NOTES FOR A NUTRIENT RESERVOIR
pH is a state.
EC is a conductivity.
TDS is a factor.
UK English notes on what published sources say a hydroponic pH or EC reading can show — and what that reading still is not.
Source-led notes for growers who keep a reservoir log. WaterMeasure is not a drinking-water laboratory, and this edition publishes no original readings.
WHAT THIS SITE DOES
What is the difference between pH, EC and a TDS ppm?
pH states the acid–base condition of a hydroponic nutrient solution. EC states how well that solution conducts electricity. A TDS ppm on a portable meter is usually EC multiplied by a scale such as 500, 600 or 700, so one solution can print three ppm values. None of these readings names a single nutrient, and none is a drinking-water safety decision. This edition explains published sources and has not published an original series.
| Quantity | What it states | What it does not state |
|---|---|---|
| pH | Acid–base state | Dissolved-salt mass, a named nutrient, or a drinking-water result |
| EC | Electrical conductivity | Which ion produced the current |
| TDS ppm | EC multiplied by a factor | A drinking-water safety decision |
- Science in Hydroponics, EC to ppm chart ↗
- WHO, total dissolved solids background document ↗
- Drinking Water Inspectorate, standards and regulations ↗
What has this edition published, and what has it left out?
WaterMeasure publishes UK English notes on horticultural nutrient solutions, and three blank CSV files for later records. The notes cite Science in Hydroponics, the World Health Organization, the Drinking Water Inspectorate and a Thermo Fisher pH handbook. Those measurements stay with their authors. Pool, aquarium and food methods are outside this edition. No original pH or EC series by this publication is included.
Nutrient notes
pH, EC, the TDS factor, ATC and immersion — each kept in its own column.
Open the nutrient notes ↗02 / THE DISTINCTIONSource notes only
This edition explains published sources. Calculations and original series stay off the site.
Read the methods ↗03 / THE RELATIONSHIPRelated retail shops
hmdigitalp.co.uk and smartquali.co.uk are commercially related. The other shops are named on the disclosure page.
Read the disclosure ↗START WITH THESE NOTES
Which four notes keep those columns apart?
The four notes below separate pH from EC, a TDS factor from conductivity, ATC from the sample’s own chemistry, and a handheld dip from continuous immersion. Each one is a source-based note. Open a note for the cited experiment, the limit of that citation, and the blank record that would have to be filled before an original series could be claimed.
Source-based noteWhat pH and EC tell you in a nutrient solution
pH is an acid–base state. EC is a conductivity. Published hydroponic experiments keep those two readings apart, and they do not name individual nutrients.
8 MIN READ ↗
Source-based noteTDS on a meter is EC times a factor
Portable meters usually display ppm as conductivity multiplied by 500, 600 or 700. That number is not a drinking-water safety decision.
7 MIN READ ↗
Source-based noteWhat ATC corrects — and what temperature still changes
Automatic temperature compensation adjusts an electrode slope or a conductivity coefficient. It does not turn the sample into its chemistry at 25 °C.
7 MIN READ ↗
Source-based noteHandheld dips and continuous immersion are different jobs
A waterproof handheld probe is not automatically a probe that the maker allows to stay in the tank. Handbooks for the related retail models have not been checked.
7 MIN READ ↗READ THE CLAIM. SEE THE SOURCE.
Why can two TDS ppm readings disagree on the same solution?
A displayed ppm is still only a factor times conductivity. pH, EC and that scale are three different numbers, and two meters can disagree while measuring the same tank. This edition publishes the explanation and a blank record. It does not publish original repeats, and it does not convert a nutrient-tank ppm into a drinking-water result.