Measure source water before adding nutrients
Take a sample from the supply you will use to fill the tank. If it passes through a filter, measure it after filtration. Record the date, pH, EC and temperature. You can compare these readings with the finished solution and the next batch of water.
High starting EC makes a single nutrient reading harder to interpret because some conductivity comes from source-water salts. Low EC does not prove that the water supplies enough calcium or is suitable for an edible crop. An unfamiliar supply needs testing.
pH, hardness and alkalinity mean different things
| Measurement | What it describes | Why it matters |
|---|---|---|
| pH | Current acidity | Preparing and monitoring the solution |
| Hardness | Mainly calcium and magnesium content | Estimating the nutrient contribution from water |
| Alkalinity | Capacity to neutralize acid | Understanding acid demand and recurring pH rise |
| EC | Combined conductivity of dissolved ions | Accounting for the starting salt background |
Two samples with the same pH can have different alkalinity. A small amount of adjuster may change one noticeably while the other resists the change. A pH meter does not measure that reserve. Hardness and alkalinity can be related, but read them as separate results in a report.
What to request in a water test
Ask for alkalinity, calcium, magnesium, sodium, chloride and conductivity. Check the units: alkalinity is often expressed as CaCO3, while individual elements are reported in mg/L. Values expressed on different bases cannot simply be added together.
A water supplier report helps describe the usual supply but may not represent the sample at your tap. A laboratory sample is more useful for a well or a supply that changes with the season. Ask about the sampling container and procedure before collecting it.
What filters change
A sediment filter catches particles but usually leaves dissolved salts in the water. A carbon filter is not a substitute for mineral analysis either. A household sodium ion-exchange softener can reduce hardness while raising sodium; softened water is not automatically better for hydroponics.
Reverse osmosis reduces many dissolved salts. Results depend on the equipment and its maintenance, so test water after the filter. When switching to water with fewer minerals, review the whole recipe, including calcium and magnesium.
Compare supplies in a small batch
Prepare separate small samples using the same complete fertilizer and dose per litre. Record the starting readings, final EC and pH behaviour after mixing. This compares ease of preparation; it does not replace testing for unidentified salts or water quality.
Blending tap water with reverse-osmosis water can reduce starting mineral content. Record the proportions and blend the water before adding fertilizer. Do not calculate an acid dose from the blend ratio alone: measure the finished solution and follow the adjuster instructions.
When pH keeps rising
- Check the pH meter in fresh buffer.
- Record top-up volumes and source-water composition.
- Test alkalinity if the water history is unknown.
- Review the complete recipe and mixing order.
- Prepare a new trial batch when changing water supplies.
Repeatedly alternating pH-down and pH-up adds substances to the tank. If the adjustment history has become unclear, replacing it with a known solution gives the next observation a usable starting point.