Annual descaling of the KHT100SS tank
In hard water areas (above 7 GPG), mineral scale accumulates inside the KHT100SS tank on the heating element. Scale reduces heating efficiency, increases recovery time, and eventually causes element failure if not addressed. Annual descaling in moderately hard water; every 6 months in very hard water (above 15 GPG).
Descaling procedure: (1) Turn off the cold supply valve and the power to the tank. (2) Allow the tank to cool to below 120F (approximately 30-60 minutes -- do not accelerate cooling by adding cold water). (3) Disconnect the supply tube at the tank cold inlet. (4) Mix a descaling solution: 1 quart of white vinegar + 1 quart of water. (5) Pour the solution into the tank through the cold inlet tube connection with a funnel. (6) Allow the solution to soak in the tank for 2-3 hours. (7) Drain the tank through the hot outlet (hold the faucet open while draining). (8) Reconnect the supply, fill the tank with clean water, power on, heat to setpoint, then drain again (flush). (9) Repeat the clean-water flush once more, then return to normal use. If the tank has heavy scale visible through the opening, repeat the descaling cycle before flushing.
O-ring and seal inspection
Inspect the faucet stem O-ring annually -- the O-ring seals the faucet stem against the faucet body at the hot water outlet. A worn O-ring causes dripping from the faucet even when closed. The KHT100SS faucet uses a standard 1/4-inch O-ring (Parker or Buna-N 70 durometer, 1/4 OD, 1/8 ID) available at hardware stores. To replace: remove the faucet handle cap screw, remove the handle, and pull the stem assembly upward -- the O-ring is visible at the stem base and can be pried off with a non-metallic pick and replaced in 5 minutes.
Thermostat adjustment
The KHT100SS temperature is adjusted via a slotted screw on the tank thermostat body (accessible through the tank front panel, no tools beyond a flathead screwdriver). Clockwise increases temperature toward 210F; counterclockwise decreases toward 140F. After adjustment, allow 15 minutes for the tank to stabilize at the new setpoint before testing output temperature with a cooking thermometer. If the thermostat fails to maintain temperature (output varies more than 10F from setpoint), the thermostat should be replaced -- contact Kraus customer service for the replacement part number for your specific KHT100SS production run.