HM Digital DM-1 In-Line Dual TDS Monitor, 0-9990 ppm Range, +/- 2% Readout Accuracy,Blue & White

a must have. this tells me my TDS out of the tap and after my DI unit (0 out tyvm!) :) make sure you install correctly. there is only 1 way to install them into the line to read correctly, so follow the directions! a must have for a reef tank ro/di unit!

Quick install and upgrade at a great price

I could hardly believe how easy this instrument was to install. It must have taken me at least two minutes and it was up and running producing accurate results, I checked it with my handheld meter. The display is a little small but that's no big thing. Pun intended.😀 a great buy in my opinion.

This meter functions fairly well. If the two sensors don't have enough water around them in fitting they read low, so they need careful placement in T fittings. The meter output matches handheld conductivity and its inexpensive. My main issue is the low contrast LCD display that requires direct view and more than ambient light. The product concept is great and it's easy to switch from source water to RO.

Easy to hook up took 5 min tops. Have one probe on waste water and the other after the DI media. Takes the guess work out of when to change DI media!

I installed our first RO water purification system 18 months ago...extremely delighted..pleased with the pure water...routed 2 ..1/4 inch pure water lines ...1 to our Sam Sung fridge...in door water...& .ice crushed..or whole..the 2ed..a single lever pure water faucet on kit sink rim.Over time I wondered about the performance of the RO process...a small hand held PPM...( parts per a million ) instrament...purity tester...seemed to work nicely ..and simple readings.I noticed this In line PPM water ...TESTOR... two sensors..LCD readout...miniature sized ..at a reasonable price....clicked ..that Amazon TO CART...Prime...Thu..arrived Saturday.Installed easily....also...that saying...BATTERIES INCLUDED....installed..ready to test ones water...in coming...and Out going after the RO PROCESS. THE probes..2..all ready to insert into a T fittings.. included.and both pre wired...aprox 2,5 feet of electrical wires attached...a pair of Velcro pads on case rear..stick on and read the display ..raw water in..slide switch on display..throw switch other direction...LCD..reads purified RO water out.A small but detailed operation fold out sheet..simple details to install..About 1/2 hour..all set to test.A small on..off button..auto turn off also..HAY..,! This little read out..it works great..!For sure..5 stars...a must have to monitor your RO pure water delivery....

I have tested behind this product. I use the system for my salt water aquarium so water has to be randomly tested. Never had an issue.

I feel that this is VERY accurate. I purchased a reverse osmosis system and installed both the meter and the system at the same time. Before installing the TDS I tested a cup of water by dipping the prongs directly into the cup of water. It gave a reading of 144ppm. I hooked up the system and tested the incoming again and it tested 144ppm exactly. The outgoing started off at 30ppm but because of the Osmosis system being brand new I had to run it through a few times and over the course of that day it steadily dropped all the way down to 6ppm. Our system has been hooked up and used EVERY day now and its reading 12ppm, and holding roughly steady plus or minus 1ppm. I know a lot of you that read this and have done your homework on TDS will say that there was no reason to purchase the Reverse Osmosis system with a testing of 144ppm, but I wanted to be sure that with our well water that 99% of the toxins are being removed. To be honest most of the TDS reading in my water is the water softener, being that I have 3 charcoal filters before it reaches the TDS meter.