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Everything you need to descale and maintain a tankless water heater: flush kits, descaler, isolation valves, filters and covers.
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Every tankless water heater slowly collects mineral scale in its heat exchanger, especially in hard-water areas. Scale reduces efficiency, causes temperature swings and error codes, and can shorten the life of the unit. Regular descaling with a tankless water heater flush kit is the single most effective maintenance task, and most homeowners can do it in about an hour.
| Item | What it does |
|---|---|
| Flush kit (pump and hoses) | Circulates descaler through the heat exchanger for 45–60 minutes |
| Descaler solution | Dissolves calcium and lime scale; food-safe and biodegradable formulas available |
| Isolation valve kit | Hot and cold service valves with flush ports, needed to connect hoses |
| Inlet filter screen | Catches sediment; clean it every time you flush |
| Bucket | Holds 2–4 gallons of solution |
Follow our step-by-step guide to flush a tankless water heater.
A tankless water heater cleaning kit, also sold as a tankless water heater flushing kit or tankless water heater maintenance kit, usually bundles the pump and hoses. A tankless water heater descaler kit adds a bottle of tankless water heater descaler solution. Brand-name options include the Chromex tankless water heater flushing kit, the Hercules Haymaker tankless water heater descaler and the Rinnai tankless water heater flush kit.
Look for a descaler that is compatible with copper and stainless heat exchangers and approved by your unit's manufacturer. Ready-to-use solutions are convenient; concentrates are cheaper for frequent flushing. Descaler is a chemical product: once opened, it cannot be returned (see our return policy).
A tankless water heater valve kit adds isolation valves to units installed without them, and a tankless water heater cover protects piping on outdoor installs.
Most flush kits work with any brand that has standard 3/4-inch isolation valves, including Rinnai, Navien, Rheem, Noritz, Takagi and A.O. Smith. Check the hose fittings on the product page if your valves are a different size.
A typical kit includes a small submersible pump, two washing-machine-style hoses, and a bucket or instructions to use your own. Some kits include descaling solution. You connect the hoses to the unit's isolation valves and circulate descaler through the heat exchanger.
Many manufacturers allow undiluted white vinegar for descaling; others recommend a specific descaler. Check your manual first. Commercial descalers often work faster on heavy scale.
Yes. Isolation (service) valves on the hot and cold lines let you shut off the water and connect flush hoses. If your unit was installed without them, a plumber can add an isolation valve kit.
Most manufacturers recommend at least once a year, and every 6 months or more often in hard-water areas. See our maintenance guide.
