OEI..
On a Bell 212, most pilots will turn on the pitot heat (and static vent heaters, as they are usually controlled by the same switch), when it is raining.
There are sometimes water traps in the air pipes, but these don't always work very well, and water in the pitot head can cause lots of problems.
I've never seen water travel as far as the ASI, as there's quite a pipe run to get to it, but I'm sure it has probably happened somewhere.
Before I escaped from Nigeria, we often had problems when it rained, as 212 pitot/static heaters aren't the most reliable things around.
When I was called to a waiting aircraft with this snag, water in the pitot system could easily be removed by sucking very gently (after making sure that the heater wasn't working!!), and this often caused the pax to enquire why the greenie was giving their heli a BJ.