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

Author: Cristina Conn  |  Last update: Thursday, December 18, 2025

In standard tank models, failing to descale can pose a risk of explosion. Tankless water heaters won't explode, but if you don't flush out the sediment, you may force the unit's heat exchanger to work harder than necessary.

Do tankless water heaters need descaling?

Note: It's good practice to mark when you last descaled your water heater. Depending on your water hardness and usage, it's recommended that you descale your tankless water heater every 6 to 12 months.

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 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 much does a plumber charge to descale a tankless water heater?

Flushing and descaling are important parts of that maintenance, no matter what kind of water you have. Descaling your tankless water costs between $150 and $450 on average.

3 Things They Don’t Tell You About Tankless

Does vinegar work as well as descaling solution for tankless water heater?

Both vinegar and descaling solution work well for cleaning mineral deposits, calcium, and limescale from your tankless water heater.

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 happens if I don't descale a tankless water heater?

In standard tank models, failing to descale can pose a risk of explosion. Tankless water heaters won't explode, but if you don't flush out the sediment, you may force the unit's heat exchanger to work harder than necessary.

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 many years 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.

Who descales tankless water heaters?

Plumbing professionals will be able to descale, along with performing any other required tankless water heater maintenance or service. Professionals have all the tools, test equipment, and experience to perform service in less time than most end users.

How much should it 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.

What maintenance is required for a tankless water heater?

The most complicated and time-consuming tankless water heater maintenance is typically descaling and flushing out the unit. Even with the inline water filter, lime and calcium deposits can build up inside the tankless system. If you have hard water, it's a good idea to descale and flush the unit once a year.

What happens if tankless water heater is not flushed?

You need to flush a tankless water heater once a year to get rid of mineral deposits and sediment that block the water flow. If you don't, this problem can cause your tankless hot water heater to stop working. You also might void the warranty by not doing it.

Can you run vinegar through 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.

Why does my tankless water heater turn blue when I flush with vinegar?

The vinegar will be a bit blue. This is from tiny amounts of corrosion of the copper of the tubes in heater. The copper imparts the blue color. Nothing to worry about.

What is the best solution to descale a tankless water heater?

Tankless water heater descalers are specifically formulated to effectively remove scale buildup without causing damage to the water heater components. However, if you prefer a natural and cost-effective solution, vinegar can be used as an alternative.

How much does a plumber charge to flush a water heater?

The national average cost to flush a water heater is $160, but prices can vary in increments based on the tank size. A 30-gallon tank will cost between $90 and $120 on average, while a 70-gallon tank could cost anywhere between $180 and $250.

Can you burn out a tankless water heater?

If a heating element begins to ground out, it will stay on all the time and overheat drastically. Not surprisingly, the result will be painfully hot water – and that's just for starters. With time, the heater element will burn itself out completely. Then you'll have no hot water at all until the element is replaced.

How long does it take to descale a tankless water heater?

Step 7: Allow the pump to circulate the Haymaker solution through the water heater for 30 to 45 minutes. This will help break down any mineral deposits or sediment that may have built up over time. Step 8: After at least 30 minutes, unplug the pump, close the service valves, and dispose of the solution.

Can you clean a tankless water heater yourself?

Flushing a tankless water heater is a bit different from flushing a traditional system. Here's a key difference: unlike draining and flushing a traditional water heater—which almost any homeowner can do with just a few basic tools—you'll typically need some specialized equipment to clean out your tankless system.

Is there any reason not to get a tankless water heater?

Additional Installation Costs

As a result, they require professional installation. If you're switching from a hot water tank to a tankless unit, you will likely need your gas lines rerouted, as well as a larger gas supply line. Both of these alterations will increase the cost of installation.

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.

What is the life expectancy of a tankless water heater?

Tankless water heaters usually last for around 15-20 years before they need to be replaced, but they may need replacing sooner if they start to break down or lose efficiency. Some common signs your tankless water heater needs to be replaced include: Low water pressure. Water doesn't get hot.

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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