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How Often Should You Flush Your Water Heater? – Detailed Guide

Fact checked by Stephen Conklin

how often should you flush your water heater

Are you anxious about keeping your water heater in tip-top condition, maybe afraid sediments will accumulate at the tank’s bottom? Do you often find yourself asking the question, how often should you flush your water heater?

Flushing the hot water tank is crucial in maintaining the water heater’s optimal function. It allows families to enjoy hot water for many years without worrying about costly repairs due to water heater dysfunction.

Knowing the frequency of water heater flushing should help you maintain your appliance’s integrity.

Table of Contents

How Frequently Should You Flush a Water Heater?

There are no clear guidelines on how often you should flush a water heater. Some experts recommend flushing the hot water tank at least once annually, while others advise doing so every four to six months.

Despite the differing views, experts agree that all water heaters must undergo regular flushing. The activity is crucial to remove sediments and mineral deposits from the water heater’s interior chambers. Failure to flush hot water heater periodically can undermine the appliance’s full functionality.

What Factors Can Impact Water Heater Flushing Frequency?


A few factors can affect the frequency of flushing water heaters.

The first factor is water hardness level. The US Geological Survey defines water hardness relative to calcium carbonate levels in the water. The agency categorizes hard water levels into four, as follows.

  • Soft water – up to 60 calcium carbonate parts per million (ppm) or 0-60 milligrams per liter (mg/L) or less than 3.5 grains per gallon (GPG)
  • Moderately hard water – 61 to 120 ppm or 61-120 mg/L or 3.56 to 7.0 GPG
  • Hard water – 121 to 180 mg/L or 121-180 ppm or 7.1 to 10.5 GPG
  • Very hard water – more than 10.5 GPG or over 180 mg/L

While calcium carbonate does not cause human health problems, it can produce limescale that adheres to the interior surfaces of plumbing systems, including water heaters.

Unchecked limescale buildup in water heaters can impact the appliance’s functionality. It can reduce the efficiency of heating elements and make it challenging for gas-powered water heaters to maintain optimal water temperatures.

Limescale can make the water heater work double-time, hasten wear, and reduce the appliance’s lifespan. Your water heater might last only eight years or less instead of the typical 10 to 15 years.

Flushing the water heater regularly can prevent calcium carbonate buildup by washing away calcium deposits.

Answering the question, how often should I flush my water heater depends on your house’s hard water levels. The higher the calcium carbonate levels, the more frequent is the flushing process. If you have hard water, doing it once every three to four months should be ideal.

The second factor is the sediment levels in the water. Solid particles can also adhere to the heating element and prevent heating the water to the ideal temperature. In such situations, you will not have hot water in your home.

Flushing the water heater removes these sediments and washes them away down the drain. It also replenishes the water heater with fresh, clean water.

What Is the Difference Between Flushing and Draining a Water Heater?


Some people confuse flushing with draining, and they also ask, how often should I drain my water heater?

While draining and flushing a water heater can have the same goal, they differ in the water source status.

When you drain your hot water tank, you empty its contents by closing the valve that regulates water flow to the water heater. You can then drain the water in the tank by opening a nearby faucet and the drain valve at the hot water tank’s bottom section.

Draining the tank allows you to spray the interior with water as you would when cleaning the insides of a water container. However, water heater manufacturers advise against using high-pressure water jets because it might damage the heating elements and other water heater components.

One must also not use harsh chemicals in cleaning the water heater’s interior, unless the manufacturer recommends a specific cleaner. In general, people can use apple cider vinegar to wash and clean the water heater’s interior.

On the other hand, flushing needs a continuous water flow, requiring the cold water shutoff valve to stay open while the water goes out through the drain valve. The constant water movement washes away sediments, hard mineral deposits, and other particles in the water.

The continuous water flow replaces the water in the tank with clean and fresh water.

Flushing can be done any time you have stale water while draining should happen several times annually.

Is It Necessary to Drain and Flush a Tankless Water Heater, Too?

Regular hot water heater maintenance flush is not only applicable to tank systems. Periodic flushing is also ideal in tankless water heaters.

Although tankless water heaters do not have a tank where hard minerals can deposit, they have heat exchangers that could clog with debris, sediment, and limescale.

The heat exchanger transfers heat from a tankless water heater’s burner or heating element to the water. That is why you get hot water on demand. Unfortunately, the heat exchanger has tiny and narrow coils that sediments and other particles can easily block.

That is why it is essential to flush a tankless water heater at least once a year. It would be best to flush the tankless water heater more frequently if you have hard to very hard water. you’d better consider water softeners designed specifically for hard water, which will be more efficient and require less maintenance.

What Happens if I Do Not Flush My Water Heater?

Not flushing your water heater as frequently as possible undermines your water appliance’s efficiency. Hard mineral deposits will make your water heater work harder to maintain the ideal water temperature. Over time, the water heater can no longer heat the water to the preferred temperature.

Water heater inefficiency is not the only concern when you do not flush it regularly. Hard water can also contain iron molecules that corrode the tank. Rust can eat through the metal surface and prompt you to replace the hot water tank.

Failure to flush the water heater periodically can also block the temperature and pressure (T&P) relief valve. A clogged T&P valve can have serious safety implications. This component releases excess steam and pressure from the expanding hot water tank. Blocking it prevents the tank from venting extra pressure.


You now know how often should you flush your water heater. Ideally, you must drain and flush the water heater at least once every six months, more frequently if you have hard water and high sediment levels.

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