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It will of course always be necessary to identify how water got into the system and stop any water leaks.
Below: The DIGI Cell provides a test for water in oil
Info Centre >> Fuel and Lube Oil Technical Manual >> 7. Lube Oil - Test Results >> 7.6 Hydraulic Oil >> 7.6.2 Water
Water Contamination in Hydraulic Systems
Hydraulic systems are generally very intolerant to water contamination. The action to be taken if testing shows appreciable water contamination will depend on whether the water appears to be emulsified, whether the water is fresh of salt and whether the particular system had the means within it to remove water from the circulating oil (e.g. a filter coalescer unit).
Essentially, the decision will be between changing the oil and attempting to reduce the water content in the system.