Whoa!!! I think Pat has unnecessarily painted a real scary picture there.

The continual use of RO water won't lead to any problems whatsoever... IF
you are smart enough to manage the nutrients and pH well, and that can be
easily done by using a fertilizer formulation designed for pure water and
with the right nutrients.

For about 5 or 6 years I accomplished that by using Dyna-Gro "Grow" formula
and adjusting the pH by the addition of ProTekt. For the last 28 months, I
have used the GreenCare "Orchid Special" for pure water at the designed rate
of 125 ppm N and my plants couldn't be healthier or happier. (I don't have
the wherewithal to do most of those tests Pat mentioned, so I let the
fertilizer companies take care of them for me.)

If you fail to use the RO water intelligently, Pat is correct about
nutritional issues, brought about by either the lack of nutrients being
present or them being unavailable due to pH issues. That latter case can
also lead to certain ion toxicity too, as they are variably available
depending on the pH, and you can actually poison the plants by unknowingly
putting too much of certain ions in solution.

As far as delivering the nutrient solution, first let me suggest that the
small tank that usually comes with an RO system is of little value, if any.
It is a feeble attempt (for horticultural purposes anyway) to convert it to
an "on-demand" system.

I prefer to think of it in two segments: putting the RO in the storage tank
and not overflowing, and pumping it through the dosing pump and hose to my
plants.

For the first part, I attached a simple float valve to the RO system outlet
in the tank. When it's full and flow is cut off, back-pressure in the RO
system triggers an included upstream pressure cutoff valve so the membrane
does not sit there under pressure at idle. (I'd check to see if your
discount system has one, as it prolongs the membrane life.)

As for delivering the "final product" to your plants, I have tried two ways.
The first was a simple in-line pump. Simple and reliable, I had to turn it
on for watering, not dally too much during the process to avoid overheating,
and sure had to remember to turn it off when I was done. My current setup
uses a well booster pump, complete with an anti-backflush valve, a 20-gallon
bladder tank and pressure switch. This was a 1/2 HP Home Depot
off-the-shelf unit, set up with the input coming from the bottom of the
storage tank and the output running through my dosing pump and onto a hose
(and mister, but that's an aside here).

As long as the hose end (or mister solenoid valve) is closed - I use
spring-loaded squeeze valves before the water wands - it is off. When
either is opened when watering, the bladder tank pushes away, and when its
internal pressure gets low, the pump comes on the repressurize it. Yeah, I
invested about $150, but it's reliable and I don't even have to think about
it.

--

Ray Barkalow - First Rays Orchids - www.firstrays.com
Plants, Supplies, Artwork, Books and Lots of Free Info!


"Pat Brennan" wrote in message
...
Dustin,

Before you switch to RO, what level of alkalinity measured in parts per
million (ppm) of calcium carbonate equivalents (CaCO3) are you planning to
run at and how do you plan to add the alkalinity? Do you understand the
formation of carbolic acid in RO water exposed to air? Do you know how to
do leachate pH tests and have you generated a good tap water leachate
baseline to compare to the values generated after the switch to RO? If
you answered no or don't know to any of these, be very careful. Although
RO can solve all sorts of water problems, it can also make plants very
sick in less than a year. After you make the switch, watch leaf color
very carefully, it will be the first sign you have problems (leachate
tests should identify problems long before they show up in the leaves).

As for the pump systems, $80 seems like a very good price but in the right
ballpark. Northern has a 1/2 horse pump for $40 and a 6 gallon tank for
$35. Add a $10 pressure switch and you are there. You get what you pay
for. A six gallon tank has a .6 gallon drawdown. Start with a full tank,
draw off .6 gallons and on comes the pump. I expect the cheap pump will
not be able to get .6 gallons into the tank while the hose is on so I do
not think the pump cycling on and off will be an issue. But watering will
be like the hose is connected directly to the pump except the pump will
turn off when the hose is turned off. Hey isn't that what you were
looking for?

I expect the system will come set at 20/40 psi which I think is way too
low. A lot of the water breakers, such as the 'red head', do not work
right at 20 psi. The pressure switch has two nuts that allow you to
change these setting. Go slowly and start by only changing the pump kick
in pressure point. 30/50 will be a big improvement but may require that
you add air to the pressure tank. I run at 45/60 which is not possible
with the $40 Northern pump.

I have trashed a couple of the $40 pumps because fine gravel from the
greenhouse floor got into the water storage tank. A filter between the
storage tank and the pump would help. I have not had this problem with
better pumps.

The $80 system will come with a pressure switch. Take it off and replace
it with a pressure switch with low pressure shutoff. They cost less than
$20 and sooner or later it will save the pump by turning the system off
when the storage tank is empty. Neither cheap or expensive pumps like to
be run dry. Cheap one really don't like it.

Pat