How often does a tankless water heater need to be flushed?

Author: Alejandrin Blick  |  Last update: Monday, February 23, 2026

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.

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.

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 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.

Can I flush my own tankless water heater?

A tank heater is very easy to flush, you just need a garden hose, drain it fill and check anode rod. A tankless is also easy to flush, you will also need a pump and a bucket.

How To Flush a Tankless Water Heater in 3 Minutes

What maintenance is required for tankless water heaters?

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.

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.

How long does a tankless flush take?

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.

Do tankless water heaters get clogged?

If you don't flush out a tankless water heater, minerals and sediment will build upon the filter and in the hose. That will affect the water flow: One that's clogged, you won't get hot water.

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 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.

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.

Do plumbers recommend tankless water heaters?

Tankless Water Heaters: Tankless water heaters, also known as on-demand or instantaneous water heaters, heat water directly without the need for a storage tank. Plumbers recommend tankless water heaters for their energy efficiency, space-saving design, and endless hot water supply.

Should I flush my water heater after 7 years?

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

Do you ever run out of hot water with tankless?

If you turn on the shower for hot water, the tankless system will detect the movement of water in the hot water lines and start to apply heat through a heat exchanger to the water. It will keep doing this as long as there is demand – and that means you won't run out of hot water!

How often should I flush a tankless water heater with a water softener?

If you have hard water, it is important to descale and flush your unit at least once a year. If you have a water softening system, we recommend performing a flush of the system every 3-5 years.

What happens if tankless water heater is not flushed?

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.

Why don t more people use tankless water heaters?

Some people hesitate to decide on a tankless water heater because they can be a slightly higher cost; however, you get significantly more life out of one. A standard water heater tank lasts about 8-12 years. A tankless water heater can last as long as 25 years!

How long do you run vinegar through a tankless hot water heater?

Flushing Your Tankless Water Heater
  1. To begin flushing, open the hot- and cold-water ports, turn the pump on, and allow the vinegar to circulate for about an hour. ...
  2. Dump the vinegar from the bucket and close the cold-water service port.
  3. Remove the hose and open the cold water shut-off valve to flush any remaining vinegar.

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

Key Takeaways: Tankless water heater flush cost can range from $50 to $1,300, with an average cost of around $600. The maintenance cost is influenced by factors such as the size of the water heater, materials needing replacement, labor costs, and location.

How often should a tankless water heater be serviced?

However, these systems require proper maintenance to prevent premature component failure and ensure long service life. Generally, tankless water heaters should be serviced once a year; however, they may require more frequent maintenance if you have hard water or if you keep your water temperature high.

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 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.

How often should I replace my anode rod?

Anode rods require routine inspection and replacement, approximately every three to five years. Without proper maintenance, the anode rod loses its ability to divert damaging particulates from your tank and can accelerate rust and corrosion from chemical reactions, excessive heat, and imbalanced pH levels.

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.

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