Exactly. Thanks. This is a ‘non-domestic’ application shall we say. Measuring something with any buffer capacity at all should negate the water’s pH, so shouldn’t be a problem, but the manufacturers advice still doesn’t sit comfortably with me. But they should know!

Has a psion5, brilliant tech. Loved it. The calendar was way ahead of its time, 2AA batteries gave weeks of life and you could just about touch type on the keyboard. If I could get it to synch with office I’d be tempted to dig it out again, it really was the future.