Your Source Water Is the First Ingredient in Every Recipe
Two farms run the same crop, the same system, the same fertiliser brand. One hits target yields and the other fights deficiencies all season. Very often the difference is not the recipe — it is the water the recipe was dissolved in.
Municipal, well, river and rainwater each arrive with their own mineral load, alkalinity and pH. A standard formulation assumes reasonably clean water; anything else needs the recipe rebuilt around your analysis, or the water treated. This guide covers what to test, how to read the numbers, the adjustment logic, and what to send your supplier so they can build the recipe properly.
What to Test, and What Each Number Does
| Parameter | Why it matters | Trouble threshold (indicative) |
|---|---|---|
| EC / TDS | Fills part of your target EC before you add any fertiliser | Above about 0.4–0.5 mS/cm needs accounting for |
| pH | Sets your acid demand and affects micronutrient availability | Above 7.5 usually needs continuous acid dosing |
| Alkalinity (as CaCO₃) | Buffering capacity; drives acid consumption and pH stability | Above 150–200 mg/L needs pre-treatment or heavy acid use |
| Calcium and magnesium | Count toward the crop’s supply and affect the Ca:Mg:K balance | High Ca with high alkalinity causes precipitation risk |
| Sodium | Not a nutrient; accumulates and competes with potassium | Above roughly 50 mg/L is a concern in recirculation |
| Chloride | Toxic at modest levels for many crops; accumulates in loops | Above 100 mg/L warrants action for sensitive crops |
| Sulphate | Contributes EC and sulphur; accumulates in recirculation | High levels crowd out the recipe’s nutrient budget |
| Boron, iron, manganese, zinc | Can be useful or toxic depending on level | Micronutrient panels matter more than growers expect |
| Bicarbonate (HCO₃) | Raises pH continuously; the classic hard-water problem | Drives ongoing acid demand in recirculating systems |
Alkalinity: The Number That Decides Your Acid Bill
pH tells you where the water is now. Alkalinity tells you how hard it will fight you. High-alkalinity water resists every acid dose, and the grower ends up chasing pH daily with large acid volumes and unstable results.
- Neutralising alkalinity is standard practice: dose acid to a target pH, allow contact time, then aerate or agitate to release CO₂ before use
- Acid choice matters. Phosphoric adds phosphorus to the balance; nitric adds nitrogen; sulphuric adds sulphur. Pick the one that fits what your recipe is short of rather than what is cheapest per litre
- Do not neutralise in the mixing tank with fertiliser already added — precipitation risk is highest when concentrated A-tank calcium meets sulphates or phosphates at high pH
- Recalculate after treatment. Neutralised water has a different EC and a different ion balance; the recipe must be built on the treated analysis, not the raw one
Building the Recipe Around the Water
| Step | Action |
|---|---|
| 1. Establish the baseline | Start from the treated water EC and its calcium, magnesium, sulphate and micronutrient content |
| 2. Set the target | Define crop, growth stage and target EC; the water’s contribution counts toward it |
| 3. Subtract the water | Remove what the water already supplies from the formulation before adding fertiliser salts |
| 4. Correct the ratio | Adjust Ca:Mg:K and the N form (nitrate vs ammonium) for the season and root-zone temperature |
| 5. Check precipitation | Verify calcium against sulphate and phosphate at your working pH and concentration |
| 6. Validate in the field | Run the recipe, then send a solution sample for analysis after two weeks and correct |
A common practical case: water supplying 80 mg/L calcium and 20 mg/L magnesium already covers a meaningful share of a leafy green crop’s demand. If the recipe ignores it, calcium and magnesium overshoot, potassium uptake suffers, and the grower sees a problem that looks like a potassium deficiency but is actually a ratio issue.
When to Treat, When to Adjust
| Situation | Best response |
|---|---|
| EC under about 0.3 mS/cm, low alkalinity | No treatment; build the recipe directly on the analysis |
| Moderate alkalinity, low sodium | Acid neutralisation plus a recipe adjustment |
| High EC, high sodium and chloride | Reverse osmosis, then blend back a controlled fraction for stability |
| Surface or river water | Filtration plus disinfection as a minimum; treat as a biological risk |
| Rainwater harvest | Excellent starting point; add filtration, first-flush diversion and disinfection |
| Variable municipal supply | Seasonal re-testing; buffer tank with treatment downstream |
Sampling: Getting a Report You Can Trust
- Sample at the point of use, not at the meter — well head and tank outlet can differ substantially
- Run the tap or pump for several minutes before sampling
- Use a clean bottle; for micronutrient panels, ask the lab whether a preserved bottle is required
- Sample seasonally: groundwater and municipal sources move, and a single test may not represent August
- Request results in mg/L (ppm) and mmol/L or meq/L so the recipe maths is straightforward
- Re-test after any treatment change, and after any significant change in yield or water chemistry
What to Send Your Supplier
- Full water analysis with date, source and units clearly stated
- Crop, cultivar, growth stage and target EC and pH
- System type and whether the loop recirculates
- Treatment already installed (RO, UV, ozone, acid dosing) and the treated-water analysis if available
- Climate data: typical root-zone temperature range, peak VPD, and whether the house is heated
- Any known constraints: discharge limits, tank sizes, dosing equipment capabilities
With those six items, a competent supplier can return a working recipe and a stock solution plan rather than a generic chart. Pair this with our A and B tank mixing guide and the RO, UV and ozone treatment guide to complete the water side of the design.
FAQ
What water quality is best for hydroponics?
Rainwater or reverse-osmosis permeate gives the cleanest starting point, typically under 0.1 mS/cm with low alkalinity. Many farms run perfectly well on municipal water up to about 0.4–0.5 mS/cm once the recipe is adjusted for it.
Do I need RO for a commercial hydroponic farm?
Not automatically. If sodium and chloride are low and alkalinity is manageable with acid dosing, adjusting the recipe is cheaper than running an RO plant. RO becomes worthwhile when sodium, chloride or total EC are high enough to force frequent dumping in a recirculating system.
Why does my pH keep rising after I set it?
Alkalinity, usually bicarbonate. Each acid dose neutralises part of the buffer and releases CO₂, so pH climbs again. Neutralise before adding fertiliser, allow contact time, and aerate before use.
Can I use well water for hydroponics?
Frequently yes, but test first. Wells commonly carry high alkalinity, iron, manganese, and sometimes sodium or chloride. Iron and manganese need oxidation and filtration; the rest is handled by treatment plus recipe adjustment.
How often should I re-test my water?
At commissioning, then seasonally for the first year, and after any change in source, treatment or yield pattern. Municipal supplies also change disinfectant and source blend between seasons.
Does hard water change my fertiliser recipe?
Yes. Calcium, magnesium and sulphate in the water already count toward the crop’s supply. Subtract them from the formulation before adding salts, then correct the ratio to your crop target.
Get Your Recipe Built on Your Water, Not a Generic Chart
Send your water analysis, crop plan and system details through the quote form. We will return a treatment recommendation, a crop-specific recipe starting point, stock solution concentrations and a monitoring schedule matched to your source water.