Tankless Water Heater Flush Kit: Your Complete Guide

Using a tankless water heater flush kit can help you perform routine maintenance on your water heater. These handy kits come complete with everything you need to flush limescale and keep your tankless heater performing at it's best.

This article will cover how to purchase a tankless water heater flush kit and how to use it effectively. We'll show you a few of our favorite kits to help you begin shopping, and even help you build your own! 

What is a Tankless Water Heater Flush Kit?

A tankless water heater flush kit includes everything you need to flush your tankless water heater. The majority of kits include 2 hoses, a bucket, and a submersible pump, as well as descaling solution to clean the internal parts and heat exchangers.

Why You Need a Flush Kit

The single most important thing you can do for your tankless water heater is to flush it on a regular basis.

As your tankless water heater works, it develops mineral deposits on the heat exchangers and internal parts.

The mineral deposits (called limescale) are a natural occurrence when water is heated. The harder your water, the more limescale will develop, and thus the more frequently you'll need to flush your tankless heater.

> > Learn More About Hard Water < <

Limescale build-up isn't harmful to you, but it does cause big trouble to your tankless water heater. As it accumulates it'll reduce the efficiency of the water heater and cause it to work harder than it should.

This can cause your tankless water heater to experience premature wear and tear.

As a general rule, the manufacturer will not cover replacement or repairs, even if your unit is under warranty!

This video explains the importance of flushing your tankless water heater and how hard water can affect its operation.

Watch the Video

How to Use a Tankless Water Heater Flush Kit

At first it may seem overwhelming, but actually flushing your tankless is not a difficult task, especially if you have isolation valves installed. The whole process will take you roughly one hour.

Here's How to Use a Tankless Water Heater Flush Kit:

Step One:

1.  Disconnect the power to the water heater.
2. Close the hot and cold isolation and service valves. Remove the service caps.
3. Pour 1-gallon of water into your bucket.
4. Connect a hose to the pump.
5. Connect the other end of the hose to the cold service valve.
6.  Place the pump into the bucket and add the descaler solution (add water if instructed).
7. Connect the second hose to the hot service valve, and place the other end into the bucket.
8. Open both the hot and cold service valves and turn on the pump.

Step Two:

1. Allow the pump to circulate the descaler solution through the water heater for about 30 to 45 minutes. Then turn off the pump.
2.  Close the cold service valve and remove the hose from both the valve and the pump.
3. Discard the descaler solution from the bucket.

Step Three:

1.  Open the cold isolation valve and allow the water to exit through the hot service valve into the drain or a bucket for 3 to 5 minutes.
2. Once you're finished flushing, close the hot service valve and remove the hose and replace the service cap.
3. Open the hot isolation valve and connect the power to the water heater.

Watch the Video

Isolation Valves

Most manufacturers do not automatically include a set of isolation valves with their tankless water heaters. Many reputable plumbers will install them regardless of whether they are included, since they understand the importance they play in flushing your tankless.

If your tankless water heater does not have isolation valves, you should consider purchasing a set.  Although you can flush your tankless water heater without isolation valves, having them installed makes the task so much easier.

Best Tankless Water Heater Flush Kits

Surprisingly, there are quite a few different tankless water heater descaling kits on the market today. Many manufacturers offer specific kits, such as the Rinnai Tankless Water Heater Flush Kit, but in most cases it's not necessary to purchase a name brand kit, since they all basically have the same components and work the same.

Here are a few of our favorite tankless water heater flush kits:

My Plumbing Stuff Descaling Kit

The My Plumbing Stuff Descaling Kit is not only our number one pick, but it is also the kind of kit you'd put together yourself. It takes advantage of all of the best components without committing to a particular brand name.

With over 100 years of experience, the experts at My Plumbing Stuff have put together the tankless water heater kit they would purchase. They've selected two 5-foot stainless steel hoses, a 32-ounce bottle of Whitlam FLOW32 Descaler Solution, and a Zoeller 42-0007 Floor Sucker Pump. There's even a 5-gallon bucket to complete the kit and store the supplies when not in use.

The Zoeller 42-0007 Floor Sucker Pump has a 5-foot head and can pump 900-gallons per hour. This is by far the strongest pump on our list and will significantly lower the time necessary to perform the task.

The Whitlam FLOW32 Descaler is arguably the best descaler on the market and is designed to dissolve water scale and other water-formed deposits from tankless water heater systems.

Whitlam Flow Aide Flush Kit

The Whitlam Flow Aide Flush Kit comes with everything you need to flush your tankless water heater, including one of the best descaler solutions available.

The two rubber hoses are designed to work with 3/4-inch service connections, which is the most common size on tankless water heaters. The 3.5-gallon bucket has the flushing instructions printed on the outside for easy reference, and when you're finished, it stores all the components and even has a lid to ensure everything stays together when not in use.

The 350 gallons per hour (gph) pump easily pumps the Flow Aide Descaler solution through your tankless water heater.

This kit comes with one-quart of Flow-Aide which is designed to tackle the most challenging water scale, rust, and lime deposits. But it's also safe, non-flammable, non-toxic and non-corrosive. In fact, it's even biodegradable! 

EccoTemp EZ-Flush System DeScaler Kit

One of the unique aspects of the EccoTemp EZ-Flush System DeScaler Kit is the 3-1/2 gallon bucket. It's not only compact, easy to store with a convenient handle for carrying, but it's also the pump!

Simply connect the hoses directly to the bucket and flip the switch. No need to juggle a pump! It's capable of pumping 350 gallons per hour.

The EccoTemp Ez-Flush System comes with everything you need, including descaling solution, 2-rubber hoses and one-quart of EccoTemp Descaler which is NSF/ANSI 60 Certified and designed for potable water systems. It's also non-toxic, non-corrosive, and biodegradable.

Although EccoTemp is a tankless manufacturer, this kit can be used on other tankless water heater brands as well. The system comes with a 1-year guarantee and 24/7 support.

Chromex Tankless Water Heater Flush Kit

The Chromex Tankless Water Heater Flush Kit is another kit with a quality pump and descaling solution.

The 1/6-hp pump sits on an elevated pump grate within the 5-gallon bucket and can clean the limescale from your tankless water heater in roughly 30-minutes.

The kit also includes two color coded 6-foot rubber hoses and a quart of Chromex descaler solution, which is citric acid based and solvent free. It is safe for use on the majority of metals, PVC, rubber, and ABS plastic hoses. In addition, its non-corrosive and safe for potable water systems.

How to Build Your Own Tankless Water Heater Flush Kit

If you don't already have a submersible pump, it makes since to purchase a tankless water heater flush kit since it'll include all the components you'll need to flush your tankless heater.

However, if you already have a submersible pump, or you just want to put your own kit together with hand-picked components, you may want to build your own kit.

Here's what you'll need:

Submersible Pump

The submersible pump is the most expensive piece to a tankless water heater flush kit, and its arguably the most important. After all, without a pump nothing happens! 

We recommend purchasing the best pump that makes sense for your budget.

The more powerful pumps will be able to circulate the descaling solution faster through your tankless, which can either reduce the time you spend or do a more thorough job. It's really your choice on how you want to use the extra power.

If you're looking for a budget-friendly option, you may want to consider the Superior Pump. It's a solid performer and comes in a variety of different sizes.

Our favorite pump is the one that's included in the My Plumbing Stuff Descaling Kit. The Zoeller Floor Sucker Pump is significantly more expensive, but it's also a very powerful pump.

Descaling Solution

The descaling solution is what the pump circulates through the tankless water heater, and it's what removes and cleans the limescale from the heat exchangers and other internal parts.

Most commercial descalers are chemical based solutions which are acid-based and use compounds such as hydrochloric acid which interacts with alkaline carbonate elements, otherwise known as limescale.

The chemical reaction dissolves the limescale by producing both CO2 (carbon dioxide gas) and soluble salt, which is easily flushed away.

Many descaler solutions, such as the Whitlam FLOW32, are eco-friendly and bio-degradable. 

Check your tankless water heater's owners manual for the manufacturers recommendation on descaling solution. Many recommend using white vinegar which can be purchased at your local grocery store, but some prefer a non-corrosive solution such as the Whitlam FLOW32 Descaling Solution.

Hoses

The next thing you'll need is two hoses. Although, not necessary, we recommend purchasing color coded hoses. It can be helpful since you'll be able to see the connection points at a glance. 

Washer hoses have connectors on both ends, which will enable you to connect one end to the pump and the other to a service port. They are also inexpensive and should last a long time.

We recommend purchasing hoses that are 5 to 6-feet long, as this will give you plenty of length to work with.

Bucket

The last thing you'll need is a bucket. Of course, you can purchase one, but chances are, you already have one laying around somewhere.

It should have a capacity of at least 3.5 to 5-gallons, and when its filled with descaling solution the pump should be fully submerged. 

The bucket should also be clean of debris and chemicals, and it's always a good idea to dedicate it to the task so that you can store your supplies in between flushing.

Common Questions

Here are a few common questions people ask in regards to flushing their tankless water heater:

Can I Flush My Own Tankless Water Heater?

Yes, absolutely! We recommend purchasing a kit or building your own tankless water heater flushing kit so you'll have everything you need, but the process is straightforward and not difficult. 

Many homeowners are intimidated and procrastinate this important maintenance task. If this sounds like you, we suggest hiring a professional plumber to do your first flushing. You can observe, take notes, and ask questions. The next time it's time to flush your tankless, you'll know exactly what to do.

Do Tankless Water Heaters Need to be Flushed?

Yes! The single most important thing you can do to care for your tankless water heater is to flush it on a regular basis. 

If you don't remove the limescale build-up it will lower the efficiency of the tankless appliance and cause it to work harder to perform it's job. This puts unnecessary wear on the heat exchangers and other internal parts, which will cause your heater to breakdown. 

It's important to note, that many manufacturers will not cover warranty repairs if the failure was due to lack of maintenance. And not flushing your tankless water heater falls into this category.

What Should I Use to Flush My Tankless Water Heater?

There's a number of commercial products on the market, and the majority of kits come with a product that you can try. If you like the results, you can purchase more for future flushings, or you can try a different product.

One of the most popular descaling solutions is the Whitlam FLOW32, or you can check your owners manual for recommendations.

A less expensive, but equally effective solution is to use white vinegar. Although, we always recommend checking with the manufacturer before using.

How Much Does it Cost to Flush a Tankless Water Heater?

If you need to purchase a tankless water heater flushing kit, you'll probably spend $150 to $200. But once you have the kit, the only thing you'll need to purchase will be the descaling solution, which will run around $20 to $25.

The cost is minimal compared to the improved efficiency your tankless will deliver. It'll also reduce future repairs and maximize the appliance's service life.