KNG199ICW inlet filter and heat-exchanger maintenance

Safety comes first

If you smell gas, do not try to light an appliance, touch electrical switches or use a phone in the building. Call your gas supplier from a neighbor’s phone and follow their instructions. If the supplier cannot be reached, call the fire department. Installation and service belong to a qualified installer, service agency or gas supplier.

Source: ICW manual: Important Safety Information

Water softening and ICW heat-exchanger flushing

No flushing is required when a water softener is present and consistently operational. Periodic flushing is required when a softener is absent or is not consistently operational. This clarification applies only to KNG199ICW heat-exchanger flushing. Inlet-filter cleaning, exterior care, inspections and other maintenance remain required. A scale inhibitor, cartridge or filter, including KSCALS, is not a water softener and does not qualify for this exception. Follow the INW manual separately.

Source: manufacturer/user clarification received 2026-10-27, for KNG199ICW: “No flushing is required when a water softener is present and consistently operational. Periodic flushing is required when a softener is absent or is not consistently operational.” Original manuals unchanged.

Source: ICW manual: Required Routine Maintenance

Inlet filter interval

Installation instructions call for initial inlet filter cleaning every six months, with more frequent cleaning when debris is often present. Required Routine Maintenance separately says to clean the filter regularly. This interval is not the INW monthly filter instruction.

Source: ICW manual: Installation; Required Routine Maintenance

Preparation and gentle filter cleaning

Before filter maintenance, disconnect the power supply and power to the outlet, close the manual gas shut-off valve, run a nearby hot faucet until cold, close the hot and cold isolation valves and drain the heater. The manual then describes unscrewing the brass end of the cold inlet assembly, rinsing or gently brushing the screen and securely reinstalling it. Do not tap the screen. If isolation, draining or reassembly is unclear, use a qualified professional.

Source: ICW manual: Clean the Inlet Water Filter

Original ICW manual hardness table, subject to the softener clarification

Source: ICW manual: Installation: hardness treatment and flushing guidelines

Establish the interval without a reliable softener

When a softener is absent or not consistently operational, periodic heat-exchanger flushing is required, including for water at 0–4 grains/gallon. The original manual table above informs hardness-based frequency but does not override the confirmed softener condition. Its grain ranges share boundaries at 4 and 9, and its soft-water “None” row does not establish an interval for unsoftened water. Contact Kings Peak support or a qualified professional to establish the interval for unsoftened 0–4 grains/gallon or boundary values; no frequency is specified here.

Source: manufacturer/user clarification received 2026-10-27, for KNG199ICW: “No flushing is required when a water softener is present and consistently operational. Periodic flushing is required when a softener is absent or is not consistently operational.” Original manuals unchanged.

Source: ICW manual: Installation; Flush the Heat Exchanger

Flushing is recommended for a licensed professional

The manual recommends a licensed professional for heat-exchanger descaling. Its process uses isolated service connections and a circulation pump, continues until the returning solution is clean, then drains the solution and restores normal supplies. It specifies running the heater for at least five minutes afterward to clear remaining solution. It does not prescribe a universal 45–60-minute circulation time or a vinegar concentration.

Source: ICW manual: Flush the Heat Exchanger