at 10 gallons per minute (GPM), then you can expect the tank to fully drain in about 5 minutes[3]. This is a relatively quick process, usually taking less than 10 minutes, but time can vary depending on how familiar you are with the process and your unit.

How Draining Your Water Heater Could Save You Money

According to the U.S. Department of Energy, water heaters that are running efficiently use less water and overall save you money on your utility bills[4]. Some people switch to more energy efficient units, but even cleaning your existing water heater can lower your energy bills.

Other ways your water heater could save you money:

  • Switching to a tankless water heater
  • Fixing leaks in your drain valve
  • Lowering the temperature setting (for every 10ºF reduction in temperature, you can save from 3%–5% on your water heating costs)

Emptying Your Water Heater: Tank vs. Tankless

If you own a tankless water heater and not a traditional tank water heater, the process for flushing your system will be a little bit different[5].

  • Start by turning off the power source.
  • Close off the water valve. There will probably be three attached to your tankless unit: one for cold water, one for hot water, and another for diverting water into your home.
  • Each of the cold and hot water valves will have a purge valve on them. Remove the caps on these valves.
  • You’ll need to attach a hose to each of the three valves on your tankless unit.
  • Twist the valves so that they’re perpendicular to the lines.
  • Rather than chemicals, many people recommend using white vinegar to clean the inside of the unit.
  • There should be manufacturer instructions to accompany your specific tankless water heater. Follow those to finish flushing and draining your system.

Why Use Vinegar for Water Heater Maintenance

Many people opt to use vinegar to clean their water heater instead of harsh chemicals since the water from that unit is what fills your sinks, faucets, bathtubs, etc[6]. If you opt to use vinegar, make sure it’s undiluted white vinegar. This cannot be interchanged for any other type of vinegar. To clean using vinegar, dump the vinegar into your unit and let it sit for a few hours. Next, drain it from the tank and refill it with clean water before turning the unit back on.

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