Best Tankless Water Heater Flush Kits (2025)
We compared the top tankless water heater flush kits by pump quality, descaling power, and overall value. Here are the 5 best options for DIY descaling.
HowToDrainAHotWaterHeater.com
February 24, 2025
Mineral scale builds up inside tankless water heater heat exchangers the same way lime coats the inside of a kettle. Left unchecked, it restricts water flow, reduces heating efficiency, and can trigger error codes that shut the unit down. Flushing with a descaling kit is the fix.
A good flush kit includes a pump, hoses that connect to your unit’s isolation valves, a bucket, and a descaling solution. You circulate the solution through the heat exchanger for about an hour, rinse with clean water, and you’re done.
We compared five popular kits based on pump quality, descaling solution strength, ease of use, and overall value.
What to Look for in a Flush Kit
Before comparing kits, here’s what actually matters:
| Factor | Why It Matters |
|---|---|
| Pump flow rate | Higher GPH moves solution through the heat exchanger faster and more thoroughly |
| Descaling solution | Citric acid-based solutions outperform vinegar by about 3x on mineral deposits |
| Hose quality | Cheap hoses kink or leak at the connections, creating a mess |
| Bucket size | Needs to hold the solution plus some overflow, 3.5 to 5 gallons is standard |
| Compatibility | Most kits use standard 3/4” hose connections that fit isolation valve service ports |
The 5 Best Tankless Water Heater Flush Kits
1. Hercules Haymaker Descaler Kit (Our Top Pick)
The Haymaker kit from Oatey/Hercules is what many professional plumbers use. The stand-out feature is the descaling solution itself: a citric acid-based formula that dissolves lime, scale, rust, and sulfates without corroding metal components. It’s VOC-free and non-toxic.
The kit ships with a 550 GPH re-circulation pump, two 5-foot hoses, one quart of Haymaker solution, and a 3.5-gallon bucket.
Why we recommend it: The descaling solution is significantly stronger than household vinegar, roughly three times more effective according to plumber forums and independent testing. If your unit has heavy buildup or you’ve been putting off maintenance, this is the kit to grab.
Trade-offs: The price is higher than competitors. The included 32 oz solution covers one flush cycle, so you’ll need to buy more solution separately for future maintenance.
Check price on Amazon2. Eccotemp EZ-Flush System Descaler Kit
Eccotemp’s kit takes a different approach to design. The pump is built into the bucket, making the entire setup more compact and easier to store. There’s no separate pump to wrangle.
It comes with a 350 GPH built-in pump, two 5-foot rubber hoses, and a quart of NSF/ANSI 60 certified descaling concentrate. The solution is non-toxic and biodegradable.
Why it stands out: The self-contained design is the real selling point. Everything packs into the bucket when you’re done. If you’re short on storage space or want the simplest possible setup, this is it.
Trade-offs: The 350 GPH pump is slower than the Haymaker’s 550 GPH unit, so circulation takes a bit longer. The rubber hoses feel less durable than braided alternatives.
Check price on Amazon3. My PlumbingStuff Tankless Flushing Kit (Best Value)
This kit delivers solid performance without the premium price. It includes a Zoeller floor sucker pump (durable enough for other household draining tasks too), a 5-gallon bucket, two 5-foot hoses, and a quart of Flow-Aide system descaler.
Why it stands out: The Zoeller pump is a step above what most kits include at this price point. The 5-gallon bucket gives you more working volume than the 3.5-gallon options. And the Flow-Aide solution is well-regarded for breaking down mineral deposits.
Trade-offs: Some users have reported mixed quality on the hoses. Consider upgrading to braided hoses if you want something sturdier for repeated use.
Check price on Amazon4. Chromex Tankless Water Heater Flush Kit
A newer entrant that’s gaining traction. The Chromex kit includes a 1/6 horsepower pump, 6-foot hoses (longer than most competitors), a sturdy bucket, and a citric acid-based descaling solution.
Why it stands out: The 6-foot hoses provide extra reach, which matters if your isolation valves are in a tight spot. The citric acid solution is solvent-free and safe for all metals, rubber, and plastics inside the heat exchanger.
Trade-offs: Less of a track record than Hercules or Eccotemp. Fewer user reviews to draw from.
Check price on Amazon5. Kelaro Tankless Water Heater Flushing Kit (Budget Pick)
The Kelaro kit provides the hardware, pump, hoses, and bucket, but does not include descaling solution. You supply your own white vinegar, which keeps the purchase price lower.
Why it stands out: If you already have vinegar on hand, or prefer to buy your preferred descaler separately, this kit gets you the mechanical components at a lower price.
Trade-offs: You’ll need to source your own descaling solution. Vinegar works for light buildup but may not cut it for heavily scaled heat exchangers.
Check price on AmazonQuick Comparison Table
| Kit | Pump | Descaler Included | Bucket Size | Best For |
|---|---|---|---|---|
| Hercules Haymaker | 550 GPH | Yes (citric acid) | 3.5 gal | Heavy buildup, professional results |
| Eccotemp EZ-Flush | 350 GPH (built-in) | Yes (NSF certified) | Integrated | Compact storage, simple setup |
| My PlumbingStuff | Zoeller pump | Yes (Flow-Aide) | 5 gal | Best overall value |
| Chromex | 1/6 HP | Yes (citric acid) | Standard | Hard-to-reach isolation valves |
| Kelaro | Standard | No (bring your own) | Standard | Budget-conscious buyers |
How to Flush a Tankless Water Heater (Quick Steps)
The process is the same regardless of which kit you choose:
- Turn off the unit and close the cold water inlet and hot water outlet isolation valves.
- Connect the hoses from the kit’s pump and bucket to the isolation valve service ports.
- Fill the bucket with the descaling solution (mixed with water per the instructions).
- Turn on the pump and circulate the solution for 45 to 60 minutes.
- Drain and rinse. Disconnect the hoses, refill the bucket with clean water, and circulate for 5 to 10 minutes to flush out residual descaler.
- Reopen the isolation valves and restore power.
For detailed flushing instructions specific to tank-style water heaters, see our How to Flush a Water Heater guide.
When to Call a Professional
If your tankless unit is throwing error codes related to flow restriction or overheating, and a DIY flush doesn’t resolve the issue, the heat exchanger may need professional cleaning or replacement. Error codes vary by brand. Check your owner’s manual for flow-related fault codes before assuming the worst.
Frequently Asked Questions
How often should I flush my tankless water heater?
Most manufacturers recommend annual descaling. If you live in a hard water area (above 120 ppm), every 6 months is better. Some units have a built-in reminder that tracks usage.
Can I just use vinegar instead of a flush kit?
Yes, white vinegar works for mild buildup. But dedicated descaling solutions like Haymaker are about three times stronger than vinegar and work faster on heavy mineral deposits.
Do I need to shut off my tankless heater before flushing?
Yes. Close both the cold water inlet and hot water outlet isolation valves before connecting the flush kit hoses to the service ports.
How long does it take to flush a tankless water heater?
Most flush kits circulate the descaling solution for 45 to 60 minutes, followed by a clean water rinse. The entire process takes about 90 minutes including setup and cleanup.
Will flushing void my tankless water heater warranty?
No. In fact, most manufacturers require regular descaling as part of the warranty terms. Skipping it could void coverage.
Related Guides
- How to Flush a Water Heater — Step-by-step flushing for tank-style heaters
- Signs Your Water Heater Needs Flushing — Warning signs to watch for
- Annual Maintenance Checklist — Complete yearly task list
- How Long Do Water Heaters Last? — Lifespan factors and when to replace
Sources
- Oatey/Hercules — Haymaker Descaler Product Page — Manufacturer specifications
- Eccotemp — EZ-Flush System — Product details and maintenance guidance
- U.S. Department of Energy — Water Heating — Efficiency and maintenance data
HowToDrainAHotWaterHeater.com
Editorial Team
We're DIY homeowners who got tired of paying plumbers $300 to turn a drain valve. Our guides are built from manufacturer documentation, plumbing code references, and real-world experience maintaining our own water heaters.