LGHT said:
Is there any disadvantage of using RO water? I plan on using nothing but RO water until I put them in the ground. I currently have 5 that I have been giving them RO water only because the water treatment plants here in california can put almost anything in the water at any time. Plus they have been known to change what put into the water and the levels at any time making it very difficult to tell what's in the water. To remedy this I added an RO unit to my kitchen and use only that water to drink and water the plants with.
as Vespucci said, there is a higher cost associated with RO permeate. You would have to pay for the energy to desalinate and there would be membrane cleanings and membrane replacement later on...
The average TDS (total dissolved solids) found in tap water ranges between 500 to 1000 ppm. A standard home desalination skid produces permeate between the range of 5 to 80 ppm TDS, based on membrane age and salt passage
RO permeate can be considered ideal for seedlings in that there are no micro-biological life present and there are low dissolved solids....
The only downside is probably that the pH of RO permeate can tend to be slightly acidic, in some cases as low as 5.0
This acidity depends on the feed water pH and its Langelier saturation index (LSI).
Don't want to go all chemistry like on you but if you are interested in the mechanism of how this happens; basically if there are alot of alkaline ions present in your feed water, this will cause the water molecules to dissociate into H+ ions at a faster rate at the point where osmotic pressure is equal to applied pressure in the RO membrane. When the osmotic pressure is overcome in the membrane, the smaller H+ ions (formed by the presence of the alkaline salts) pass through the membrane together with the water molecules (solvent molecules) into the permeate stream leaving behind the dissolved salts
all in all..........as long as the pH of your feed water is between 7.0 to 7.4 you should have relatively neutral pH in your permeate stream.....
I think WHO standard for potable water is 7.0 to 8.5, hopefully your water company doesn't supply you with the extreme of the specification.....