Frequently Asked Questions

Frequently Asked Questions

pH Meter FAQ

How do I calibrate my Waterproof pH Meter?

Where do I get my Free pH Food Chart?

TDS Meters FAQ

What should the TDS level of my water be?

TDS, EC and Colloidal Silver

Why do I experience different TDS readings in the same water with the same meter?

How can I get the best possible TDS readings?

Can I use the cap as a receptacle for testing?

Are TDS meters really conductivity meters?

Is pinpoint accuracy always necessary when testing for TDS or conductivity?

How do I use a TDS meter to test for salt in salt generator pools?

Can a TDS meter be used for testing water softeners?

What is the difference between a parameter and a scale?

Is “EC” a parameter or a scale?

What’s that little µ symbol on my EC meter?

How do I convert from EC (µS) to TDS (ppm)?

How do I convert from TDS (ppm) to EC (µS)?

Do you need the minerals in your drinking water?

Can I test hardness with my TDS Meter?

Can I calibrate my TDS Meter, myself?

What should the TDS level of my water be?There is no specific level nor ‘good or bad’ answer to this question. Generally speaking, for drinking water, a lower level of TDS (purer water) is preferred. The U.S. EPA, all U.S. states, the World Health Organization (WHO) and most nations put maximum limitations on TDS allowed in drinking water. These limitations are typically 500 or 1000 ppm, but they do vary. There is no known minimum for drinking water.Besides drinking water, a TDS level is specific for each application and particular usage. Though humans generally prefer purer water for their health, fish and plants, for example, require water with widely varying TDS levels, most of which are higher than healthy human drinking water. If you are using a meter to test the water pertaining to a particular device, object or operation, contact the manufacturer of that object. For example, if you are using the meter to test the efficacy of a water filtration system, contact the manufacturer of that system for preferred TDS levels. If you are testing the water for a pool, plants, fish, etc. contact a specialist for your specific application, or the manufacturer of additives or nutrients.TDS ppm ChartWhy do I experience different readings in the same water with the same meter?Reasons for varied readings include:

Ions: The nature of charged positive ions (which is what the TDS meters are measuring) is that they are always moving. Therefore, there may always be variances in the conductivity, and thus a different reading.

Temperature: Even with ATC (Automatic Temperature Control), temperature changes by a tenth of a degree may increase or decrease the conductivity. Additionally, the temperature coefficient (what the reading is multiplied by to adjust for temperature differences) changes slightly depending upon the range of ppm. Our meters and virtually every meter under $500 has a single temperature coefficient, regardless of the range.

Air bubbles: Even a tiny air bubble that has adhered to one of the probes could potentially affect the conductivity, and thus the reading.

Lingering electrical charges: Electrical charges off fingers, static eletricity off clothes, etc. on the meter and lingering electrical charges in the water will affect the conductivity of the water.

Beaker/cup material: Plastic cups retain lingering electrical charges more than glass. If the meter touches the side of the glass or plastic, it could pick up a slight charge. If the plastic is retaining a charge, it could also affect the water.

Volume changes: The amount of water in the sample may affect the conductivity. Different volumes of the same water may have different levels of conductivity. Displacement may affect the conductivity as well.

Probe positioning: The depth and position of the probe in the water sample may also affect the conductivity. For example, if a meter is dipped into the water, removed and then dipped into the water again, but in a different spot, the reading may change.

How can I get the best possible readings?

Shake: Always make sure to shake excess water off the meter before dipping it into a water sample, even if it’s the same water.

Stir/tap: After dipping the meter in the water, always lightly tap it against the side and stir the meter to remove any lingering air bubbles or electrical charges.

Positioning: When taking the reading, always make sure to hold the meter straight up without it touching the sides or bottom of the glass/beaker/cup. The probes should be suspended as close to the center of the water sample as possible.

Time: The longer the meter is in the water, the more accurate the reading will be. Wait until readings stabalise, usually about 20 seconds.

Temperature: 25 degrees Celsius is the ideal temperature for conductivity readings, even if the meter has ATC.

Rinse: If switching between very low and very high ppm water, always rinse the probes with distilled water to avoid any build-up.

Can I use the cap as a receptacle for testing?

No. The cap is for storage and protection only. For best results, use a larger beaker, cup, glass, etc., so there is a larger volume of water that will be tested. Additionally, to ensure a long lifespan of your product, the TDS/EC sensors should be stored dry.

Are TDS meters really conductivity meters?

Yes. While EC and TDS are often used synonymously, there are some important differences to note. EC, when applied to water, refers to the electrical charge of a given water sample. TDS refers to the total amount of substances in the water other than the pure H2O. The only true way of measuring TDS is to evaporate the water and weigh what’s left. Since this is near impossible to do for the average person, is it possible to estimate the TDS level by measuring the EC of the water. Every digital TDS meter in the world is actually an EC meter.

All elements have some electrical charge. Therefore, it is possible to closely estimate the quantity of TDS by determining the EC of the water. However, since different elements have different charges, it is necessary to convert the EC to TDS using a scale that mimics the charge of that water type. The following are the most common water samples:

KCl: Potassium Chloride is the international standard to calibrate instruments that measure conductivity. The KCl conversion factor is 0.5-0.57.

442TM: Developed by the Myron L Company, 442TM simulates the properties of natural water (rivers, lakes, wells, drinking water, etc.) with a combination of 40% Sodium Bicarbonate, 40% Sodium Sulfate and 20% Chloride. The TDS-EC Meter is factory calibrated with a 442 solution. The 442 conversion factor is 0.65 to 0.85.

NaCl: Sodium Chloride is used in water where the predominate ions are NaCl, or whose properties are similar to NaCl, such as seawater and brackish water. The NaCl conversion factor is 0.47 to 0.5.

Is pinpoint accuracy always necessary when testing for TDS or conductivity?

Usually not. TDS is primarily about range. For the majority of industries that require TDS testing, such as drinking water, aquaculture, hydroponics, etc. it is more important for your TDS levels to be within a certain range. There are a few industries that do require a precise ppm level, but that level is almost always zero. With the exception of colloidal silver, there is never a time in which someone needs an absolute precise level of TDS in their water.

How do I use a TDS meter to test for salt in salt generator pools?

Any TDS meter can be used to test for salt (up to the maximum range of the meter). Salt is a part of Total Dissolved Solids and therefore will be part or all of the reading. If you are first filtering the water, and then adding salt, simply use the meter as you would under any circumstances. If there is only salt in the water, and the reading is 2500 ppm, then that is 2500 ppm (mg/L) of salt. If you are starting with tap water and filling a pool, for example, prior to adding salt, then first test the level of your tap water. Therefore, if your tap water is 200 ppm, and your pool needs to be 3500 ppm of salt, then add 3300 ppm of salt. (A small portion of the tap water TDS may be salt.)

Can a TDS meter be used for testing water softeners?

No. Water softeners do not remove TDS. Instead, water softeners work through a process of ion exchange. As water flow through the water softener, it will pass through a resin, bed of small plastic beads or chemical matrix (called Zeolite) that will exchange the calcium and magnesium ions with sodium ions (salt). Therefore, the TDS level will remain virtually constant (there may be minor differences).

What is the difference between a parameter and a scale?

A parameter is the characteristic being measured. A scale is a particular range applied to the measurement of that parameter. For example, temperature is a parameter. Fahrenheit or Celsius is a scale.

Is “EC” a parameter or a scale?

“EC” is a parameter. It stands for Electrical Conductivity. There are a number of scales used in EC, most commonly micro-Siemens (µS) or milli-Siemens (mS). For example, if a particular application calls for water with “2.0 EC,” this is an incorrect determination. Most likely, the application is calling for an EC level of 2.0 mS. 2.0 mS = 2000 µS.

What’s that little µ symbol on my EC meter?

The symbol ‘µ’ is not a lowercase U, but the Greek letter Mu. It is the abbreviation for micro, and when used with an S (µS) it stands for mirco-Siemens, which is a scale used for measuring EC.

How do I convert from EC (µS) to TDS (ppm)?

The best thing to do is use a TDS meter, which will automatically do the conversion. EC meters do not use conversion factors because there is no conversion. To convert to TDS, if you do not wish to use a TDS meter, you will need to determine which conversion factor you want to use (NaCl, 442 or KCl) and do the math.

How do I convert from TDS (ppm) to EC (µS)?

The best thing to do is use an EC meter. If you know which conversion factor your meter uses, you can do the math. Most Digital Aid meters use the NaCl conversion factor, which is an average of 0.5. Therefore, if you are using a TDS meter with the NaCl conversion factor, multiply the reading by two, and this will get you a close approximation of the EC level.

Do you need the minerals in your drinking water?

Inorganic Minerals

It is believed that mineral waters help furnish elements for body metabolism. However, there is scientific proof to suggest that most of these minerals are in an inorganic (dead) form. While they may enter the circulation, they cannot be used in the physiological process of building the human cell.

With this in mind, we can see that mineral water may give “dead” or “inorganic” minerals to the body which cannot be properly assimilated.

These inorganic minerals only interfere with the delicate and complex biology of the body.

The body’s need for minerals is largely met through foods, NOT DRINKING WATER.” -The American Medical Journal

Fact: The organic minerals in tap water represent only 1% of the total mineral content of the water.

One glass of orange juice contains more beneficial minerals than thirty gallons of untreated tap water.

Organic, or Bioavailable Minerals

Only after they have passed through the roots of plants do these inorganic minerals become organic (through photosynthesis) and capable of being assimilated into our tissues as ORGANIC Minerals.

Pure water removes the inorganic mineral deposits in your body. Organic minerals are fully absorbed and remain in your tissues.

According to many nutritionists minerals are much easier to assimilate when they come from foods. Can you imagine going out to your garden for a cup of dirt to eat rather than a nice carrot; or drinking a whole bathtub of water for LESS calcium than that in an 8 ounce glass of milk?

Can I test hardness with my TDS Meter?

A TDS Meter tests the number of particles in the water, not the type of particle nor the chemical composition of the particles.

A TDS Meter is NOT the same as a hardness test strip – Water hardness is caused almost entirely by calcium and magnesium ions, while by its very nature a water softener is designed to replace hardness with sodium. It is called a one for one ionic exchange.

For example if you have 200 PPM of hardness it will be converted to at least 200 PPM of sodium. Our tests show you can expect an additional 20% in residual salt and sodium after that exchange in most cases. In other words 200 PPM of hardness will usually be replaced with 240 PPM of sodium.

Thus the TDS Meter will show an increase in the parts per million due to the increase in sodium which is ignored by the Test Strips. That would explain why PPM is higher on the softened water than the original hard water.

Can I calibrate my TDS Meter, myself?

Your TDS-EC Meter is factory calibrated and should never need re-calibration, however if you are determined to calibrate it on yourself there is a little work involved. If you suspect the meter is not accurate, after checking all the steps of “How can I get the best possible readings?” above, you can contact customer service to get your TDS-EC meter replaced, or attempt the following:

TDS_METER_with_hole_cut_big TDS_Meter_with_calibration_hole_big TDS_Calibration
  1. A small hole needs to be cut through the plastic face just to the left of the Shift button, either a small cross or plus with an Xacto knife or hand drill a 1/16″ hole.
    Note: The Version 2.0 is manufactured with the calibration hole already cut in the front face.
  2. Switch the TDS-EC Meter on and place it in the calibration solution – use NaCl 342ppm.
  3. Using a small jewelers screwdriver adjust the screw until the correct reading (342ppm) is obtained. (The cover was taken off this meter for clarity.)