High pH - Hard Water Hydroponics

by Jon J.
(Prescott Valley, AZ)

My well water has a pH of 8.2. I have tried lowering the pH so I can use it for hydroponics, but it bounces back (less than 24 hours). In reading, it seems that would be caused by hard water. The million dollar question is how do I correct my waters pH. Jon

Answer: Jon- the main culprit for hard water is Calcium Carbonate. In small amounts, the pH of the water will only need a small adjustment. The ideal pH of the water you start with would be 7.0. After adding hydroponic nutrients and additives, the ideal pH of the solution should be around 5.9-6.2.

Having Calcium Carbonate in your water will cause more of a problem than just having your pH out of whack. Calcium Carbonate will register on your TDS or EC meter, and the more Calcium Carbonate in the water, the less room there will be for your nutrients. On top of this, the pH down that you add to correct the problem also increases the TDS/EC of the solution (leaving even less room for your nutrients). Finally, plants tend to uptake the Calcium Carbonate before they will uptake other forms of Calcium which are more usable to the plants. If you grow in water with high levels of Calcium Carbonate, there is a very good chance your plants will exhibit a Calcium deficiency (or other nutrient deficiency).

The farther your water is from a pH of 7.0, the less desirable it is to use for hydroponics. If the TDS of your tap water is over 150, there is reason for concern. If the pH of your tap water is over 7.5, I would not even consider using it. I have made this mistake before, and in hindsight I wish I had paid the extra cash and bought bottled water. You can use either spring water or distilled water....in bottled form both should be OK.

The only other option would be to use a reverse osmosis filter with your well water, which would reduce the ppm of your water to nearly zero. The removal of Carbonates (and Sulfur, Iron, and Sodium) from your water will also drop the pH substantially (possibly down to 7.0). The only drawback with a reverse osmosis system is the initial cost of the system, which can be a little expensive. If you decide to go this route, I recommend a 3 stage reverse osmosis filter for the best results. I hope this helps Jon, and Happy Growing!