Water Hardness Scale Chart: Do You Have Hard Water?

Nobody wants to have hard water in the house. The damage to internal piping, appliances, limescale build-up, and skin irritation are just a few problems that hard water causes.

Example of white stains hard water causes. Limescale build-up in internal piping is extremely problematic.

According to the water hardness scale, more than 85% of US households have hard water in their piping. How to know if you have hard water? Simple:

The water hardness scale is a benchmark on how hard our water is.

Here is a quick chart that gives you a spectrum of water hardness in parts per million (ppm):

water hardness spectrum and scale

Scale Of Water Hardness (From Soft To Very Hard Water)

Internationally recognized water hardness scale recognizes 4 water hardness classes – from soft, moderately hard, hard, to very hard. In the US, the unit of water hardness is usually parts per million (ppm) or grains per gallon (GPG).

Here is the full water hardness scale, according to the USGS:

Classification Hardness (PPM) Hardness (GPG) Hardness (mmol/L)
Soft 0–60 0–3.50 0–o.60
Moderately hard 61–120 3.56-7.01 o.61–1.20
Hard  121–180 7.06-10.51 1.21–1.80
Very hard  ≥ 181 ≥ 10.57 ≥ 1.81

mmol/L is a metric unit, usually in use outside of the US.

How to tell if you have hard water?

First, you have to measure the water hardness with a water hardness test. You can get it online for less than $20.

If you measure that your water hardness is below 60 ppm or 3.50 GPG, you don’t have to worry about hard water. By classification, you have soft water.

The reality is worse:

More than 90% of people find that their water is either moderately hard, hard, or very hard. Essentially, getting a 100+ ppm water hardness is not unusual; it’s actually very common.

scale of how hard water is in german degrees, parts per million, grains per gallon and mmol per L

What To Do If You Find Out You Have Hard Water?

The easiest thing is to just ignore the problem. That’s not recommended.

The immediate effects of using hard water might be apparent on your skin or on your dishes, faucets. Hard water with a high concentration of calcium and magnesium ions causes white stains pretty much everywhere.

The more concerning are the long term effects. Hard water will eventually lead to limescale build-up in your piping, washing machine, and so on, thereby limiting the lifespan of essential plumbing.

Here’s the deal:

You might not like it but fighting hard water is a smart long-term decision. Pretty much the only way that is very effective at softening water and eliminating all the problems that come with it is installing a water softener. You can find a list of the best water softeners here.

These devices are designed to reduce the water hardness from 200, 300, or even 400 ppm to below 60 ppm. This process is simply called water softening.

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