3.75 1 5 0

A TDS meter is an inexpensive and convenient digital tool to instantly check your overall water quality.

Where to buy

Seller Price Seller Rating
Show more


1 agrees

Easy to use

1 agrees

Works well

1 agrees
  • Only 3 words are allowed.

Not waterproof

1 agrees
  • Only 3 words are allowed.


A TDS meter (aka ppm pen, nutrient tester, tds stick) is an inexpensive and convenient digital tool to instantly check your overall water quality. TDS = Total Dissolved Solids, which is any salt, metal or mineral in the water. With the push of a button, the TDS-4 can tell you your overall water purity level, which will be displayed on the screen in ppm (parts per million). The lower the TDS level, the purer the water, with 0 ppm being pure H2O.

The TDS-4 is ideal for checking your tap water quality, or knowing when to change a filter. (The meter does not test for biological contaminants.) The TDS-4 is a ideal tool for drinking water, water filtration and purification, hydroponics (test your nutrients), colloidal silver, aquariums, RO/DI systems, pools and spas, and more.

Edit Delete


  • This TDS tester is ideal for all water purification applications, wastewater regulation, aquaculture, hydroponics, and colloidal silver
  • ATC (Automatic Temperature Compensation)
  • The Sleek design of the TDS-4 is perfect for personal or commercial use
  • Advanced microprocessor technology
  • Hold Function: Freeze the measurement to view it out of the water.
  • Auto-off function: the meter shuts off automatically after 10 minutes of non-use to conserve batteries
Add New

Frequently Asked Questions

  • My water tested at 244ppm before I got my water softener. Tests at 238ppm now. Softener is working, but why so little change?

    Because your water softener is simply replacing calcium ions with sodium ions, so it's normal for the reading to be about the same. Water softeners don't filter, they substitute a "softer" ion for calcium.

  • Will this meter test for hard water ?

    Sort of. The meter measures total dissolved solids, whether it is calcium or sodium or potassium it does not distinguish. Hard water is hard because the calcium is dissolved in the water, therefore if you take a reading with a hard water sample, you'll get back a reading with a high number as compared to a sample from a properly working reverse osmosis system or a sample of distilled water. Likewise if you take a reading from a soft water sample you will also get a reading with a high number as the calcium has been replaced with sodium (or potassium) in softened water. The meter is primarily to confirm that your reverse osmosis system is properly working and when the membrane filter needs to be replaced.

  • Add New FAQ

About Us