Pros and Cons of RO Water for Gardening


By now, readers of this site will already understand osmosis and reverse osmosis. So, good or not? RO water for gardening…?  Let’s get a refresher of the definitions down first.

Osmosis: A process by which molecules of a solvent (liquid) tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membrane. Like a plant “consuming” water.

Reverse Osmosis (RO): A process by which a solvent (a liquid) passes through a porous membrane in the direction opposite to that for natural osmosis when subjected to a hydrostatic pressure greater than the osmotic pressure.

In water treatment, RO is a process that removes the contaminants in the water by utilizing pressure to FORCE the water molecules through a membrane and cleaning/flushing/trapping the contaminants in the membrane and filters.  This leaves pure, delicious drinking water.

As we’ll find out below, RO water is not only good for drinking by humans, but can also do your flower or vegetable garden very well, as well.

How Can RO Water Help with Gardening?

By starting with RO water in your garden, you’re starting on an even playing field…homeostasis of water, if you will.  RO water is free of contaminants so your water impact on the growth of your flowers and vegetables is more measurable because the water quality is constant.

Sometimes, contaminants in water such as iron, manganese, calcium, magnesium, and chlorine can interfere with nutrients in fertilizer, potting soil, etc., and cause problems.

Growing Without Contaminants is Better for You and the Plants AS LONG AS YOU ARE PAYING ATTENTION!

By starting with this kind of purified water it allows you, the grower, to add nutrients at his or her discretion and/or as needed.  This is how the RO water can make growing and watering effectiveness more measurable.  This way, the only nutrients that are being added to the water (after the RO process) are those that are beneficial to the plants.

ro for gardening irrigation system

Purchasing Tips 

For our most comprehensive Reverse Osmosis System purchasing guide, you should go to this page.   

However, here are some of the highlights:

  • Cost Considerations
  • Capacity
  • Maintenance
  • Waste (this is in regards to the amount of “regular” water that is needed to create RO water. On average, 4 gallons of tap or rainwater will produce 1 gallon of RO water.

Important Note:  RO water is corrosive so it can do a number on metal piping.  It should never be used in conjunction with copper or galvanized piping.  ALL the RO systems we recommend are built with components that are resistant to this corrosion.

A Note About Capacity and Money

Size and capacity are not the same things.  Size means the amount of physical space a certain RO system takes up. Capacity, on the other hand, is how MUCH and how FAST a reverse osmosis system can produce RO water. Most RO systems will be able to produce from 15 to 50 gallons per day (GPD).  Check here for current prices on Amazon for different RO machines or check our comparison chart.

Commercial and industrial RO systems escalate in price rapidly, but with the higher price tag so does the capacity increase. Check this beast out! But, there’s a catch! If you’re producing a large amount of RO water per day, say 50 gallons and above, then you’ll need to address storage needs.  So, that can add to the already high price.

Bottom Line:

Even novice gardeners like my family and I can benefit from the use of ANY type of water treatment system.  Obviously, we are all in favor of and use RO water for our gardens and flowers.  The removal of the contaminants from the RO process will GREATLY benefit the plants, though, and that’s what really matters!

RO water for gardening will reduce root rot issues like Pythium and other fungal diseases that can be created by waterborne bacteria in untreated/unfiltered water.

So, while a reverse osmosis system for your gardening may have a STEEP initial investment, don’t forget that you can also use it to cook and as regular drinking water in the house.  In the end, that investment will pay off.