How to Drain Calcium from Hot Water Heater

  • While they are invisible to a passer-by, calcium deposits in a hot water heater can be deadly for your gas or electric heating device. 
  • Both gas and electric water heaters form mineral deposits around their heating elements. It’s typical for calcium carbonate to collect on the exterior of an anode rod in a water heater. It makes the hot water heaters work extra hard and may even burn out and shorten your heating devices’ lifespan.
  • Keep reading to find out how to ensure hot water heaters remain free of calcium deposits. Discover also how to remove calcium deposits if a sediment build-up appears.

Where does mineral buildup come from?

According to Rooter Guard, calcium deposits appear in a hot water heater system because of a mineral found in water called calcium carbonate. 

You’ll find these mineral deposits at the bottom of the tank when they start to precipitate out.

The water heater itself cannot control the sediment build-up problem. 

The dip tube, the cold water inlet pipe, is usually straight—when the water strikes the water heater ‘s bottom, it makes the sediment settle uniformly. 

In the water heater with a self-cleaning system, you’ll find a curved dip pipe in the tank instead of a straight one. In this construction, the dip pipe is equipped with a fitting designed to swirl the water around instead of simply dispensing it to the bottom. Swirling the water keeps the sediment moving and partly helps avoid a lime buildup problem. 

Why would these mineral deposits be a problem anyway?

An actual mineral deposits problem is the formation of the insulating layer in the middle of the water and the gas burner. 

This sediment buildup typically slows heat transfer, thus causing overheating in the heater ‘s bottom.

This overheating, in turn, causes the steel to weaken, damaging the glass lining. 

No wonder with these problems, you can’t expect the lifespan of your water heater tank to be as long as desired. 

Important: It buries the lower element in electric water heaters, triggering it to burn out.

When water heaters ‘ bottoms are covered with sediment, it also lowers the tank’s ability of the tank to conserve energy.

Moreover, sediment buildup creates a suitable environment for corrosive anaerobic bacteria to grow.

If it wasn’t enough, such mineral buildup can also pass in the re-circulation lines, blocking the open check valves, and causing the electric pump to stick (and eventually burn out). 

This problem will often clog the drain valve, hindering the flow of water and causing the water heater tank to produce loud and annoying noise.

How to remove calcium deposits?

Now the question is what to do when such sediment appears or, even better, how to protect your water heater from it.


Regular maintenance is indispensable. Waldman Plumbing suggests following these three steps to prevent scale buildup in your hot water heater.

  1. Flush the water heater regularly 

Flushing the water in the heater will also flush sediment that’s inside.

Do it with the frequency depending on the water type:

  • twice per year if you have hard water, or 
  • once annually if your water isn’t particularly hard;

Flushing the water heater takes around 20-60 minutes.

Important: Be careful! The water flowing from the heater will probably be very hot. Follow the instructions cautiously to avoid the risk of physical harm. 

  1. Add vinegar to the tank

After you have finished draining your water heater, fill it with a gallon of cider vinegar to the tank and let it sit for several hours—at least six. 

Cider vinegar is a mild acid, so don’t worry that it will damage the water heater. But, on the other hand, it’s powerful enough to dissolve lime buildup within the tank. 

After a few hours, open the drain valve and let water flow to flush the tank again, getting rid of vinegar and calcium buildup remaining inside. 

  1. Routine maintenance and regular inspection

Service your water heater annually or even twice a year. 

It will prevent scale buildup and prolong your heater ‘s lifespan.


The most effective method to ensure your water runs clear is to stop calcium before it has a chance to take over your water heater tank.

Yet, if this has already happened, here is what else you can do. 

  1. Install a water softener

This solution is designed to stop the buildup before it starts. As a result, it saves you time and money in the long run.

  1. Reduce thermal stratification

Consider using innovative tools such as The Bradford White Hydrojet Total Performance System. 

It’s a cold water supply pipe that reduces sediment buildup. It mixes incoming water thoroughly with stored water to reduce thermal stratification.

  1. Effective chemicals

Mind that striving for chemicals to be effective is not synonymous with choosing a commercial lime cleaner. 

You can treat your heater with organic products. Actually, the most effective chemicals for combating calcium buildup are vinegar or lye.

After flushing your water heater, let the chemicals sit in the tank for a few hours and flush it again before turning the heater on.

  1. Avoid high temperatures

The sad truth for those who adore hot baths is that the hotter the water, the more calcium it’s leaving behind. 

So make sure your water heater isn’t set above the manufacturer’s recommended temperature. It’s usually between 120ºF and 140ºF.

  1. Try a commercial lime cleaner

You can use, for example, CLR cleaner. Its name stands for calcium, lime, and rust, i.e., three substances that appear over time on surfaces that come into contact with water. 

CLR cleaner eats away all the minerals at the bottom of the heater without scrubbing. It comes in small spray bottles or gallon-sized containers. 

First, turn off the water heater and disconnect it from the cold water inlet pipe to use it. Then, attach a hose to the drain valve.

Keep the hose as straight as possible and put the other end of the hose over a basin. 

Important: Be careful as hot water will come out from there in a moment!

Now, you can open the drain valve and unscrew the pipe supplying water to the heater. The water will drain out of the heater and into the basin. Close the drain valve when it’s finished.

Pour a gallon of CLR into the inlet pipe. You can also use a gallon of vinegar, acidic tub, tile cleaner, or another commercial lime cleaner. 

Pour in one cup at a time, pausing after each cup (to prevent gas build-up), into the cold water inlet pipe. 

Wait five hours for your chemical product to dissolve the mineral deposits. Then, pinch the open end of a plastic bag over the inlet pipe and observe if it slowly inflates. If it does, wait another hour and test it again. When it stops inflating, the problem has been neutralized.

Connect the heater back to the inlet pipe and open the valve. Allow the water to run through for several minutes to rinse it.

Close the drain valve and turn on a hot water faucet to fill the water heater. Soapy water will begin to flow from the faucet. Continue until the water flowing from the faucet is free of bubbles.

Open the rest of the hot water faucets in the building—the goal is to replace the air in the pipes with water. Then, turn on the hot water heater and see if the water runs clear.

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Frequently Asked Questions

To deal with lime buildup, you'll need to learn that it's inside the tank. So, what are the symptoms? If you can't arrive at hot water temperature, it takes a long time to heat, or its temperature fluctuates, there may be a problem. Also, if hot water coming from the tank looks rusty and smells foul, there are small leaks near the water heater drain valve, or you can hear popping or rumbling noises coming from the tank.
Hard water means there are excess minerals in the water supply. Such water contains a lot of calcium, leading to a limescale buildup. Drinking such water is relatively harmless for people, but it can cause massive damage to your household appliances—especially the water heater.
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