Sampling pipes 21 and 22 are inserted, separated from outlet
openings, into first and second water softeners 4 and 11. Raw water
flows through first water softener 4, and raw water does not flow through
second water softener 11. Once the hardness component concentration of the
treatment water sampled by sampling pipe 21 reaches a specified concentration,
the watercourse selection of valves 2 and 6 and valves 9 and
13 are switched, causing raw water to flow through second water softener
11. First water softener 4 is regenerated by salt water from a salt
water chamber 14. The resulting water softening device prevents the leaking
of hardness components, even with there is a fluctuation in the water quality of
the raw water or when there is performance deterioration in the ion exchange resin.
