Christian McArdle wrote:

Ion exchange works very well.


To add to this, there are considerable differences in ion exchange water
softeners. The two main differences are the method of regeneration and the
flow rates of the system.

Maximum flow rates and pressure drops vary from valve design to valve
design. All are suitable for topping up a loft tank. However, a house on a
mains pressure system, such as a combi boiler, unvented cylinder, or heat
bank must choose wisely to ensure that the pressure drop for the expected
flow rate is low, and that the system is capable of performing the ion
exchange at such a high flow rate without letting hard ions through.

When installing a high flow rate system, it is best to throw away the
washing machine hoses provided and use full bore valves and fixed pipework,
leaving only the valve and cylinders to reduce flow rate capacity.

As for the method of regeneration, there are many strategies. The cheapest
is to use a timer to regenerate in the middle of the night every 'x' days.
The disadvantages of this is that the system may regenerate too frequently
when usage is low and run out with usage is high.

A metered system regenerates after a certain amount of water is used. This
prevents wastage, but means that regeneration may occur at an inconvenient
point and allow hard water through.

A combination system will regenerate during the night after the system is
mostly depleted. Some systems of this type are very sophisticated and will
predict your usage depending on past usage to determine the best time to
regenerate. Some can do a non-full regeneration if they consider it optimum.

The best systems, however, simply have two canisters. When the metering
indicates a change, the system swaps over and the depleted canister is
regenerated. This gives soft water 24 hours a day and minimum wastage of
water and salt. These systems typically cost much more, around the 1000
pounds mark, rather than 500 for a high flow rate sophisticated meter, or
300 for a cheapo timed version.


And at £5 a month for salt, that's a lot of months before they pay for
themselves.



Christian.