Apax Lab TDS Meter (new model) – Measure the Mineral Content of Your Coffee Water
The probe goes in, the display settles, and after a quiet moment there is a number where there used to be a guess. The water that is about to run through your coffee reveals how much mineral is dissolved in it. “Should be about right” becomes “this is it”.
What the device measures
Water is never just water, but a solution of H₂O and dissolved minerals such as magnesium, calcium and bicarbonate. Pure H₂O barely conducts electricity; the more minerals are dissolved in it, the more conductive it becomes. The Apax Lab TDS Meter measures exactly this conductivity and estimates the total dissolved solids from it – shown in PPM, parts per million.
Which individual minerals sit in the water is not something the device shows; it gives you the one number you can orient yourself by, day after day. And that counts: with too little mineral content, coffee often comes across as flat, because the water lacks the partners it needs to dissolve and carry aroma. With too much mineral content, the mineral impression settles over the finer notes. In between lies the range where body and clarity come together. Where exactly your optimum lies is also a matter of taste – there are no water laws and no water police, and our observation is one of many.
At a glance
| Brand | Apax Lab, Australia |
| Measuring principle | electrical conductivity, estimated TDS derived from it |
| Display | digital readout in PPM, with HOLD button |
| x10 symbol | when it flashes, multiply the displayed value by ten |
| Measuring temperature | around 25 °C |
| Immersion depth | 5 cm maximum |
| Measuring time | 10 to 30 seconds until the reading is stable |
| Operation | ON/OFF button, HOLD button, removable protective cap |
| Not suitable for | hot water |
How you go about it
Cap off, press ON/OFF – the display reads 000. Then hold the probe no deeper than five centimetres in water at around 25 degrees and let the value settle for 10 to 30 seconds. Once it holds still, the HOLD button keeps it on screen while you lift the device out of the water. Afterwards shake off the water or dab the probe dry with a clean tissue and put the protective cap back on. The device does not belong in hot water.
In everyday use that means: check your base water first – distilled or reverse-osmosis water sits close to zero. Then you mix your water to a recipe, measure, and know what you are brewing on. If the value is off, you adjust next time, and because the result is a number, it repeats exactly the next day. It is also how you check the mineral concentrates from our Apax Lab Collection such as Tonik, Jamm, Lylac and Konflux. As the importer of Apax Lab in Switzerland, we supply original goods. How to build your coffee water from scratch is laid out step by step on our page Composing Your Own Coffee Water.
Who it is made for
For everyone who would rather see their brew water than guess at it – whether you work with Apax Lab profiles, look for the same results day after day, or simply want to understand what is happening in your cup. And for everyone whose tap water shifts with the seasons and who wants quick certainty before brewing. Nobody needs this device to make good coffee. You want it – or you do not, and both are fine.
The setup that fits
Water and scale belong together: if you want coffee scales that are affordable and precise, the Normcore Collection is the right place. If you want an app, a flow-rate display and Bluetooth, take a look at the Acaia coffee scales. When it comes to the water in a plumbed-in machine, the filter solutions in the Brita Collection are worth a look, and everything around tampers, puck screens and WDT is in the Barista Tools. How hardness and alkalinity shape extraction is something you can play through beforehand in the Water Chemistry Simulator.
Frequently asked questions
Does the TDS Meter also measure the espresso in the cup?
No. Through conductivity it measures the minerals dissolved in the water, that is the TDS of your brew water. For the dissolved coffee solids in the finished espresso you need a refractometer – that works with light refraction and is a different tool.
Which mineral content suits coffee?
We work with an ideal range of roughly 50 to 100 mg/l, tending towards the upper end for espresso and below it for filter. That is a guideline and a matter of taste at once – our recommendation is one of many.
Why does “x10” flash on the display?
Then you multiply the displayed value by ten. With ready-mixed coffee water you will rarely see it, with heavily mineralised water more often.
Can I measure hot water straight from the kettle?
No, the device is not made for that. The manufacturer states around 25 °C as the measuring temperature – so let the water cool down, or measure before you heat it.
Can I see the TDS Meter in person before buying?
Yes, in our showrooms in Bern, Gerberngasse 44 and Zurich, Hagenholzstrasse 50b. Delivery takes 2 to 4 business days throughout Switzerland and to Liechtenstein.
Roastery tip
As a coffee roastery we see water as part of the recipe, not as a side note – it makes up over 90 percent of the drink. Measure that foundation once, then brew a full-bodied roast like Cozy Chocolate or Nutty Delight and you will often taste the difference more clearly. For maximum body without any acidity there is Very Nutty, and for a fruity experience Wild Peach is worth it. That is our recommendation, one of many.
