EcoSmart electric tankless heaters require periodic descaling to maintain heating efficiency and prevent fault codes. Unlike tank water heaters where scale settles to the bottom, tankless heaters concentrate scale on the heating elements where it directly degrades heat transfer.
How scale builds up
Hard water contains calcium and magnesium carbonates that precipitate as scale when water is heated. In tank heaters, scale settles to the bottom. In tankless heaters, scale forms a coating on the heating elements as water flows past. This coating insulates the element from the water, requiring more energy for the same heat transfer and eventually causing element overheating and fault codes.
Descaling frequency by water hardness
- Soft water (under 3 grains/gallon): every 24–36 months
- Moderate water (3–7 grains/gallon): every 18 months
- Hard water (7–10 grains/gallon): every 12 months
- Very hard water (over 10 grains/gallon): every 6 months OR install softener upstream
Don't know your water hardness? Test kits are $10 at hardware stores or available from your water utility on request.
Descaling procedure
- Shut off power and water: turn off breaker, close cold supply valve, close hot outlet valve at fixture.
- Connect descaling setup: attach a recirculation pump to the cold inlet service port and a discharge hose from the hot outlet service port to a 5-gallon bucket. If your install doesn't have service ports, descaling requires removing piping — strongly consider retrofitting service valves for future maintenance access.
- Fill bucket with descaler: 3 gallons of white vinegar or commercial descaler (EcoSmart-approved) into the bucket. Submerge the pump.
- Circulate for 45 minutes: the pump pulls descaler through the unit and back into the bucket continuously. Run for 45 minutes to fully dissolve scale on elements.
- Flush with fresh water: disconnect descaler bucket, flush 3–5 gallons of fresh water through the system to remove residue.
- Restore service: reconnect plumbing, open valves, restore power.
Critical tools
Service valve kit ($60–120) — strongly recommended if your install doesn't have one. Includes 3-way valves at cold inlet and hot outlet that let you isolate the unit for descaling without disconnecting plumbing. Recirculation pump (any small utility pump, $40–80). 5-gallon bucket. White vinegar (~$15 for the volume needed) or commercial descaler ($25–40).
Signs you need descaling now
- Recovery time has increased (it takes longer for hot water to reach the fixture)
- Flow rate at fixtures has decreased
- Outlet temperature varies during sustained use
- Fault codes related to overheating or flow restriction
- Unusual sounds during heating (popping or rumbling on the elements)
When DIY descaling isn't enough
If you've never descaled and the unit is 3+ years old in hard water, the scale buildup may be severe enough that vinegar isn't aggressive enough. Commercial descaler (citric acid or sulfamic acid based) handles heavier buildup. If the unit still shows poor performance after descaling, the heat exchanger or elements may need replacement.