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Adding tap water to RO water.

12 years ago

Had a visit this weekend from the movers and shakers of Hawk Hills Orchids. They confirmed what I knew before. Tap water in small amounts is a good idea when one waters with RO as the RO system removes everything. Once a month they water their cloud forest plants with tap water, I do the same.

I use MSU fertilizer which is supposed to make up for all of the deficiencies of RO water but the list of chemicals in tap water is endless. Uranium, cyanide, arsenic, cobalt 6 etc etc is all there in minute amounts. Is any of this necessary? I don't think anyone really knows but many good growers expose their plants to the occasional squirt of tap water.

I just rebuilt my watering system and added a tap water input to the storage containers so that I can, once a month, add some tap water to the mix and then continue watering in my usual way.

Nick

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Comments (4)

arthurm
12 years ago
It depends on where you are and what is in the tap water. In fact before the internet came along i happily watered everything with tap water. Nothing much changed except it stopped raining all that much and the dams around this city threatened to dry up so i installed a rain water tank so i could water my orchids when i wanted to rather than when it was allowed.

I am using a complete fertiliser every so often with the tank water so i suppose it is a matter of trusting the fertilizer manufacturer to add a complete suite of essential minerals.
penfold2
12 years ago
If a plant is able to complete its entire life cycle, then it is getting all essential nutrients. Whether additional substances can benefit a plant is debatable, but I tend to believe the negative effect of carbonates and other potentially harmful substances in tap water outweigh the effect of any beneficial substances. If I were concerned about it, I'd probably use a seaweed extract. The ocean contains every element on earth, and an organic supplement like seaweed is more likely to accumulate beneficial substances vs harmful ones.

-Chris
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westoh Z6
12 years ago
It's one of those areas I've heard many different opinions and have always had a question as to why? That said, I usually add about 5-10% non-softened tap water to my MSU fertilized RO water, unless I'm flushing then pure RO no fert or tap.

Now the questions: In nature does rainwater hold these trace elements? Do they get these trace elements in other ways (media, etc..)? Is humans adding the trace elements better than what nature provides?

Bob
orchidnick
Original Author
12 years ago
Rain water holds no nutrient value by itself. The decomposing organic material (monkey poo and hummingbird pee etc) flushed unto the plants probably contains every conceivable element found in nature. The local water company sends a list of the impurities found in our drinking water every year and that list is very long. It does indeed include items like arsenic, cyanide, uranium etc but in unbelievable minute amounts. Neither MSU nor any other fertilizer can match that.

There are good growers who can't even be bothered with the extra expense of MSU and use regular Grow-More or something like it and whose plants look just fine. MSU is already going the extra mile, adding tap water in very small amounts is probably over the top but I see very competent growers do it and I have been doing it for years with no harmful effect noticeable. Hawk Hills has one of the best collection of Dracula in America, their plants are nothing short of spectacular. They have been adding tap water for ever, just part of their routine. Of course it really does not mean much as they are in Pacifica, California where the ppm of tap water is about 50. Their tap water is as good or better than many bottled water brands.

I also grow Discus, a tropical fish from the head water of the Amazon that loves pure water. RO is essential to successful Discus rearing but tap water gets added so that the end result ppm is about 100.

Nick

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