How To Flush Your Tankless Water Heater

About Me
Minimizing the Need for Plumbing Repairs

Hiring a plumber to make repairs tends to be a common occurrence for most homeowners as the years pass. While it’s virtually impossible to completely avoid the need for a professional plumber’s services, there are some things you can do to minimize wear and tear on your plumbing system so it doesn’t succumb to the need for repairs often. Using low-flow aerators on your sink faucets and shower heads as well as insulating your exposed pipes before winter can make a big difference in your plumbing’s performance. On this website you’ll find many tips and tricks that can be used to keep your plumbing in good shape, and even to save yourself some money on water costs throughout the year.

How To Flush Your Tankless Water Heater

20 May 2016
 Categories: , Articles


If you have a tankless water heater, then you will need to worry about minerals depositing within the system, much like happens with a tank model. In fact, you may need to worry about the issue even more. Keep reading to learn why this is an issue and what can be done to remove solidified minerals within the heater.

How Do Mineral Accumulate In The Appliance?

If you have extremely hard water, then you probably notice scale build up around your home. This scale is made up of calcium and magnesium deposits. When water is heated, these minerals leach out of the water and attach themselves to pots, shower heads, washing machine basins, and dishwasher sprayers. The minerals also deposit inside water heaters. This issue is extremely common with tank heaters, because heated water will sit for some time. This allows more of the minerals to deposit and accumulate before water flows out of the tank. However, issues can occur in tankless water heaters too.

Tankless water heaters use heat exchangers to heat water as it moves through the appliance. Water will move through a coiled copper pipe. The heat exchange element or flame will sit below the coiled pipe. Heat rises from the element and heats the water flowing through the coil. As the water is heated, some mineral deposits will build on the inside of the coil. As this happens, water will not be able to flow as easily through the pipe. Also, you may notice that water is not as hot. While copper is a great conductor of heat, mineral deposits will prevent heat transfer from the copper to the water. 

How Can Minerals Be Removed?

Minerals can be removed from the water heater by flushing the system. Vinegar can dissolve minerals fairly easily, so it is best to use vinegar to complete the flushing. You will need to start the process by shutting down the system. Flip the breaker that provides electricity to the unit and close the cold water supply valve and the hot water valve as well. If the unit uses gas, then you will need to shut off the gas to the unit too. 

Most tankless water heaters will have isolation valves attached to the cold water inlet and hot water exit pipes. These valves allow you to access the piping of the unit while also cutting off the flow water. These valves will have a separate and open connection on the side where a garden hose can be connected. You will need to connect a garden hose to the cold and hot water isolation valves. Once the hoses are connected, you will also need to connect a portable sump pump, pond pump, or small aquarium pump to the other end of the hot water valve hose. If you do not have an appropriate pump, then consider purchasing a pump made to fill and remove water from water beds. These pumps, along with portable utility pumps, are relatively inexpensive and easy to use. They typically come with garden hose attachments already connected as well.

You will need to gather two five gallon buckets. Fill one bucket with about two gallons of vinegar and two gallons of water. Place the end of the cold water connected hose in the bucket. Place the pump in the other empty bucket. If the pump is not a submersible variety, then you should place the pump in a sink, near a drain, or next to your sump pit. This will allow the vinegar water to drain away from the pump. 

Once everything is set up, turn on the pump. The vinegar water will move through the pipes of the water heater and flush out the mineral deposits. Remove the hoses when you are finished, turn the water valves back on, and turn on the electricity. Run hot water in your kitchen or bathroom sink. If water flow is more consistent and hotter, then the flushing process was a success. 

If it doesn't seem to work, it may be time to contact a water heater repair company to help you solve the issue and get your water heater working efficiently again.