The short answer
Rinnai's flushing guide uses 4 gallons of undiluted white vinegar and says never to use chemical solutions in its heaters. Commercial tankless descalers are sold to replace or boost vinegar in the flush bucket. Whichever you use, it is circulated through the heat exchanger by a flush pump and rinsed out afterwards.
Side by side
| White vinegar | Commercial descaler | |
|---|---|---|
| Maker guidance | Named in Rinnai's procedures | Check the manual |
| Quantity | About 4 gallons (Rinnai) | Per the label |
| Circulation | Up to 45 minutes (consumer guide); at least 1 hour at 3-4 GPM (SENSEI bulletin) | Per the label and manual |
Descalers in the catalog
Descaling solutions: American Valve ScaleRX34 Tankless Descaling Solution, Chromex CXT1-1102 Tankless Descaling Solution and Chromex DHX1-1056 Tankless Descaling Solution.
Products mentioned
Descaling solution · American Valve
American Valve ScaleRX34 Tankless Descaling Solution
Descaling solution
Descaling solution · Chromex
Chromex CXT1-1102 Tankless Descaling Solution
Descaling solution · most all tankless water heater
Descaling kit · Chromex
Chromex CXTE-1694 Tankless Flush Kit
Descaling kit · most all tankless water heater
Questions readers ask
Is descaler better than vinegar?
Not necessarily. Use what your heater's maker names; Rinnai's procedures call for white vinegar and warn against chemical solutions.