TDS Measurement – FAQ

1. What is TDS and why does it matter?

TDS stands for Total Dissolved Solids – it’s a way of expressing how much dissolved material (like minerals) is in the water. Measuring TDS helps us understand whether the system is delivering the expected amount of minerals and whether the RO (reverse osmosis) purification is working correctly.

2. Do I need to measure TDS regularly with my Bluewater system?

No. Under normal operation, you do not need to measure TDS regularly. The system is designed to deliver stable, mineralized water automatically. TDS checks are only needed if Bluewater Support explicitly asks you to take readings for troubleshooting or verification. If you are experiencing any unpleasant or surprising flavor of your coffee, make sure the system is operating normally before getting into TDS measuring. 

3. When will Bluewater ask me to measure TDS?

We typically ask for TDS measurements when:

• You suspect a taste / mineralization issue.

• We want to confirm that the dosing pump and RO purifier are performing correctly.

• We need to compare your meter’s readings against our internal reference.

4. What equipment do I need to measure TDS?

You will need:

• A TDS meter—we recommend a high-quality meter. Very cheap pen-style meters are often less sensitive and may under-read the true TDS level.

• A clean container (e.g., a clean 1 L bottle, glass, or jug).

• Access to your Bluewater faucet or directly to the Bluewater pressureless tank outlet.

5. My meter mentions a “conversion factor” – what does that mean?

TDS meters convert an electrical conductivity reading into a TDS value using a conversion factor, typically 0.5 or 0.7:

• If your meter uses 0.7 – you can read the value as-is.

• If your meter uses 0.5 – multiply the reading by 1.4 to compare it with Bluewater’s internal reference values (which use 0.7).

6. Where should I take the water sample from?

Always sample cold water:

• Take the sample from the Bluewater faucet or directly from the Bluewater pressureless tank.

• Do not take water from a heated tank or espresso boiler, cool it down, and then measure—heating changes the reading and makes the result unreliable.

7. How do I measure TDS step-by-step?

1. Flush the line

   • Open the Bluewater faucet and let about 1 liter of water run to drain.

   • This clears any standing water in the line.

2. Collect the sample

   • After flushing, fill a clean 1 L container with water from the Bluewater faucet.

3. Prepare the meter

   • Turn on the TDS meter and make sure it’s in TDS mode.

   • Rinse the probe with a little sample water, then shake off the excess.

4. Take the reading

   • Place the probe into the sample so the sensor is fully submerged.

   • Wait a few seconds until the reading stabilizes, then note the TDS value (ppm / mg/L).

5. Optional—repeat once

   • Take a second reading from a fresh sample to confirm consistency.

8. I changed the mineral dosing, do I need to measure again?

If you change the mineral dosing setting (for example, from 2.0 ml/L to 3.0 ml/L):

1. Adjust the dosing in your Bluewater system/app.

2. Flush about 1 liter from the Bluewater faucet and discard it.

3. Take a new sample and measure TDS as described above.

Note: The Bluewater faucet reflects the new dosing immediately. Espresso machine internal boilers may take longer to fully reflect new mineral levels, but for TDS measurements, you should always measure at the Bluewater faucet.

9. Why is my TDS reading lower than the numbers you mention?

Different TDS meters have different sensitivities, especially cheaper models. In our lab we see that low-cost meters often read significantly lower than our high-quality reference meter.

That’s why we often ask you to send us:

• A reading at RO / 0 ml/L minerals and

• A reading at 4.5 ml/L minerals

From these two points we create a theoretical chart that matches your meter to our internal reference, so we can interpret your numbers correctly.

10. What TDS readings should I send to Bluewater Support?

When we ask for TDS measurements, we usually request:

1. RO reading—mineral dosing set to 0 ml/L (RO only or lowest step).

2. Maximum dosing reading—mineral dosing set to 4.5 ml/L (or the highest step we specify).

3. Your normal working setting – TDS reading with your usual mineral dosing (for example 2.5 or 3.0 ml/L).

Please include:

• Each TDS value, and

• The corresponding mineral dosing setting (ml/L) used for that measurement.

11. What can TDS results tell you about my system?

By comparing your TDS measurements with our expected values, we can:

• Check if the dosing pump is adding minerals correctly (TDS should increase stepwise as dosing increases).

• See if the RO purifier is doing its job (TDS at 0 ml/L should be low).

• Detect possible issues such as a leaking membrane (letting too much TDS through) or a dosing problem if the TDS doesn’t follow the expected pattern.

12. Common mistakes to avoid when measuring TDS

• Measuring hot or previously heated water instead of cold water from the Bluewater faucet.

• Forgetting to flush at least 1 liter before taking the sample.

• Using a meter with a 0.5 conversion factor but not multiplying the values by 1.4 when comparing with Bluewater’s reference numbers.

• Relying on a very cheap meter and assuming it is perfectly accurate—we can work with it, but we consider it approximate only.