What does a TDS reading mean?
TDS means total dissolved solids: the total amount of material dissolved in water. A reading summarizes dissolved material. It does not tell you exactly what is in the water or whether it is safe to drink.
What is included?
Dissolved minerals and salts contribute to TDS. Calcium and magnesium can contribute to both TDS and hardness, but the two measurements describe different things.
What a meter cannot tell you
- It cannot identify individual contaminants.
- It cannot replace a laboratory test for a specific concern.
- It cannot prove that lower-TDS water is safer or healthier.
- It cannot replace a hardness test when choosing a softener.
Why compare readings around an RO system?
Comparing feed water and RO water can help describe the system's effect on dissolved solids. Use consistent sampling conditions and the equipment instructions. A difference in readings is not proof of any specific contaminant reduction or health benefit.
What happens at Sippa's free visit?
We take a TDS reading, explain its limits and look under your sink. We check space, plumbing, the electrical outlet and the faucet location. There is no payment to book and no obligation to buy. See what the free water test includes.
If you have a specific water concern
Start with your water supplier's current water-quality report. Ask your supplier or a suitable laboratory what testing matches your concern. Do not choose treatment from a TDS number alone.
Drinking water or whole-home hardness?
Those are different projects. Our RO versus water softener guide explains the distinction. Sippa's under-sink RO package serves one drinking-water faucet.
Sources
USGS: Dissolved solids; EPA: Point-of-use reverse osmosis. Reviewed November 3, 2026.