Water source selection

Hydroponics is unforgiving about water chemistry. Your source water sets the baseline everything else builds on — get it wrong and you fight it every single day. Measure before you mix.

Measure your baseline EC first

Before your first grow, measure your tap water's EC with a meter or test strip. If EC > 0.5 mS/cm or you have hard water, consider an RO (reverse osmosis) filter. High baseline EC means you have less headroom to add nutrients before you hit the plant's limit.

Tap vs RO vs rainwater

• Tap — convenient, but often high in carbonate hardness that fights your pH adjustments. Fine for many crops if the baseline EC is low.
• RO — a near-blank slate you build up deliberately. Best for demanding crops and hard-water areas. If using an RO system, check that your water pressure is 45–60 PSI.
• Rainwater — soft and low-EC, but variable and needs storage and filtration.

Carbonate hardness matters

Hard water resists pH changes (high buffering capacity). You will use more pH Down and still see pH creep back up. If your water is hard, RO or a blend is often less frustrating than fighting it daily.

pH management fundamentals

Use phosphoric acid as pH Down — never baking soda or lye. Adjust in small steps and let the reading settle. See Calibrating pH and EC probes so your readings are trustworthy in the first place.

EC interpretation

Rising EC usually means water evaporated and left nutrients behind — top off with plain water. Dropping EC means the plants are feeding. Always work in mS/cm, never PPM.