Tap water

[Shadowmagic]

So you probably know Miss Orchid Girl on youtube. Have learnt a lot watching her videos and I came across this video which made me laugh

[SouthPark]

I don't know a great deal about 'orchidgirl'. But is your post purposely for drawing attention to orchidgirl for some reason, and/or bringing their youtube argument onto here? Or is it to just convey your opinion on it?

About tap water - I'm thinking that - if humans can handle it, then orchids can generally handle it. It might also depend which part of the world we live in - such as different regions have their own ways of treating the water. I think in our region, we have flourides (or something) added to our water --- but not 'chlorine'.

I've used tap water for many many many years for watering orchids ----- every single one of them. No problems at all. But - once again, it probably depends on the region we live in.

Perhaps for professional growers and people with super special plants, then full control is needed - including exactly what is in the water.

[Ray]

Her videos share a lot of information; some of it good, a lot of it bad.

As to the chlorinators, my water system here has quite pure water. They add chloramine about 8 months of the year and chlorine the other 4. After 30+ years of using RO, I can see no harm from either for the last 3.

The reason for avoiding using mineral water is precisely because of the mineral content. Orchids have evolved to live off of very pure water with little mineral nutrient content, so it makes sense to me that they'd do better in our culture if that continued. Mineral waters are called that because, compared to "ordinary" water, they have elevated levels of dissolved minerals - taking them in the exact opposite direction we'd like to go. Then we can add to that the fact that they don't publish what those minerals are, so it is an unknown factor.

Yes, it is likely that those minerals can be beneficial to the plant, but too much of a good thing can be bad! Excessive calcium, for example, can preclude the uptake of other nutrients.

[Subrosa]

Some mineral water contains appreciable levels of sodium, which is really bad news for plants.

[Roberta]

There's tap water and then there is tap water... Whether it is good, bad, or in between depends on its composition, which one must learn from one's local water supplier. In my own part of the world, San Franscisco has fantastic water - suitable for watering even rather delicate Pleurothallids. (around 30 ppm TDS) Parts of San Diego have water with such high mineral content that it damages all but the toughest of orchids (600-900 ppm TDS). Cymbidums and larger Catts are OK, some Paphs actually like it, but serious hobbyists who want to grow a variety of orchids have RO systems. Also, orchids can tolerate much higher solids levels from calcium than from sodium - again, this is a local issue. Just about the only generalization that can be made about all tap water is that it is wet.

[claypot]

I use rain water whenever I can, but sometimes it just runs out in long dry summers so tap has to be used. When that happens I always draw off the water at least 24 hours before intended use using as much pressure as possible to agitate the water. Then leaving open for 24 hours allows some of the gasses to dissipate.
I was always told never to use water from a domestic softening system because of the salts. Never understood which salts but it seemed to make good sense to me.

[Roberta]

Originally Posted by claypot

I was always told never to use water from a domestic softening system because of the salts. Never understood which salts but it seemed to make good sense to me.

I have never had any problem with watering straight out of the tap... no need to let the water sit. It might make a difference with fish, but for plants anything that would dissapate in 24 hours will be gone much faster as the water evaporates.

"Hard" water typically contains calcium, usually as bicarbonate but could also be sulfate. It tends to make a sticky deposit with soap, and also tastes a bit "chalky" - chalk is mostly calcium carbonate. So... what a water softener does is swap those calcium ions with something that tastes better and doesn't make a precipitate with soap, most commonly sodium.(Two sodiums for each calcium... that's the chemistry) So the end product is rather high in sodium, which is bad news for plants (and probably not great for heart patients either) There are potassium-based water softeners (potassium chloride costs a lot more than sodium chloride, so not as common), the end result isn't as bad but plants don't necessarily like that much potassium either. (calcium is pretty much OK for plants, it tends to raise the pH if it is in the bicarbonate form but is otherwise pretty innocuous chemically)

[Ray]

Originally Posted by claypot

I use rain water whenever I can, but sometimes it just runs out in long dry summers so tap has to be used. When that happens I always draw off the water at least 24 hours before intended use using as much pressure as possible to agitate the water. Then leaving open for 24 hours allows some of the gasses to dissipate.
I was always told never to use water from a domestic softening system because of the salts. Never understood which salts but it seemed to make good sense to me.

Water softeners use ion exchange resins to remove the "hard" minerals - calcium-, magnesium-, and iron carbonates - and replace them with sodium chloride.

[Orchid Whisperer]

Shadowmagic, I don't know how common this is in the Netherlands, but in the USA, the water utilities that provide tap water test the water extensively, and in most cases provide that testing data online. I imagine it is similar in the Netherlands?

First find out if that testing data is available for your tap water. I would look for the following list (it is important to write down the units they use, e.g., mg/L, uS/cm, etc):
Most important
Total dissolved solids
Electrical Conductivity (or specific conductance)
Hardness
Sodium
Calcium
Magnesium

Also useful
Sulfate
Other metals
pH