How can I tell water pressure is too high for the washing machine?
Water pressure gauges that connect to garden hose fittings are common at home stores in the US.  I assume you are from elsewhere because of the units you used for pressure, but, for instance, at Home Depot the gauges are found in the lawn sprinkler area because water pressure is an important consideration for the design of a sprinkler system.



You may have to look around at stores that sell irrigation or general plumbing supplies to find one.  For an online search "water hose pressure gauge" should give plenty of results.  Of course I'm also assuming that your washing machine uses the same fittings as a garden hose, so make sure you get the right connector (again, standard in the US).