Cheap TDS Meters

SuperJ

I'd like to get a TDS meter to monitor my home system.
I noticed there are bunch of pretty inexpensive ones available.
Can I trust something that costs less than $20?
Or is it basically like commodity technology (like PH testing). You don't have to pay much for a PH test you can trust.

NY_Rob

I bought one of the $20 TDS meters... It's results were in line with our published local city water results, so I took it as being accurate for boiler water testing.

Canucker

How often do they need to be calibrated? Our pH meters are calibrated before each use. I imagine a TDS would need to be but not as often

hot_rod

Do you have a ph meter? You need one for testing glycol. If not look at a dual meter like this. Most come with recalibration fluids, for the ph side. 60 bucks should buy a good enough dual meter.

SuperJ

Good idea, I'll look into dual meters. I had been using litmus paper for PH.

DavidMitten

Until 5 years ago I did a lot of industrial water quality testing as a chemical technician. Companies like Cole-Parmer might have cheaper instrumentation that will get you good results.
TDS on a meter such as those made by Myron is simply a calculation. So, you could check either conductivity and calculate the result as a percentage or check TDS.
I think that you can test TDS on a Hach DR 2000. We picked up one of those, used, for about 100 dollars. You can do all sorts of testincluding soil testing and drinking water testing and stuff with one of those. You simply must get reagents for each test and instructions.
Hach did manufacture a dedicated TDS meter- a spectrophotometer type that was quite small as well. You might be able to get one of those used from a university or e-bay or something.

For calibrating, you purchase a calibration standard. You rinse the meter three times, then test on the fourth go. Lots of repetition is involved in water testing. It was fun at the time(sometimes).

Finally, as an aside, I have not tested for glycol amount in a system, but a simple refractometer should be all you need to test for that.

DavidMitten

The other thing is litmus paper can be fine for testing pH. The key is getting paper for your specific testing range. For instance, some pH paper has a range from 7-12, but if you know that you are testing for pH from let's say 8.2-8.5, then you can buy a pack with a range 8.0-9.0. They work quite well.