Ian;

I would like to add:

Depending on the ions, some hard waters can slow down washing. This is due to the decrease in swell caused by Sulfates, and the change in swell due to the pH of some water supplies. For example, water with a lot of Calcium Sulfate or Aluminum Sulfate, which would be slightly acidic (beyond the norm introduced by Carbonate perhaps), would sharply decrease swell.

In addition, Calcium ions tend to slow fixing and washing due to the nature of their effects on hypo.

This is why I suggest running tests with your local water supply, as it can have a major impact on the final times of fix and wash.

PE