Digital TDS Meter, TDS-3 beige pen-style meter with LCD display and three pink buttons, front view
Digital TDS Meter, TDS-3 beige pen-style meter with LCD display and pink buttons, angled front view
Digital TDS Meter, TDS-3 meter lying at an angle with cap removed showing the probe tips
Digital TDS Meter, close-up of LCD display and HOLD, TEMP and ON/OFF buttons on a beige meter
Digital TDS Meter, TDS-3 beige pen-style meter with LCD display and three pink buttons, front view
Digital TDS Meter, TDS-3 beige pen-style meter with LCD display and pink buttons, angled front view
Digital TDS Meter, TDS-3 meter lying at an angle with cap removed showing the probe tips
Digital TDS Meter, close-up of LCD display and HOLD, TEMP and ON/OFF buttons on a beige meter

Digital TDS Meter

$27.45

Check your water's dissolved solids in seconds, and see when your RO membrane is due.

Read more
Model, TDS-3 (TDS + Temp)
Digital TDS Meter, white TDS & EC meter lying at an angle with cap removed showing the probe tips

How do I use it?

No installation. Take the cap off, dip and read.

  1. Take off the protective cap.
  2. Press ON/OFF to turn the meter on.
  3. Pour room-temperature water into a clean cup and dip the tip in no deeper than the immersion line, about 3 cm. The meter is not waterproof, so keep the display and buttons dry.
  4. Stir gently and wait for the reading to settle. On the TDS & EC model it locks on the display within 5 seconds.
  5. Press HOLD to freeze the reading, then lift the meter out to read it.
  6. TDS-3: press TEMP to see the water temperature. TDS & EC: press SHIFT to switch between TDS, EC and temperature.
  7. Wipe the tip dry with a soft cloth, put the cap back on and turn the meter off.
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Shipping

Free shipping on orders over $150

Residential addresses in the lower 48 US states. Excludes business addresses, commercial and industrial systems (which ship by freight), and filter media sold by the bag or cubic foot.

Order by 3:00 PM Eastern on a business day and most filters, cartridges and smaller items leave our facility that same day. Standard residential systems ship within 1 to 2 business days, and whole house, custom and specialty systems typically within 3. So far in 2026, 95% of our orders have shipped within one business day and 99% within five (based on an internal review of our order records).

Once shipped, standard delivery typically arrives in 3 days to the Southeast, Northeast and Southwest, and in 4 days to the Midwest and the West. Need it sooner? UPS 2nd Day Air and Next Day Air are available at checkout for eligible products. Systems that ship by freight can take longer and may need a delivery appointment.

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Lifetime support

Our team answers questions about products, orders, installation, troubleshooting and replacement parts.

Phone: 770-951-5600 or (800) 934-0051

Email: help@crystolquest.shop. We reply within 24 to 36 hours.

Live chat during business hours

Hours: Monday to Friday, 9:00 AM to 5:00 PM Eastern. We observe U.S. federal holidays.

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Digital TDS Meter

One number for your water. In seconds.

Dip it in a glass and read it. A TDS meter is the quickest way to see your filter or RO system at work.

Hand dipping the tip of a TDS-3 meter into a glass of drinking water
TDS and EC meter reading 412 µS/cm in a glass of water, aquarium and hydroponic greens behind

How a TDS meter reads water

Two metal probes pass a tiny current through the water. Dissolved minerals and salts carry that current, and the meter turns it into parts per million.

  • Conductivity

    The more that is dissolved, the more easily water carries current.

  • Parts per million

    The display shows an estimate of total dissolved solids in ppm.

  • Temperature

    Both models also show the water temperature.

Pick your meter

Same quick reading, two ways to use it.

  1. TDS-3

    TDS and temperature on three simple buttons. Made for checking tap, filtered and RO water at home.

  2. TDS & EC

    Adds conductivity in µS/cm, the unit growers and aquarium keepers use. Reads up to 9,999 ppm, ±5%, with automatic temperature compensation.

TDS-3 and TDS and EC meters side by side at a kitchen faucet, one testing a glass of water

Is your RO still working? Find out in a minute

Two readings and a comparison. Repeat every month or two and you will see a tired membrane coming.

  1. Tap

    Read a cup of cold tap water.

  2. RO faucet

    Read a cup from your RO faucet. It should be far lower.

  3. Track it

    When the RO number starts to climb, check your pre-filters and membrane.

TDS and EC meter reading 3 ppm in a glass of filtered water beside a reverse osmosis faucet
TDS-3 meter standing beside a glass of water on a kitchen counter

A starting point, not a safety test.

TDS counts everything dissolved, healthy minerals included. It cannot see lead, PFAS, bacteria or nitrate. For those, a certified lab test is the answer.

Why Crystal Quest

Buy your meter from people who read TDS every day, and help with what your numbers mean comes with it.

  • Over 30 years of manufacturing

    We have designed and built water filtration systems since 1994.

  • Water filtration experts

    We test water every day, so we can tell you what your reading means and what to do about it.

  • Commercial quality

    The same ISO 9001 quality system behind our commercial and industrial systems.

Questions about fit or returns? A filtration specialist answers by phone, email or chat. Read the refund policy

Is my reverse osmosis system still working? Is my filter doing anything? What is actually in my tap water? A TDS meter gives you a first answer in about ten seconds. Dip it in a glass and it shows total dissolved solids (TDS): the minerals, salts and metals dissolved in your water, in parts per million (ppm).

We use TDS meters constantly to check that an RO membrane is still doing its job. This is the same quick check, in your pocket.

At a glance

  • Reads TDS in ppm in seconds, with no strips or reagents
  • Shows water temperature on both models
  • HOLD button freezes the reading so you can lift the meter out and read it
  • Protective cap keeps the probes clean between tests
  • Two models: the TDS-3, or the TDS & EC that adds electrical conductivity in µS/cm

Which model is right for you?

  • TDS-3 (TDS + Temp): the simple one. Three buttons (HOLD, TEMP, ON/OFF) for TDS and water temperature. Right for checking tap, filtered and RO water at home.
  • TDS & EC (TDS, EC + Temp): adds an EC reading in microsiemens per centimeter (µS/cm) and switches between readings with the SHIFT button. Reads TDS from 0 to 9,999 ppm and EC from 0 to 9,999 µS/cm, accurate to ±5%, with automatic temperature compensation, a titanium alloy electrode and auto shut-off after 5 minutes. A good pick for hydroponics and aquariums, where EC is the usual unit.

How to check your RO system

  1. Run cold water from your kitchen tap for a few seconds and read a cupful.
  2. Read a cupful from your RO faucet.
  3. Compare. Reverse osmosis removes most dissolved solids, so the RO reading should be far lower than the tap reading.
  4. Write the numbers down and repeat every month or two. When the RO reading starts to climb, it is time to look at your membrane and pre-filters.

What a TDS reading cannot tell you

A TDS meter measures how easily water carries a small electrical current, then converts that to an estimate in ppm. It counts everything dissolved together, healthy minerals like calcium and magnesium included, and it does not say what any of it is. A low number is not a safety verdict: a TDS meter cannot detect lead, PFAS, bacteria, nitrate or pesticides. For those, a certified water test is the answer. Learn more in our guide, How to Use a TDS Meter (and What It Can't Tell You).

Questions? We are here

Not sure what your reading means for your water or your system? Our water specialists have helped customers since 1994. Reach us by phone, email or chat.

Goes well with

  • Quick Screen (iron, alkalinity, hardness, pH & TDS)

    $105.00

    Water test kit