[JLu]

Guys, I'm not being smarter-than-thou in this post, however I actually have academic credentials relating to this issue. That does not mean that I know more than anyone else with experience on the subject, but it does mean that I'm trying to talk science and avoid some of the misinformation that is prevalent on the internet and unfortunately gets repeated over and over and becomes faith based belief. Hopefully you will take it as offered...an effort to present some scientific facts. Unfortunately my history with facts on internet forums leaves me a little gun shy which is why this preamble is so lengthy.

Chlorine in the water supply will not hurt your plants. Chlorine in the water supply is volatile and will gradually vaporize out of water left standing for couple of days. Because of that shelf life issue, water companies have largely quit using chlorine to prevent biological growth in treated water. They now use a chemical commonly referred to as chloramine. Think of it as a combination of chlorine and ammonia. It is not volatile and will not not vaporize from the water left standing. It also will not hurt your plants, but as many of you know will kill fish and must be treated before use in aquariums or ponds (previously chlorinated water for fish could be treated by standing around in an open container).

Second issue...hard water and orchids. So called hard water is water containing dissolved salts from the earth that have low overall solubility...mainly the carbonate salts of magnesium and calcium. Both these elements are used by plants, but the problem is that they deposit onto your planting medium as the water evaporates. Since they are only slightly soluble, they are difficult to remove once they deposit. Thus the very good advice to minimize this accumulation of harmful salts by flushing frequently.

Third water softeners...here is the real danger. Many companies provide water softeners to homeowners in hard water areas to improve the ability of the water to make soap suds and prevent "bathtub rings" which are the same magnesium and calcium salts we are talking about here. Water softeners work by taking magnesium and calcium ions out of solution and substituting sodium ions which are very harmful to your plants. So you remove Ca and Mg which are OK for the plants (as long as you minimize insoluble deposits) and substitute Na (sodium) which which is deadly to plants. NEVER use softened water for plants, not even once.

RO (reverse osmosis) and distillation remove all ions from solution and provide excellent water for orchids. Be sure to use a fertilizer that replaces some of the Ca and Mg which now is not in your water.
RO is pretty wasteful, but it works. Be careful because units are rated on input water capacity, not output of pure water. So a 100 gal/day RO unit uses 100 gal of water daily and wastes 66 gallons and makes 33 gallons of pure water. Distilled water from WalMart is 64 cents a gallon and I have tested it to be sure it is distilled and it is.....not spring water...not some other kind of hyped water..distilled water.

I use rainwater collected off my GH roof. In a pinch, distilled water is great. Tap water is OK as long as you flush thoroughly every watering. Leaving water sit out does nothing. DO NOT use softened water. RO is great, but expensive to obtain if you need much.

Thank you who actually got this far.