"Is reverse osmosis worth it at my address?" The answer is not in a catalog but in three numbers: what is in your water, how much drinking water you use, and the full cost of the machine over several years. This section gathers the tools and methods to get those numbers before buying rather than after.
Reading your water report
Every community water system in the country has to publish an annual Consumer Confidence Report, and I republish them city by city in the water quality register. The lines that justify reverse osmosis — or do not — are: PFOA and PFOS (federal limit 4 parts per trillion each, and the most common reason to buy RO today), arsenic (10 ppb, a matter of local geology across much of the West and Midwest), nitrate (10 ppm, mostly farm country), and lead, where the report tells you about the distribution system and your own plumbing tells you the rest.
Hardness appears on some reports too, but an important reminder: scale is not a health problem, and reverse osmosis is not the right answer if it is your only concern. For that, look at a softener instead.
Testing station
What's in your tap water?
Enter your ZIP code and I'll pull up what your own water utility reported, straight from its annual Consumer Confidence Report.
Working out the full cost
Reverse osmosis is almost always compared against bottled water, so let us set the calculation out. A family buying two cases of bottled water a week spends $300 to $600 a year, before counting the carrying and the plastic. Against that: an RO system at $200 to $550 to buy plus $50 to $80 of consumables a year. It pays back in under a year in most households, and RO water then costs a few cents a gallon.
Add the wastewater to be complete: at 2 to 4 gallons to drain per gallon produced and about a gallon and a half of drinking water a day, the extra on the water bill stays in the range of a few dollars a year. That is not where the calculation is decided.
The $15 meter that tells the truth
A TDS meter measures total dissolved solids in seconds. Before buying, it puts a number on your starting point; after installation, it verifies that the membrane is holding back more than 90% of dissolved solids, and it tells you when it is tiring. It is the one instrument I consider essential alongside an RO system.
The model I recommend is as dumb as possible, and deliberately so: an HM Digital TDS-EZ — one button, one screen, one battery. The "3-in-1" versions that add conductivity and temperature cost the same and pile up numbers you will do nothing with.
HM Digital TDS-EZ meter
Strong points
- The simplest way to check an RO system is still doing its job
- Reads in seconds, factory calibrated, 0–9990 ppm
- Cheap enough to keep under the sink
Weak points
- TDS is not a health measure: it says how much is dissolved, not what
- No automatic temperature compensation, so cold and warm samples do not read alike
- Says nothing about lead, PFAS or bacteria
Where to buy
- Amazon$15 See price
A word on what TDS is not: it is not hardness, and it is not a health measure. It adds up everything dissolved — calcium included, but not only. A high TDS does not mean dangerous water, and a low TDS does not mean safe water: lead at 20 ppb and PFOA at 8 ppt will not move the needle at all. For those, only a certified lab test on your own tap will do.
Certified lab water test kit
Strong points
- A certified lab, not a strip: the only way to get a real lead or PFAS number at YOUR tap
- 116 analytes, including lead, copper, hardness and alkalinity
- Covers what a Consumer Confidence Report structurally cannot — your own plumbing
- Written report with the federal limits alongside your results
Weak points
- Ten to twenty times the price of strips
- Two to three weeks for results
- One snapshot in time, not a monitoring program
Where to buy
- Amazon$179 See price
