Water Sources for Greenhouse Production: Well Water, City Water & Reverse Osmosis

Why Water Quality Matters in Greenhouse Production

Obviously water is the cor of a "Hydro"ponic business. Mineral content, pH, and EC influece fertilizer programs and crop management and final crop performance. 

The Three Main Water Sources

1. Well Water

Well water is drawn from underground aquifers and is the most common in rural greenhouse operations. Its quality varies significantly by region and geology.

Typical characteristics:

• High mineral content — calcium, magnesium, iron, and bicarbonates can be an issue
• EC are variable and can range from 0.5–2.0+ mS/cm 
• pH typically 7.0–8.5 — often alkaline due to dissolved carbonates
• May contain iron or manganese that can clog drip emitters etc

Key considerations:

• Test well water regularly through the season
• High bicarbonate levels require acid injection (phosphoric or nitric acid) to bring pH into the 5.5–6.2 target range
• Pre-existing calcium and magnesium must be factored in to fertilizer formulations
• High Iron levels can be aan issue

2. City Water

Municipal water is treated for human consumption and is generally more consistent than well water, but has its own challenges

Typical characteristics:

• EC typically 0.2–0.8 mS/cm — lower mineral load than most well water
• pH usually 6.5–8.0
• Contains chlorine or chloramine as disinfectants
• Sodium and fluoride may be present

Key considerations:

• Chlorine dissipates quickly with aeration or UV exposure; chloramine does not and requires activated carbon filtration or ascorbic acid treatment
• Sodium accumulation over time can raise substrate EC and cause osmotic stress — monitor regularly
• Municipal water quality reports are publicly available and provide a useful baseline, but test your own supply for accuracy
• Generally more predictable than well water, making nutrient program management easier

3. Reverse Osmosis (RO) Water

Reverse osmosis systems force water through a semi-permeable membrane, removing 95–99% of dissolved minerals, salts, and contaminants. RO water gives growers the highest level of control over their nutrient program.

Typical characteristics:

• EC near zero (0.01–0.05 mS/cm) 
• pH typically 6.0–7.0 after treatment
• No chlorine  etc

Key considerations:

• Provides maximum precision — your nutrient formula is the only source of minerals,
• Ideal for sensitive crops (lettuce, basil, microgreens) and operations with problematic source water
• RO systems produce wastewater - typically 3–4 gallons rejected per gallon produced
• Membranes require regular maintenance and replacement
• Higher upfront cost

Quick Comparison

Summary

No matter your water source, the first step  to get a baseline test for pH, EC , alkalinity etc Growers using RO water have the most flexibility; those using well or city water need to account for existing minerals and pH management as part of their standard program.

Contact the Paramount Seeds team — we’re happy to help with crop-specific guidance.

Disclaimer: Paramount Seeds is a seed supplier only. We do not sell, supply, or endorse any water treatment equipment, filtration systems, fertilizers, or nutrient products. The information in this article is for general educational purposes. Water quality varies significantly by location — always test your specific water supply and consult a qualified agronomist or irrigation specialist before making changes to your water treatment or nutrient program.