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Annual Tankless Water Heater Maintenance Requirements

Jennifer Hansen
Last Updated on
by Jennifer Hansen

Tankless water heater maintenance is a must and should be done at least once a year. Also commonly referred to as an on-demand water heater, the tankless water heater may need maintenance every six months if your water heater is set to a high temperature or if you have hard water

The On-Demand Water Tank 

Tankless models don’t come equipped with a large storage tank. Instead, on-demand water heaters heat water directly as it flows through the cold water line. So, when you use hot water, you’re basically activating the water heater. 

An on-demand water heater utilizes heating elements, also known as heat exchangers. 

Maintenance Needs

How long do water heaters last? These water heaters can last over twenty years, but that’s with regular maintenance. Because most manufacturers often market these water tanks as no maintenance or low maintenance, most people fail to properly maintain them, which can have a major impact on the water heater’s longevity. 

So, if a tankless water heater doesn’t have a storage tank to clean, what type of maintenance do they need? 

In terms of maintenance needs, there really isn’t much of a difference between maintenance care for tankless and traditional water heaters. 

But why?

The answer is simple: hard water will affect both tankless and traditional models. 

Need Help With Maintenance?

No problem, Get free estimates online from trusted Water Heater Experts near you.

What is Hard Water?

Hard water simply means that the water in your area is loaded with minerals, mainly magnesium and calcium. With on-demand water heaters, minerals will build up inside the heat exchanger. Over a period of months, minerals will plug up the passages where the water flows, significantly affect water flow speed. This forces the water heater to work harder than it should in order to deliver hot water. 

If you fail to clean out the heat exchanger, over time, this can shorten the water heater’s lifespan and can even cause your energy bill to skyrocket. Additionally, this type of mineral buildup on the heat exchanger can cause irreversible damage. In severe cases, the heat exchanger or the entire unit will need to be replaced. 

Unfortunately, most manufacturers do not cover this type of damage under the warranty. 

Does My Tankless Water Heater Need Routine Maintenance?

Even higher priced, top of the line tankless water heaters such as the Rinnai RUC98iN Ultra Series require ongoing maintenance. To learn more, read the user’s manual and check out the recommended frequency and specific maintenance needs. 

If you’d like to learn more about leading models of on-demand water heaters and how they work,  read our tankless water heater buyer’s guide.

Need Help With Maintenance?

No problem, Get free estimates online from trusted Water Heater Experts near you.

Pro Maintenance Needs

Pro Maintenance Needs

We recommend having the water heater professionally serviced. During a routine maintenance visit, a pro will delime or descale the water heater in order to remove any mineral buildup around the heating elements. 

The water heater should be descaled at least once a year, but as we mentioned, if you live in an area that has hard water or if you normally keep the water heater’s temperature set high, then you’ll need to have the water heater serviced once every six months. 

Regardless of where you live, the water that enters the heater will carry with it some amount of minerals. However, in certain parts of the country, the water is much harder, which means it has a higher than normal mineral content. 

If you live in a part of the country that has hard water, you’ll need to have it descaled more often in order to protect the heating elements. 

Now, if the water heater’s temperature is set too high, then you’re also at an increased risk for scale buildup. Many chemicals dissolve much faster once heat is applied. This means, the hotter the water is, the faster minerals will build up around the heating elements. 

Need Help With Maintenance?

No problem, Get free estimates online from trusted Water Heater Experts near you.

Is Your Water Heater Set Too High? 

If you’re not sure if your water heater is set too high, check it with a thermometer to see what temperature it’s set at. If the temperature is higher than one hundred and twenty degrees, then it’s probably time for routine maintenance. 

Do it Yourself Maintenance 

If you prefer doing the routine maintenance yourself, make sure you read the included user’s manual for maintenance care instructions. 

To start, switch off the tank’s power. Remove the tank’s lid. This usually involves unscrewing three to four screws. 

Make sure you have closed off the water valves that supply the water heater. 

Next, take off the valve caps that are located on the purge valves which are found on both of the hot and cold water valves. This will relieve any built-up pressure inside of the valves and can also prevent any excess water from shooting out and scalding your skin. 

The next step involves attaching the hose lines to each of the valves. The manufacturer usually includes these with the water heater. 

Now you’re ready to open the purge port valves. They should be twisted perpendicularly to the position of the hot and cold valves. 

Use three gallons of white vinegar in order to clean out the heater and instantly remove any built-up mineral deposits around the heat exchangers. 

Next, drain and flush, using the directions provided by the manufacturer. 

You can now twist the T shaped handles to close the purge port valves after you’ve finished flushing out the water heater. 

Disconnect each hose line and replace the caps on the purge port valves. Be sure to tighten each cap properly. 

Locate the filter and remove it by unscrewing it. Clean the inside screen and the housing of the filter by rinsing it off. Once complete, replace it. 

In order to safely restart the water heater, refer to the manufacturer’s instruction manual. 

And that’s it. This job seems simple enough, but if you fail to follow the manufacturer’s maintenance instructions you can end up damaging the heating elements. If you don’t have the instructions you can contact customer support or visit the manufacturer’s website.

Need Help With Maintenance?

No problem, Get free estimates online from trusted Water Heater Experts near you.

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About Jennifer Hansen
Jennifer Hansen
Jennifer is a clean water enthusiast and the lead editor of Water Filter Spot and created this website several years ago to share information that she's been researching in this industry for over 20 years. Jennifer studied environmental resource science in college and studied Western US water issues, including water policy, water rights, water pollution and environmental concerns.
Jennifer Hansen
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