Water, pH & EC

Can I use tap water, or do I need reverse osmosis water?

GrowDealz team · Updated

Short answer

Tap water is fine if it's moderately hard (EC below roughly 0.8). RO water is a blank slate for exact control, but you must add Cal-Mag.

Measure your tap EC first with an EC meter. If it's above roughly 0.8–1.0, a big part of your feed budget is already used up by minerals, and a mix of tap and RO or full RO makes sense. Chlorine mostly leaves if you let the water stand 24 h, but chloramine doesn't, so ask your supplier which one you have.

RO water has next to no calcium and magnesium, so add Cal-Mag, or use a feed made for soft water. Find them in our nutrients.

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