5 Best Tankless Water Heater Kits (Reviews and Buying Guide)

If you’ve noticed that a recent decrease in water from your tankless water heater, it could be a sign that the internal components of the unit are wearing out. Although you can’t see it, sediments, minerals and lime scale can easily build up in tankless water heaters, damaging the system and reducing their efficiency.

The best solution for this problem is to flush your tankless water heater at least once a year. You can get a professional to do this, or, if you’ve got the right equipment for it, you can do the job yourself. Purchasing a tankless water heater cleaning kit will allow you to clean the heater easily and effectively.

In this article, we’ve compiled a list of the top 5 tankless water heater flush kits on the market. The second section of the article will cover how to purchase and use one.

Tankless Water Heater Kits

Whitlam KITC System Descaler FLOW-KIT

8 new from $154.99
1 used from $127.96
as of October 26, 2023 12:52 am


  • NSF/ANSI 60 certified
  • Environmentally friendly
  • Safe for use
  • Connections may leak

The first product on our list is the KITC Flow-Kit from Whitlam. The complete kit includes a pump, rubber hoses, the descaling liquid and a bucket. The kit works effectively and quickly to dissolve water scale, rust, lime and other deposits that form in your tankless water heater.

Whitlam KITC is certified to meet NSF/ANSI 60 standards for use as a cleaner in potable water systems and is designed to work on any piece of equipment that’s water-based. Powerful, yet perfectly safe, the liquid is non-flammable, non-toxic, non-corrosive, biodegradable and non-hazardous. Its environmentally friendly and safe to use.

The kit is specially designed to work with tankless water heaters which provide ¾” cold or hot service connections. It comes with the complete set required for cleaning your water heater, including a 3.5 gallon bucket, 2 rubber hoses, 1 quart flow-aide and a 350 GPH pump.

What we didn’t like about this product is that the connections can leak unless they’re tightened and sealed. Some customers report that using channel lock pliers kept the system from leaking. Other than that, it’s a top-quality product.

ECOSMART – Tankless Water Heater Flushing Kit

2 new from $174.99
as of October 26, 2023 12:52 am


  • Connects easily to tankless isolation valves
  • Expensive
  • Compatible with all tankless water heaters
  • Easy to set up

The Ecosmart Tankless Water Heater Flushing Kit works brilliantly to clean your water heater system by eliminating buildup. It’s a non-hazardous and biodegradable descaler, which makes it safe to handle. The descaler contains heavy-duty agents that dissolve the buildup of limescale, rust and other deposits commonly found in tankless water heater systems.

This flushing kit comes compete with all required components. It includes a 32 oz bottle of Flow-Aide, hoses, bucket and floor sucker pump are included. Simply flush the water-heater system as often as is recommended by the manufacturer to eliminate debris buildup, improve the quality of your water and ensure optimal efficiency of the heater.

What we loved about this product is that it comes with detailed, step-by-step instructions which are clearly explained and easy to follow.  You can do it by yourself without needing to hire a professional plumber. As it comes with all the required parts, you don’t have to go out and purchase them separately.  

Hercules HAYMAKER Descaler Kit

8 new from $183.00
as of October 26, 2023 12:52 am


  • Safe for potable water systems
  • Non-corrosive
  • Solvent-free formula
  • Removes sulfates
  • Meets NSF Standard 60

The Hercules Haymaker Descaler is a citric based, non-corrosive solution that effectively removes lime deposits, rust and scale from your tankless water heater. Simply allow the product to circulate for about 10 minutes to clean out the buildup. The Hercules Haymaker also removes sulfates, unlike most other products on the market.  It comes with all the necessary components needed to set it up, including two hoses, a 550 GPH pump, one quart of cleaning solution and a 3.5 gallon bucket.

Made in the United States, this descaler kit meets the NSF standard 60 and is compatible with most metal, rubber, ABS, PVC and CPVC materials. When used regularly, it can extend the life of your water heating system but should be used as part of a regularly scheduled preventative maintenance program.

Kelaro Tankless Water Heater Flushing Kit with Rectorseal Calci-Free

as of October 26, 2023 12:52 am


  • Easy DIY installation
  • Descales in 30 minutes or less
  • Easily connects to tankless isolation valves
  • Affordable
  • No unpleasant odor

The Kelaro Tankless Water Heater Flushing Kit works quickly, taking 30 minutes or less to descale a tankless water heater.

This system is easy to install since all the components are included in the box along with a detailed instruction manual. The kit consists of a 1/8 HP utility pump, the manual, Calci-Free tankless water heater flush cleaner and a 3.5 gallon bucket. It also comes with 6 inch color coded rubber hoses that allow for easy and leak-proof connections.

The kit is compatible with all top tankless water heater brands, including Rheem, Rinnai, Bosch and Stiebel, to name just a few. What we liked best about the cleaner is its effectiveness, making short work of cleaning your heater without leaving behind a strong odor like some products tend to do.

Rheem RTG20124 Flush Kit

as of October 26, 2023 12:52 am


  • Bigger bucket – 5 gallon capacity
  • Plug and play mechanism
  • Easy to connect
  • For best results, use regularly

The Rheem RTG20124 Flush Kit is produced by one of the best-known manufacturers of tankless water heaters. It comes with a hefty pump that has the capacity to handle a heavy-duty workload with a cycle of 7 GPM. Although it’s not the fastest of pumps, it works great when compared with others, easily cleaning out the interior components of your tankless water heater.

This flush kit has an easy installation option which can save you a lot of time and includes a decent manual with clear instructions. One of the best features of this product is the 5-gallon bucket which has a bigger capacity than all the other kits on our list. It allows you to clean multiple heaters with one bucket of the solution, saving time as well as your effort.

The one downside of this flush kit is the quality of the rubber hose. While the rest of the accessories are quite of good quality, the hose isn’t quite durable which means that you’ll probably need to replace it sooner than expected. Apart from that, it’s an excellent product that’s made to satisfy.

What’s a Tankless Water Heater Flush Kit?

Tankless water heater buying guide

A tankless water heater flush kit allows you to flush your water heating system without having to pay for maintenance.

Over time, minerals can buildup in your tankless water heating system, resulting in erosion of the walls inside the heating chamber or deposits clogging up the system. This is especially the case if you have hard water.

To properly maintain and clean your water heater, it’s important that you flush the mineral buildup at least once a year. This is where a flush kit comes in.

Regular flushing keeps your unit running smoothly, extending its lifespan so that you can continue to enjoy hot water without any interruptions. An efficient system also means less maintenance and due to this, you get to enjoy smaller energy bills.

Important Features of a Flush Kit – What to Look Out For

Before you go out and buy your flush kit, here are a few key points to keep in mind:

  • Components

Flush kits should contain all the parts and solutions you need to clean your water heating system successfully. A good flush kit should include a powerful submersible pump with a high pump cycle, a long hose (to connect the kit to the heater unit) and a tank or bucket to store the solution. Some kits come with the cleaning solution as well which is easy and highly convenient so make sure to check what your kit contains before you buy it.

  • Compatibility

Not all products are compatible with all heating systems so make sure your flush kit is a universal one that’s compatible with the model of your tankless water heater. Purchasing a kit and finding out later that it won’t work on your heater can be disappointing as well as a waste of money. Alternatively, purchase a flush kit created specifically for use with a specific tankless water heater brand.

  • Safety

The kit should be safe to use on the internal components of your water heater. The kit should not be too heavy and the hose must also be lightweight for easy use, as this will reduce damaging the system.

In terms of safety, check whether the descaler or cleaning liquid contains harsh chemicals. Because the water heater supplies water to your kitchen, you would want to avoid using harsh or dangerous chemicals. Instead, opt for biodegradable and natural cleaners.

You can also use a DIY vinegar solution with most tankless water heater cleaning kits for a safe and natural option. Before using, ensure that the cleaning kit can be used with vinegar. In most cases, the answer is yes.

How to Flush Your Tankless Water Heater

Flushing your tankless water heater isn’t a complicated task but it can take about an hour and some effort, especially if it’s your first time.

You don’t need to hire a professional for this job since learning to do it on your own is quite easy, allowing you to save yourself the extra money and time. After all, this is something that will need to be done periodically.

Here’s a step-by-step guide on how to flush your tankless water heater by yourself.

  • Step One: First, make sure to turn off the electrical circuit at the breaker panel for your water heater. If the heater uses gas, turn off the gas to the unit by rotating the gas cutoff counterclockwise.
  • Step Two: Using a screwdriver, carefully remove the cover plate of the unit to access its wiring. Before you proceed further, take a non-contact electrical tester and hold the tip against the wiring that leads into the terminals. If the tester light turns on, turn off the main circuit breaker to the house just to be on the safe side. Test all the wires again to make sure that the system has no power supply and then replace the cover plate.
  • Step Three: Now, turn off the water supply valve which sends cold water to the heater and then turn off the main hot water valve which sends hot water to all the fixtures in the house.
  • Step Four: Take a 6 ft garden hose and connect one end of it to a pump and the other end to the cold-water isolation valve. Take a second garden hose and connect it to the hot water isolation valve. Then, tighten the hose couplers using an adjustable wrench.
  • Step Five: Here’s where the bucket comes in. Take the open end of the second hose and place it in the bucket along with the pump. Fill up the bucket with up to 5 gallons of clean, fresh white vinegar or the cleaning solution that’s included in your kit.
  • Step Six: Open both the cold and hot isolation valves on your water heater and turn on the pump that you placed in the bucket. This will circulate the cleaning solution through the heater.
  • Step Seven: Allow the pump to circulate for 45 minutes and then turn it off, letting the solution drain away from the water heater, through the hoses and into the bucket. Now close the cold-water isolation valve.
  • Step Eight: Throw away the cleaning solution in the bucket and place the open-ended hose back inside it. Next, turn the cold-water supply valve on and allow the water to flow into the bucket for 5 minutes. Close the valve and disconnect both garden hoses from the inlet valves.
  • Step Nine: After turning off the hot water isolation valve, refer to the owner’s manual for the heater to remove the inlet filter screen. Rinse it well to remove sediments and then reinstall it.
  • Step Ten: Now it’s time to open the valves. First turn on the hot water supply valve and then the cold-water valve. Turn on a couple of your hot-water faucets inside the house to let out any air that could come in from the hot-water lines. Once the air is out, close the faucets.
  • Step Eleven: The final step of this entire process is to check the water heater’s connections to ensure that there aren’t any leaks. Test all the faucets in your house for hot water.

REMEMBER: flushing your water heater without turning off the gas (if it’s a gas heater) or power will damage your unit so opening the unit and verifying that the power is off with a tester is the best way to ensure that all power sources are turned off. Do not skip this step.

The Bottom Line

Flushing your tankless water heater regularly is extremely important if you want to have your unit running smoothly and lasting longer.

Without regular flushing, the interior components of your heater will slowly damage. This will result in reduced efficiency and higher power bills. To prevent this from happening, flush the system regularly as per the manufacturer’s instructions.

Without a proper flush kit, cleaning the components of the heater can be a difficult task so make sure you pick the right kit before you get down to it.

If you want to learn more about tankless water heaters, check our detailed reviews and guide here.

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