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

Author: Asha Bode DVM  |  Last update: Wednesday, December 17, 2025

Flushing your tankless heater is a simple task, but it does take 1-2 hours to complete. For most water quality, completing this task once a year will suffice, but if you have especially hard water you may want to complete more often.

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.

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

On average, this process will take anywhere from an hour to two hours to complete, so make sure you leave yourself enough time to let the cleaning process run its course. When time's up, stop the pump and close off the valves.

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

Shortened Lifespan: A water heater that isn't flushed regularly may experience corrosion and other damage more quickly, leading to a shorter overall lifespan. Water Quality Issues: Sediment can affect the taste and quality of the water, potentially leading to discolored or foul-smelling water.

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.

How To Flush A Tankless Water Heater The Easy Way | DIY Plumbing

How many gallons of vinegar do I need to flush my 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 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.

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

After resetting your tankless water heater, you may be wondering how long it will take for the water to heat up again. The heating time depends on the size of the tankless water heater. In general, gas water heaters can heat water within 30-40 minutes, while electric tankless water heaters may take about 60-90 minutes.

What happens if you never flush your water heater?

-Reduced Efficiency: As scaling collects at the bottom of the tank, your water heater will become less effective at heating the water in the tank. -Corrosion: If your water heater goes long enough without a proper flush, you could also have corrosion attacking the tank itself, weakening its structural integrity.

Is it OK to unplug a tankless water heater?

There are no renowned damages that come with turning off the heat supply for your tankless water heater. Turning off your water heater and the main water supply is best for you when you are going for a break.

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 clean your own tankless water heater?

Connect a small sump pump to the hose and submerge the pump into a five-gallon bucket (or larger) filled with three gallons of distilled white vinegar. Run the sump pump for one hour. This will flush the vinegar through the system, where it will break down limescale and mineral buildup.

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

Installing a tankless water heater typically takes four to five hours, depending on the type of system and a household's needs. The installation process duration also depends on your location and which professionals are available when you need an installation.

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.

Can I flush my water heater myself?

You can flush your water heater yourself if it's done on a regular basis. This guide will take you through the steps to drain and flush a gas or electric water heater. Learning how to clean a water heater is an essential part of maintaining your plumbing system.

Do tankless water heaters need to be flushed annually?

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.

Should I flush a 15 year old water heater?

If neither you nor a professional have flushed your water within the last five years, Water Heaters Now recommends not flushing it yourself.

Is it better to flush or drain your water heater?

It is recommended that you flush your water heater at least once per year. Doing so will help to prevent the potential problems that sediment can bring over time. Typically, it takes one to two hours to flush a water heater. The size of your tank will impact the amount of time it takes to drain.

How to tell if your hot water heater is full of sediment?

Common signs that sediment buildup is significant include bubbling and gurgling sounds and diminished hot water when bathing, cooking, or cleaning. You may also notice water discoloration, a leaking pressure relief valve, or cracks in the tank or its connections.

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.

Why is my tankless water heater so cold after a few minutes?

One common cause of a drop in water pressure and a loss of heating in a tankless water heater is a clogged water filter. The water filter is responsible for keeping sediments and dirt out of the unit, but over time, it can become clogged and restrict the water flow.

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

Flushing your tankless heater is a simple task, but it does take 1-2 hours to complete. For most water quality, completing this task once a year will suffice, but if you have especially hard water you may want to complete more often.

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 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.

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.

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