When calibrating a pressure switch on a nitrogen backup header would it be acceptable to drop the sensing line and hookup test equipment directly to switch for calibration using a water hand pump?

It's just a shop debate if water could compromise the header. Really whatever water left in the fittings is purged out with nitrogen header pressure before snugging up the fittings.

So what's your take,,,, bad practice? No harm?

 

Better off shop testing with dry gas, that way no worries
If have an existing pressure transmitter on the header, you may be able to do checks without a hand pump.