Tap water on mounted orchids

[marcoeverard]

What is the view on using tap water for mounted plants? It would be much easier for me to use tap water on a timer for my orchids mounted on cork but I am wondering what your views are on this. I know that hard tap water causes a build up of salts in plants in pots but would this be the same for mounted plants? It is difficult to keep my water butt topped up with rainwater especially if I go on holiday and if I can use tap water on a timer and fertilise seperatley it would make life much easier. Also the pump I have in the water butt doesnt have enough pressure to get all the way around the circuit now that I have so many of my orchids mounted each with individual drip feeds.