Do tankless water heaters need to be flushed annually?

Author: Alfonzo Considine  |  Last update: Sunday, April 20, 2025

Over time, a tankless water heater may accumulate mineral build up which can erode the walls inside your tank's heating chamber. To properly maintain and clean your tankless water heater, it's important to flush those mineral deposits at least once a year.

What happens if you don't flush a tankless water heater?

What happens if I don't flush out my tankless water heater? Mineral deposits may build up. This could cause a clog within the unit and may prevent normal heating activity. Your hot water could also fluctuate and overheat the system, impacting its efficiency.

How often should I flush tankless water heaters?

Just like a tank unit, tankless water heaters need to be flushed once per year. Homeowners with hard water should consider flushing and cleaning the unit even more frequently, perhaps every six to nine months because of the excess amounts of magnesium and calcium found in hard water supplies.

How do I know if my tankless water heater needs to be flushed?

Common signs it's time to flush or drain your water heater include:
  1. Low water pressure.
  2. Water takes a long time to heat up.
  3. Water isn't the correct temperature or fluctuates.
  4. Noises coming from the tank, such as rumbling or popping.
  5. Sludge or discolored water.
  6. Frequent Repairs.

What is the average cost to flush a tankless water heater?

The average cost to flush a tankless water heater can vary. On average, homeowners can expect to spend between $100 and $300 for a professional flush, including any additional maintenance services required. DIY flushing costs can range from $30 to $100, depending on the flushing kit purchased.

3 Things They Don’t Tell You About Tankless

Can I flush my own tankless water heater?

With the right tools and knowledge, you can certainly flush a tankless water heater by yourself. In fact, there are water heater flushing kits you can buy online for the job, which come with everything you need. They include things like a circulation pump, hoses, a bucket and a cleaning agent.

How much does your electric bill go up with a tankless water heater?

How Much Electricity Does a Tankless Water Heater Use? Many people wonder if tankless water heaters increase electric bills. The answer is no — tankless water heaters can save money on your monthly electric bill because they're 8%-34% more efficient than storage water heaters.

What maintenance do tankless water heaters require?

To maximize your tankless water heater's performance and service life, it's important to regularly clean or replace the water filter, clean the air filter (for gas units), and descale and flush the system.

Should you flush a water heater that has never been flushed?

(Don't worry! It doesn't come out of your faucets.) If neither you nor a professional have flushed your water within the last five years, Water Heaters Now recommends not flushing it yourself.

How long does a tankless water heater last?

One of the most common questions asked by consumers about tankless water heaters is how long they will last. A tankless water heater can last anywhere from 15 to 20 years with proper maintenance and operation. In comparison, a standard tank water heater normally has a working life of 10 years or less.

How long does it take a plumber to flush a tankless water heater?

Tankless water heaters are efficient and effective, but they require maintenance to ensure they do not build up scale. Flushing your tankless heater is a simple task, but it does take 1-2 hours to complete.

How much for a plumber to flush a water heater?

Your average water heater flush cost falls around $160, with most prices ranging from $110 to $200 depending on several factors.

What is the best chemical to flush a tankless water heater?

Use 4 gallons (15.1 liters) of undiluted white vinegar to clean your tankless water heater. Never use chemical solutions of any kind. Since your home's drinking and bathing water mostly likely flows through your tankless water heater, using chemical cleaning solutions could be extremely harmful to your health.

How much does it cost to service a tankless water heater?

The most common expenses associated with tankless water heater maintenance are labor costs, replacement parts, and annual or semi-annual maintenance checks. Labor costs can range from $50 to $150 per hour, while replacement parts can cost between $20 to $500, depending on the part's complexity and brand.

Do you ever run out of hot water with a tankless water heater?

You can't run out of hot water with tankless water heaters – unless, of course, the power supply is off or goes out. However, a tankless water heater can have trouble keeping up with demand if too many things require hot water all at once.

How often should I clean out a tankless water heater?

Most manufacturers recommend descaling your system once per year. For homes with hard water, equipment may require more maintenance. However, you should always check the manufacturer's instructions specific to your equipment to ensure the safest and most effective maintenance schedule.

Do I really need to flush my tankless water heater?

Many people ask us if they still need to flush their water heater after switching to tankless, and the short answer is yes. Even though there is no tank for water to sit in, sediment can still build up inside the unit and most manufacturers require an annual flush in order to keep the warranty valid.

How do I know if my water heater needs to be flushed?

Keep an eye out for debris suddenly showing up in your water. If you notice sediment or any brown sludge coming out of your faucet, that's probably an indication that it's time for a water heater flush. If you see any of these signs, it's a good indication that your water heater needs maintenance.

Should I flush my water heater every year?

But, you can help yours get to the top of that lifespan range by: — Flushing and draining your water heater at least annually, if not 2-3 times per-year.

What happens if you don't service your tankless water heater?

If you neglect maintenance on your tankless heater, it will reduce the lifespan of your investment. You could go years without performing maintenance and the heater will still function. It won't heat the water efficiently, but it will still produce hot water at a reduced flow rate.

How often do you change the filter in a tankless water heater?

To keep your tankless water heater in prime condition, it is advised to clean out the filter once every six months. This routine maintenance is easy to do and only takes a few minutes. Simply watch our how-to video above or continue reading to learn how to clean your tankless water heater filter.

What is the best tankless water heater?

7 Best Tankless Water Heaters for Large Homes in 2025
  • Best Overall: Rinnai RU199iN.
  • Best Premium: Navien NPE-240A.
  • Best Gas Option: Rheem RTGH-95DVLN.
  • Best Electric: Stiebel Eltron Tempra 36.
  • Best Value: EcoSmart ECO 36.
  • Best Compact: Takagi T-H3-DV-N.
  • Best Warranty: Noritz NR981-DVC-NG.

What is the downside of a tankless water heater?

Before you commit to buying a tankless water heater, the primary drawbacks to know include: Higher upfront costs. Tankless water heaters are, on average, quite a bit more expensive to buy and install than tank water heaters. Access to fuel.

Why is tankless water heater installation so expensive?

Installing a tankless water heater can require gas line upgrades, electrical modifications, and specialized venting—all of which can increase costs. Professional labor also runs from $500–$1,500 due to complex installation requirements.

Do you really save money with a tankless water heater?

Electric tankless water heaters still save homeowners around $44 per year according to the US Department of Energy. Longer useful lives than storage tank water heaters. Tankless water heaters typically last 20 to 30 years, double the forecasted useful life of a storage tank water heater.

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