# Do I really need to pH my water?

> In coco, rockwool and hydro, yes: adjust every batch to about pH 5.5-6.2 in hydro or 5.8-6.3 in coco, because these media barely buffer pH. In bagged soil, adjusting to pH 6.2-6.8 is good practice but the mix buffers small errors, and your water's alkalinity matters more than its pH. In living soil, generally no. The accepted ranges are soil 6.0-7.0 and soilless 5.5-6.5.

- Canonical: https://genetixbay.com/knowledge/answers/do-i-need-to-ph-my-water.html
- Topic: pH and EC · Type: How-to
- Evidence: Established · Status: Draft: awaiting expert review
- Full article: [pH and nutrient availability: what pH really controls, by medium](https://genetixbay.com/knowledge/ph-ec/ph-nutrient-availability.md)
- Also asked as: Do I need to pH my water? | What happens if I don't pH my water? | Is pH necessary in soil? | Do I need to pH water for living soil? | Can I skip pH in coco?
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Short answer

In [coco](https://genetixbay.com/knowledge/glossary/coco-coir.md), [rockwool](https://genetixbay.com/knowledge/glossary/rockwool.md) and hydro, yes, every batch: about [pH](https://genetixbay.com/knowledge/glossary/ph.md) 5.5–6.2 in hydro and 5.8–6.3 in coco. In [bagged soil](https://genetixbay.com/knowledge/glossary/potting-mix.md) it's good practice (pH 6.2–6.8), but the mix forgives small errors and your water's [alkalinity](https://genetixbay.com/knowledge/glossary/alkalinity.md) matters more than its pH. In [living soil](https://genetixbay.com/knowledge/glossary/living-soil.md), generally no. The ranges, soil 6.0–7.0 and [soilless](https://genetixbay.com/knowledge/glossary/soilless.md) 5.5–6.5, are broadly agreed accepted practice. *Established.*

## Why

pH sets how soluble each nutrient is. Above about 6.5 in soilless media, iron, [manganese](https://genetixbay.com/knowledge/glossary/manganese.md), zinc and [boron](https://genetixbay.com/knowledge/glossary/boron.md) drop out and phosphorus precipitates with calcium [1][3]. Below about 5.3, iron and manganese can reach toxic levels while calcium and magnesium fall [3].

Soilless media have little buffer. Hydro has none. Whatever pH you pour is close to what the roots get, so it must be right each time [2].

Soil buffers. Peat, compost and lime absorb small pH errors for weeks. The slow threat is alkalinity: bicarbonate in [hard water](https://genetixbay.com/knowledge/glossary/general-hardness.md) acts like adding lime at every watering and pushes root-zone pH up over a grow, whatever the water's pH reads [1].

Drift within the range is normal. Aim for a band, not one perfect number.

## The numbers

| Medium | Adjust water? | Target |
|---|---|---|
| [DWC](https://genetixbay.com/knowledge/glossary/dwc.md), [RDWC](https://genetixbay.com/knowledge/glossary/rdwc.md), [NFT](https://genetixbay.com/knowledge/glossary/nft.md) | Every batch | 5.5–6.2 |
| Coco, rockwool | Every batch | Feed 5.8–6.3, [runoff](https://genetixbay.com/knowledge/glossary/runoff.md) 5.8–6.5 |
| Bagged soil, bottled feed | Recommended | 6.2–6.8 |
| Living soil | Generally no | [Root zone](https://genetixbay.com/knowledge/glossary/root-zone.md) ~6.3–7.0 |
| Any medium, water alkalinity | Treat if high | Act above 100–150 mg/L as CaCO₃ |

## What to do

1. Calibrate your [pH meter](https://genetixbay.com/knowledge/glossary/ph-meter.md) with pH 7 and pH 4 buffers.
2. Hydro and coco: add nutrients, then adjust pH, every batch.
3. Soil: adjust to 6.2–6.8 and check runoff monthly.
4. Get a water report; acidify if alkalinity is high.
5. Living soil: dechlorinate and leave pH alone.

*Safety:* pH down is a concentrated acid. Gloves and eye protection; add acid to water.

## Common mistakes

- Skipping pH in coco "because soil doesn't need it".
- Chasing exactly 5.8 several times a day.
- pH-ing plain water before adding nutrients.
- Ignoring alkalinity.

## Related

- Full article: [pH and nutrient availability](https://genetixbay.com/knowledge/ph-ec/ph-nutrient-availability.md)
- Answers: [how to adjust pH](https://genetixbay.com/knowledge/answers/how-to-adjust-ph.md) · [pH before or after nutrients](https://genetixbay.com/knowledge/answers/ph-before-or-after-nutrients.md) · [fix soil pH](https://genetixbay.com/knowledge/answers/fix-soil-ph.md)
- Articles: [water quality](https://genetixbay.com/knowledge/ph-ec/water-quality.md)
- Terms: [pH](https://genetixbay.com/knowledge/glossary/ph.md) · [alkalinity](https://genetixbay.com/knowledge/glossary/alkalinity.md)

## Follow-up questions

**What happens if I don't pH my water in hydro?** If you don't pH-adjust in hydro, the solution usually sits well above 6.5 after nutrients go in with alkaline tap water and climbs further as plants take up nitrate. Above about 6.5 in soilless systems, iron, manganese, zinc and boron become less available and new growth yellows between the veins. Hydro has no buffer, so pH every batch.

**Do I need to pH water for soil?** In bagged potting soil, pH-adjusting water to about 6.2-6.8 is cheap insurance but not critical every time, because peat, compost and lime in the mix buffer small errors for weeks. What matters more is alkalinity: hard, bicarbonate-rich tap water pushes soil pH up over a grow. Check runoff or pour-through pH monthly to see the trend.

**Do I need to pH water for living soil?** You generally do not need to pH-adjust water for living soil. Its organic matter and carbonates buffer the root zone near neutral, about pH 6.3-7.0, and microbes work best when left alone. Use dechlorinated water as it comes unless it is very alkaline. Adjusting to pH 6.0 out of habit is a common mistake.

## Sources

1. Lopez RG, Mickelbart MV, Pasian C. Alkalinity management in soilless substrates. Purdue Extension HO-242-W. https://www.extension.purdue.edu/extmedia/HO/HO-242-W.pdf
2. Michigan State University Extension. pH and EC issues still a problem in some greenhouses. https://www.canr.msu.edu/news/ph_and_ec_issues_still_a_problem_in_some_greenhouses
3. Marschner P (ed.), 2012. Marschner's Mineral Nutrition of Higher Plants, 3rd ed. Academic Press. https://doi.org/10.1016/C2009-0-63043-9