3-in-1 syringe letting out a splash of water with the air puff

I managed to find out how to change the brown donut o-ring in my 3-in-1 to stop those tiny bits of water sneaking out in the air puff (was making my dentist's life a misery)

Very useful website. Many thanks Anglian Dental.

angliandental.co.uk/how-to-videos/