Expected ppm of RO water?

[Brotherly Monkey]

Originally Posted by RoyalOrchids

Just a clarification: ppm (parts per million) is a unit of concentration, not something in the water. Your meter probably measures TDS (total dissolved solids) and expresses the reading in ppm. 1 ppm = 1 mg/l

Installing a softener upstream of an RO unit would just be adding more "stuff" for the RO membrane to remove.

nit picking a bit here: but they actually measure EC and then convert via a calculation to TDS. Unfortunately, there seems to be no standard formula, and the ones currently applied often gve different readings

[Jerry Delaney]

Originally Posted by Ray

Why wouldn't you use water from a dehumidifier? After all, it is just distilled water - the difference being that you're putting the energy into condensing what is already in the air, rather then doing so after putting energy into vaporizing it.

I don't know, Ray. I have heard "tales" when I was whole selling tropical fish not to use water from ac or dehumidifiers. Some species succumbed to high copper levels (supposedly). I have no real proof that this was the real problem and even if it was, would it make a difference on plants. I do know from experience that ONE copper fitting in a 316ss line is enough to render any mammalian cell culture media toxic.
As to EC, TDS or what ever you may call it, I agree that a reading of 40 would seem to indicate some sort of problem. I would make sure that your filter housing has no nicks or gouges in it that may allow some leakage around the o-ring. Also, if your cartridges are old, it doesn't take much more than a pin prick to cause a problem. By the way, Ray is correct in that softening the water first greatly improves RO filtration and extends filter life.

[orchidsamore]

I have to add that this fear of hard water makes me laugh.

My water is 1800 ppm - yes I call it liquid rock - and of course I am a commercial grower with tens of thousands of plants living on this water.

All growers of orchids in Florida have hard water although not necessarily this hard. There are a few plants that benefit from RO water but most do just fine. I never bothered to use RO water as it is very wasteful of our natural resources using 4 gallons of water to make one gallon of RO. I do use RO to drink but not on the plants.

As for salt based water softeners - if they are functioning properly they do not add salt to the water. The salt should be flushed out in the rinse cycle of the softener.

My Ag rep recommended my using water softener water to get lower PH and said if I was worried about the salt to run the rinse cycle twice.

[Ray]

A general comment - when I switched over to using RO water, I saw a pretty significant upgrade in plant appearance and vitality. Yes, subjective, but I am very pleased.

Jerry D - I absolutely agree with the tropical fish potential issue, but they are a lot more sensitive than plants, a lot depends, of course, on the construction of the dehumidifier and the rate of dehumidification (i.e., condense a lot of water in a high RH environment, and the metals concentration will be reduced). One might use a similar argument about rainwater, as it does a fine job of cleaning air pollutants and roof sediment.

Jerry-amore is right that a well-tuned softener should not dump excessive salt into the water. A clean, well-tuned gas heater should not put ethylene into the air either. Unfortunately, mechanical things can get out-of-whack easily and without our knowledge, so we go to measures to avoid them being an issue.

The "wasteful" nature of the RO flush water is always up for debate - and a lot of that is determined by just what you do with it. I have two RO systems - one in the greenhouse, and one for the drinking water and ice from my refrigerator. The flush water from the greenhouse used to go on the floor (where it percolated back into the groundwater supply) for humidification, but now goes into an artificial pond that is used for drinking and bathing by birds, deer, etc., and is a home for MANY frogs. The in-house system flushes down the drain and into my septic system, enhancing its function, and again percolating down into the groundwater.

Those are just two ways to use it; there are others, including zero-waste add-ons.

So how much waste water is produced by a softener? There is the backwash part of the cycle that removes dirt from the mineral tank, and the recharging phase that brings in more sodium while flushing the precipitated minerals from the bed down the drain. Some even come with warnings that they can overwhelm a smaller septic system!

[Masdyman]

I feel no guilt at all in using my 100 GPD RO unit maybe 240 l at worst in summer a week ,when local water authorities leave burst underground pipes for months on end.
I have never considered tap water for my orchids and did not like my rain water storage going very mucky at the bottom and being unable to clean wasn't ideal .
I guess i am a RO lover ,i have had it for approx 2 years now and not changed anything yet just cleaned the filters etc and am still getting water at 12 us(7-8 ppm) . The unit cost me £80 so i cannot complain and parts are not expensive anyway ,even if i purchased a new unit every two years £40 for clean pure water a year is worth it i think .

[nhman]

Thanks again for all that have responded!
I just wanted to update anyone who cares on the latest -
Got my water guy to finally understand what I am doing with the R.O. and by fine-tuning the unit (optimizing the pressure through the unit for one.....), the end result is now under 15 ppm or so, which, from the posting herein, would seem pretty much OK for my orchids.