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628 & 698 Models
Descaling Guide
Reservoir Model
Scale deposits will occur whenever water is heated. Higher deposits will occur with harder water and higher
temperatures. Although scale deposits can be reduced through using softened water this is not necessarily
desirable due to the adverse effect on taste. Therefore, it is important that descaling is carried out regularly to
maintain the high efficiency of operation of your appliance.
The frequency of descaling depends on the hardness of the water and the intensity of usage in each case. At least
every 12 months is highly recommended. Although it is primarily the Hot Tank (Water Heater) that requires
descaling, it is also necessary to sometimes carry out some in the cold tank.
Please note: Descaling is to remove the inevitable build up of limescale and should not be
confused with sanitisation, which is a different procedure for maintaining the necessary
hygiene standards for drinking water.
1. Switch off the power and water supply. Drain off water, including Hot Tank. It may be beneficial at this stage to
flush through the hot tank with clean water to remove as much loose scale as possible if the tank appears
particularly scaled up.
2. Carefully fill a suitable pouring jug with approx 2 ½ litres of hot water and add the correct amount of descaler
relevant to the enclosed instructions for safe and effective use.
3. Remove the Top Cover from the appliance (and the lid covering the cold tank on later models).
Carefully remove the Float Valve and Baffle Plate from the Cold Tank.
4. Slowly pour the descaling solution into the Cold Tank. This will drain directly into the Hot Tank. Continue to add
the solution until it also just begins to fill the Cold Tank too. Leave the solution to react with the limescale as
directed.
5. Should limescale be present in Cold Tank, carefully treat the areas concerned using the same solution. Also,
treat any removed parts such as the Float Valve, after checking the directions for use for compatibility. Similarly,
if the outlet taps need treatment, dispense a little solution to draw it into the taps. Examine the small black
rubber water stop seal on the Float Valve for any damage or wear and replace if necessary. DO NOT ROTATE
THE SEAL IF IT IS NOT BEING REPLACED AS THIS COULD AFFECT ITS WATER SEAL SEATING AND ALLOW
SEEPAGE.
6. After an appropriate time, carefully scrub any surface scale to remove it taking care not to damage the part. If
scrubbing of the inside of the taps is required, remove the Front Panel of the appliance and carefully dismantle
the taps by unscrewing the ring under the lever and then drawing the lever mechanism upwards out of the body.
N.B. Before removing the taps, drain off any remaining solution in the cold tank.
7. Reassemble any removed parts as necessary and flush appliance through thoroughly with mains water as
directed (Carry out sanitisation procedure at this point if desired).
8. Finally, allow appliance to refill, check for any leaks and switch on power supply.
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