Calcium Hardness In Your Hot Tub: Everything You Need To Know

Calcium isn’t only found in milk, and it isn’t as good for your hot tub as it is for your bones (at least not in high amounts).

While your water does need some calcium to keep your pH levels balanced, having high levels left unchecked can leave scaling and buildup that is difficult to remove and cause irritation to the skin and eyes of its bathers. 

>>Read: How to lower pH in your pool

On the other hand, though, low calcium hardness levels can wreak havoc on your tub and plumbing and leave your skin feeling slimy and unclean.

All your chemistry levels work together to keep each other balanced, so when one is off, chances are another is off as well.

The answer is to keep them all within the proper ranges so they can all work together to keep your water clean and clear.

Ideal Hot Tub Chemistry Levels

For most hot tubs, the appropriate levels are:

  • pH balance: 7.2-7.8
  • Alkalinity: 80-120 ppm
  • Chlorine: 1.5-3.0 ppm (or) Bromine: 3.0-5.0 ppm
  • Calcium Hardness: 80-200 ppm

So, let’s take a look at this a little more in depth to help you understand how to measure the calcium hardness level and adjust it when needed.

Why Calcium Hardness Is Important

Ever heard the terms soft or hard water?

What this refers to is the calcium hardness levels.

High levels can make the water feel “hard” and low levels can make it feel “soft.”

If you bathe or swim in hard water, you’re likely to come out feeling itchy or dry, while soft water can leave you feeling a little slimy, especially if it is extremely soft.

But what’s that all mean?

Calcium hardness is simply the measure of the calcium (or lime) that is present in the water.

It might sound like kind of a silly thing to worry about, but your hot tub water depends on every level being in balance in order to be safe and clean. 

Here are some specific things that out-of-balance calcium hardness causes:

  • Etching. While you usually won’t have much cement or plaster directly around your hot tub, this is something to be aware of. Low calcium hardness levels can cause etching (or pitting) in the plaster or cement in and around your pool or hot tub. This is because your water will start to “crave” calcium and start eating away at the materials that contain it.
  • Scaling. High calcium hardness levels can start to cause buildup or scaling on hot tub equipment. It can cause plumbing issues, clogging of filters and unsightly deposits that are hard to remove. 
  • Skin and eye irritation. High calcium hardness levels can throw off the pH balance, causing irritation and dryness to the eyes and skin.
  • Cloudy water. This usually happens with high calcium hardness levels. It starts building up and clumping together, leaving residue in you hot tub that leaves the water looking murky.
  • Corrosion. Anything metal can start to suffer from corrosion in low calcium hardness level water. So, metal plumbing fixtures, etc. 

What’s The Ideal Calcium Hardness Level For A Hot Tub?

The ideal calcium hardness range for a hot tub is 80-200 ppm.

These ranges are a good guideline because anything above or below means your water is way out of range.

And anything above 1,000 ppm is considered EXTREMELY high.

These levels will always vary slightly, and actually, each hot tub manufacturer usually list their own ranges for their specific hot tub models. 

Balancing Calcium Hardness

This level should be tested with all your others on at least a weekly basis, and most pool test kits come standard with a calcium hardness test.

The only time I would recommend checking it more often is if you’re having problems with your water.

Usually if these levels are too high or low, it will throw everything else out of balance or it’s because something else is out of balance.

In those cases, you might need to run all the chemistry tests daily until you get it corrected. 

Low Calcium Hardness

If your hot tub water is a little too soft, it’s not too terribly difficult to adjust with a calcium hardness increaser.

It’s really as simple as adding a little calcium to the water. Just don’t go crazy.

Read the instructions to find out how much you should add for your particular hot tub and start with the smallest recommended amount.

Remember that it’s easier to raise calcium than to lower it.

High Calcium Hardness

On top of all the other annoying things high calcium hardness levels can cause, it will also prevent your other chemicals from dispersing properly in the water and doing their jobs.

But this isn’t as easy to fix as low levels. 

If you’ve done everything you can to get all your other chemistry levels balance and you still can’t get the calcium hardness level to come down, you’ll most likely have to drain your water and start over.

There are chemicals you can use to reduce the levels, but I don’t like to add more chemicals unless it’s totally necessary.

That is up to you, though!

But since hot tubs are not that difficult to drain, this is what I recommend. 

However, if you continually have this issue, there’s probably a high supply of calcium in the water you are using to fill your tub.

In this situation, I recommend using a pre-filter that attaches to your hose while you’re filling the hot tub. 

It’s a good idea to use these when you fill your hot tub anyway because they are relatively inexpensive and they can help remove most chlorine sediment and other high metal and mineral compounds from your water supply.

This can save you a lot of time and money on all your hot tub chemicals.

Bottom Line

Calcium hardness is one of the most important levels to keep balanced in hot tubs because of the damaging conditions it can cause when it’s not. 

Chances are you know the water conditions where you live, so you probably already know what to expect.

Using a pre-filter no matter what your water conditions are, like I suggested earlier, will nip a lot of potential problems in the bud as well as help you save money on chemicals. 

Have you had trouble with out of balance calcium hardness levels?

Let us know what worked for you!

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