I saw something on Facebook about Carmel’s water being dangerous to drink. Is that true?

Recently, a few people on social media were discussing Carmel’s water quality because a local resident used a home testing kit to measure the Total Dissolved Solids (TDS) in his water and noticed a level above the 500 suggested by the EPA. The reason that this is not significant is that the TDS level is a “secondary standard” not required of utilities by the EPA because there is a caveat with it, a recognition that a region’s soil makeup impacts TDS levels.

This topic deserves more explanation than social media posts usually include, however, the simple answer to the question of Carmel’s water quality is this:
Carmel’s water passes all EPA and state standards and is safe to drink. 
For access to the most recent City of Carmel Water Quality Report, click here. You will see that the report shows Carmel Water had a perfect score showing absolutely no violations.

For a more lengthy explanation of TDS levels in Carmel’s water see below:
The soil and underground limestone formation in Carmel and much of central Indiana is very rich in natural mineral content, which produces a type of “hard” water that is safe, but high in calcium, magnesium, sulfates and other naturally occurring minerals.  The EPA does not consider such naturally occurring mineral content as harmful.

One thing that Carmel does, which most other cities do not, is take the raw hard water and treat it at our state-of-the-art facilities to make it softer before it reaches our customers.

Raw, untreated hard water can cause scale build-up, which can be damaging to pipes, leave spots on dishes, stain plumbing fixtures and clog shower heads. This is why decades ago, the City of Carmel made the decision to soften the water supply using the ion exchange process, which exchanges the calcium ions with sodium ions. This process does not produce soft water (as you might have with a home water softener), but it does produce water that has been made softer. One of the results of using salt to soften our water is that TDS levels are increased.

Because the EPA considers TDS levels a secondary standard, Carmel is NOT required to test these levels. However, in light of the recent discussion, we took the time to test these levels at various locations. We sampled both “raw” water (water that flows into our treatment plants) and “final” (water that has been treated and made softer).

Below are the TDS numbers for the sampling that took place October 15, 2019. Test data and test results are in milligrams per liter (mg/l)

Treatment Plant 1 – Raw 414, Final 458
  • Treatment Plant 3 – Raw 578, Final 570
  • Treatment Plant 4 – Raw 514. Final 566
  • Treatment Plant 5 – Raw 652, Final 666
Flowing Well – 512 (untreated)

One thing that Carmel does, which most other cities do not, is take the raw hard water and treat it at our state-of-the-art facilities to make it softer before it reaches our customers.

While the numbers vary from location to location, the average raw water TDS level was 540 as it flowed into our plants and 565 once it was treated. This is not significant as the EPA does not require levels lower than 500 because it recognizes that in many parts of the country, the water supply is high in mineral content. Central Indiana is among those places with high mineral content in its raw water. Some utilities in the U.S. and Canada have TDS readings as high as 1500.

We included the flowing well in our test to show that TDS levels exist in natural water that springs up unfiltered. They are not harmful and many people use the flowing well because they like the high mineral content, some even referring to it as “mineral water.”

One more test was performed on homes that use water softeners in order to have “soft water.” Two of the homes were in Carmel and one in Noblesville (which gets its water from a different utility. The results in Carmel were 688 and 700 TDS (after softening) and the Noblesville home (where the City does not soften municipal water like Carmel) the number was also 700 TDS.

What this illustrates is that by replacing the calcium or hardness ions with sodium ions to soften the water at home, TDS levels increase.

Obviously, the taste of the water is something subjective and is often based on the water we grew up drinking. But there is no question that Carmel’s water is high quality and safe to drink.

Authored by Laura Campbell, Ron Carter, Sue Finkam, Anthony Green, Bruce Kimball, Kevin Rider and Jeff Worrell