Water pH, Alkalinity and Hardness

Your water's pH doesn't tell you how much pH down your feed will need. Alkalinity does. Two waters can start at the same pH and take very different amounts of RunClean to hit target. You don't need a water report for a normal batch: mix A and B at chart rate, then measure and adjust the finished feed. If your tap is about 250 ppm (0.5 EC on the 500 scale) or lower, run it straight. Above that, blend in RO to bring it to about 250 ppm.

Three different measurements

• pH is how acidic or alkaline the water is at the moment you measure it.
• Alkalinity is how much acid the water can absorb before the pH moves, mostly from bicarbonates and carbonates. This is what sets your pH down use.
• Hardness is the dissolved calcium and magnesium.

Your nutrient meter doesn't measure any of these. A 150 ppm reading (on either the 500 or 700 scale) is an estimate of total dissolved salts from conductivity, not 150 ppm alkalinity. A water report lists alkalinity separately, usually as mg/L or ppm as CaCO₃.

Mix first, then adjust the finished feed

1. Dissolve Part A, then Part B, separately, at the chart rate.
2. Measure the finished pH and EC.
3. If it needs pH down, use RunClean in place of pH down: add it a little at a time, mixing and rechecking, until you reach target pH. It's a strong acid (about pH 1), so small additions go a long way.
4. If it doesn't need pH down, add 0.2–0.4 mL of RunClean per gallon as a descaler, then check pH again.

If you need pH up, any potassium carbonate works. Keep concentrated RunClean, bleach and pH up in separate containers and add them to the feed separately. Concentrated bleach and RunClean can release chlorine gas.

Hard, alkaline water is also what leaves white scale in lines and emitters. If you use RunClean, you won't have scale. See what RunClean does.

Tap, RO or a blend

All three work. The 250 ppm rule covers most cases: tap around 500 ppm (500 scale) blends about 50/50 with RO. We like enough tap in the blend to cut down or eliminate pH up.

The minerals in your water don't replace Part A or Part B. Keep the recipe the same. Straight RO doesn't create a need for Cal-Mag either; our Veg and Bloom use multiple sources of calcium. More in tap water, RO or a blend.

When a water report helps

If the same recipe suddenly needs a lot more acid, check whether your water source or RO blend changed. For a problem that won't go away, a water analysis shows alkalinity, hardness, sodium and other minerals, and tells you whether that source needs a different blend or treatment.

Lowering pH doesn't remove dissolved salts. After you change the water or blend, mix the same complete recipe and check the finished feed. If you run injectors, compare their output with a hand-weighed batch made from the same water instead of changing the feed strength to chase an old EC number.