For those of us silly enough to persist with the original window washer system on their bus, and always wondering if the pressure in the washer bottle has leaked away since you last pumped it up... This works for me, cap the inflator umbilical cord with one of these inexpensive tyre pressure checking caps, off the well known marketplace. Leave the cord hanging out for regular visual checks. Another big plus is you will get an extra 3 spares in the set...win, win!
