A tankless water heater flush kit gives you the pump, hoses, and bucket needed to circulate a descaling solution through a heater’s service valves. The best choice depends on what you want included: the Chromex kit comes with an NSF-certified descaler and a larger bucket, while several 6699 options offer a choice of cleaning fluid or a higher-flow pump. Before buying, check your heater’s instructions and make sure the kit’s hoses and cleaning solution are suitable for your model.
Table of Contents
Quick Comparison: Best Tankless Water Heater Flush Kits
| Product | Pump | Bucket | Cleaning solution | Best for |
|---|---|---|---|---|
| Chromex Tankless Water Heater Flush Kit | 1/6 HP | 5 gallons | NSF-certified citric-acid descaler included | A more complete kit with a larger bucket |
| 6699 Tankless Water Heater Flushing Kit | 1/6 HP; up to 1,100 GPH listed | 3 gallons | Not included | A basic kit for use with your chosen cleaner |
| 6699 Descaling Flush Kit with Utility Pump | 1/6 HP; up to 1,100 GPH listed | 3 gallons | Not included | A similar pump-and-hose setup with a compact pail |
| 6699 Cleaning Kit with Cleaner | 1/6 HP; up to 1,100 GPH listed | 3 gallons | Bottle of cleaner included | Getting a cleaner and flushing hardware together |
| 6699 Kit with 1/4 HP Stainless Steel Pump | 1/4 HP; up to 1,500 GPH listed | 3 gallons | Bottle of cleaner included | A higher-flow pump and stainless steel housing |
Our Picks: Best Tankless Water Heater Flush Kit reviews
1. Chromex Flush Kit: Best Complete Setup with Included Descaler
The Chromex kit is a six-piece setup built around a 1/6 HP pump, two hoses, a five-gallon bucket with a lid, and an elevated pump grate. It also includes a citric-acid descaling solution. That makes it a convenient pick if you want the core flushing equipment and a cleaner in one package.
The included solution is described as NSF certified to NSF/ANSI/CAN 60 for drinking water treatment chemicals. Chromex also states that its solvent-free formula is non-corrosive and intended to be safe for use with most metals, PVC, rubber, and ABS materials. Even so, check your water heater’s manual for approved cleaning products and follow the kit’s instructions.
Its six-foot hoses are designed to connect to tankless heater service valves, and the listed compatible brands include Rinnai, Bosch, Noritz, Rheem, Takagi, Navien, and others. The five-gallon bucket gives you more capacity than the three-gallon pails in the other options here. The tradeoff is that this kit does not list pump flow or head figures, making pump-to-pump comparisons harder.
Pros:
- Includes a descaling solution, pump, hoses, bucket, and grate
- Five-gallon bucket offers more capacity than the other kits in this guide
- Descaler is stated to be NSF certified to NSF/ANSI/CAN 60
- Six-foot hoses are intended to connect to tankless service valves
Cons:
- Pump flow and maximum head are not specified in the supplied product details
- Check the cleaner’s compatibility with your heater before use
Verdict: Choose the Chromex kit if you value an included, certified descaler and a larger bucket over detailed pump performance specifications.
2. 6699 Basic Flushing Kit: Best for Supplying Your Own Cleaner
This 6699 kit includes a 1/6 HP submersible pump, two six-foot PVC hoses, a three-gallon bucket, and a lid opener. The pump is listed with a maximum flow of 1,100 gallons per hour and a maximum head of 16.5 feet. Those figures provide a useful point of comparison, though actual flow can vary with the setup and conditions.
No vinegar or biodegradable cleaner is included. The product description suggests mixing one gallon of cleaner with one gallon of water, but you should use only a solution approved for your specific heater and follow the heater maker’s directions. The pump’s listed maximum fluid temperature is 95°F, so do not put hotter liquid through it.
The kit’s main appeal is its straightforward hardware package. It connects to isolation valves using the supplied hoses and includes adapters and washers. Compared with the Chromex option, it has a smaller bucket and no included descaler, but it gives you more freedom to choose a cleaning product that meets your heater’s requirements.
Pros:
- Includes a 1/6 HP pump, two hoses, bucket, adapters, and washers
- Lists pump flow and head specifications
- Includes a lid opener for the pail
- Lets you choose a compatible cleaner separately
Cons:
- Cleaner is not included
- Three-gallon bucket is smaller than the Chromex bucket
Verdict: This is a practical choice if you already have an approved descaler or want to select one yourself and need a basic pump-and-hose kit.
3. 6699 Utility Pump Kit: A Similar Compact Option Without Cleaner
This 6699 model has much the same basic setup as the other 1/6 HP 6699 kit: a submersible pump, two six-foot PVC hoses, adapters, washers, and a three-gallon pail. Its listed pump figures are also 1,100 gallons per hour maximum flow and 16.5 feet maximum head. A lid opener is included as well.
The product description calls for a mixture of one gallon of vinegar or biodegradable cleaner with one gallon of water, but the cleaning product is not included. Do not assume that every descaler is suitable for every tankless heater. Check the heater manual and the cleaner label before connecting the kit. The listed pump fluid temperature limit is 95°F.
On paper, this option is close to the second 6699 kit in this guide. Both have the same stated pump power, flow, head, hose length, and bucket capacity. If you are choosing between them, compare the current listing details and included accessories carefully; the supplied specifications do not show a major performance difference.
Pros:
- Includes the pump, two hoses, adapters, washers, pail, and lid opener
- Lists pump flow, head, and temperature limits
- Six-foot hoses are designed for connection to isolation valves
Cons:
- Cleaning solution is not included
- Its listed pump and bucket specifications closely match another 6699 option
Verdict: Consider this kit if its listing or included accessories suit your needs, but compare it closely with the other 1/6 HP 6699 model before deciding.
4. 6699 Kit with Cleaner: Best for a Ready-to-Mix Package
This all-in-one 6699 kit adds a bottle of cleaner to the familiar 1/6 HP pump, two six-foot hoses, adapters, washers, and three-gallon bucket. The pump is listed at up to 1,100 gallons per hour, with a maximum head of 16.5 feet. It also has a stated maximum fluid temperature of 95°F.
The product instructions call for two to three caps of descaler mixed with two gallons of water. The cleaner label and heater manual should guide how you prepare and use the solution. The listing warns against skin contact and says to read all precautions and directions carefully. That handling note is worth considering if you prefer a milder or separately selected cleaner.
Compared with the first three kits, this model saves you from sourcing a cleaner separately. However, it has the same listed pump power and flow figures as the other 1/6 HP 6699 options, so its main difference is the included bottle rather than a stronger pump.
Pros:
- Includes a bottle of cleaner along with the flushing hardware
- Provides listed pump flow, head, and temperature limits
- Includes hoses, adapters, washers, bucket, and lid opener
Cons:
- Cleaner requires careful handling and label-directed use
- Three-gallon bucket and 1/6 HP pump are similar to the other 6699 kits
Verdict: Pick this package if you want a cleaner included and are comfortable following its handling instructions and checking its compatibility with your heater.
5. 6699 Stainless Steel Pump Kit: Best for Higher Listed Flow
This 6699 kit stands apart with a 1/4 HP stainless steel utility pump. The supplied specifications list a maximum flow of 1,500 gallons per hour and a maximum head of 21 feet, compared with 1,100 gallons per hour and 16.5 feet for the 1/6 HP 6699 pumps. These are maximum figures, not a guarantee of the flow you will get in every setup.
The package also includes two six-foot PVC hoses, a three-gallon bucket, adapters, a lid opener, and a bottle of cleaner. The pump has a listed maximum fluid temperature of 95°F, and its stainless steel housing is described as corrosion-resistant. The cleaner instructions call for two to three caps mixed with two gallons of water and caution against skin contact.
The stronger listed pump may appeal if you want more capacity than the other options provide, but the extra output is not essential for every flushing job. Check your heater’s service instructions and make sure the pump’s limits and cleaning process fit your setup. For a basic, occasional flush, the lower-powered kits may be enough.
Pros:
- Highest listed pump flow and head among the products compared here
- 1/4 HP pump has stainless steel housing
- Includes cleaner, hoses, adapters, bucket, and lid opener
- Lists pump temperature and operating specifications
Cons:
- Three-gallon bucket is smaller than the Chromex bucket
- Included cleaner has handling precautions and must be used as directed
Verdict: Choose this kit if you want the highest listed pump capacity in this group and prefer a stainless steel pump housing; for routine basic use, its extra output may not be necessary.
How to Choose a Tankless Water Heater Flush Kit
Check your heater’s service-valve setup
Most kits in this guide are designed to connect to tankless heater isolation valves using six-foot hoses. Before ordering, confirm that your heater has the required service valves and that the hose fittings and adapters match. If you are unsure, check the heater manual or ask a qualified plumber rather than forcing a connection.
Match the cleaner to your water heater
Some kits include a descaler, while others leave the choice to you. Follow the water heater manufacturer’s instructions for approved cleaning products and mixtures. Do not assume vinegar, citric acid, or a supplied cleaner is right for every model. Read the cleaner label, including any dilution and handling directions.
Compare pump power and listed performance
The 6699 kits offer either a 1/6 HP pump with a listed maximum flow of 1,100 gallons per hour or a 1/4 HP model listed at 1,500 gallons per hour. The higher figures may be useful when comparing the products, but actual performance depends on the installation and conditions. The Chromex listing gives pump horsepower but does not provide flow or head numbers.
Consider bucket size and what comes in the box
The Chromex kit includes a five-gallon bucket; the 6699 kits include three-gallon pails. Also check whether you need to buy a cleaner separately. A kit with a solution included can save a separate shopping step, while a hardware-only package gives you the option to select an approved product yourself.
Pay attention to temperature and safety limits
The 6699 pump specifications list a maximum fluid temperature of 95°F. Keep that limit in mind and follow the heater and kit instructions before starting. Use cleaners only as directed, take the precautions on the product label, and avoid contact with solutions that carry skin-contact warnings.
Think about how often you will use the kit
If you only need the equipment for occasional maintenance, a basic 1/6 HP kit may meet your needs. A higher-capacity pump can be appealing, but it is worth paying attention to the features you will actually use. If you do not want to source cleaner separately, compare the included-solution kits and confirm compatibility before purchase.
Frequently Asked Questions
What does a tankless water heater flush kit do?
It provides a pump, hoses, and a container to circulate a cleaning solution through a tankless water heater’s service valves. The process is used to remove scale buildup, but you should follow the maintenance steps and cleaner recommendations in your heater’s manual.
Can I use vinegar with these kits?
The descriptions for two 6699 kits mention vinegar as an option, but that does not mean it is suitable for every heater. Check your water heater’s instructions before choosing vinegar or another cleaner, and follow the correct mixing directions.
Do all of these kits include descaler?
No. The Chromex kit includes an NSF-certified citric-acid descaling solution, and two of the 6699 kits include a bottle of cleaner. The other two 6699 kits do not include a cleaning product.
Are these kits compatible with every tankless water heater?
The Chromex listing names several compatible brands, and the 6699 listings describe hoses that connect to isolation valves. Compatibility still depends on your heater’s model and valve connections. Check your manual and the product listing before buying.
How often should I flush my tankless water heater?
Maintenance timing depends on your heater manufacturer’s guidance and your water conditions. Consult the manual for the recommended schedule rather than relying on a one-size-fits-all interval.
Can I pump hot water or hot cleaning solution through the 6699 pumps?
The 6699 pump listings specify a maximum fluid temperature of 95°F. Follow that limit and the product instructions. The supplied Chromex details do not state a maximum fluid temperature, so check its instructions before use.
Final Recommendation
For a well-equipped package with an included, NSF-certified descaler and a larger bucket, the Chromex kit is the strongest all-around choice in this group. If you want to choose your own cleaning solution, consider one of the basic 6699 kits. The 6699 kit with a 1/4 HP stainless steel pump is the option to compare if higher listed flow is your priority. Whichever kit you choose, verify valve fit, cleaner compatibility, and operating limits before starting the flush.
