As if you didn’t have enough to worry about with adding sanitizer, keeping your hot tub from foaming, and making sure the heater works properly, now you have to worry about how tub scale.
It won’t make you sick, no. But if you don’t address it quickly enough, you may find yourself with a bigger problem than just some ugly buildup on the shell.
You know water contains minerals. Some water sources contain more minerals than others. Over time, these minerals will build up and leave behind hot tub scale on the shell and fixtures.
This buildup isn’t dangerous—just unsightly. The real problem lies inside your hot tub’s fixtures and plumbing. If hot tub scale gets too far out of hand, it can damage fixtures and clog the plumbing.
But hot tub scale has other causes aside from water.
Removing it once it’s there is fairly easy. But the key to caring for your spa is knowing what causes hot tub scaling in the first place so you can prevent it.
When a water source contains high levels of calcium and magnesium, it’s known as hard water. If you live in an area with hard water, that’s probably what you’re using to fill your hot tub.
When the water in your hot tub evaporates, minerals are left behind, and they’ll cling to the spa shell and fixtures. You’ll replace the lost water, and it’ll evaporate again, leaving behind more mineral deposits. After a while, you’ll have mineral buildup on the hot tub walls and fixtures.
Related to hard water, when a water source contains a high level of dissolved solids, it’s considered alkaline, especially if lime is present. These dissolved solids work the same way calcium and magnesium do in evaporated water—they stay behind and create hot tub scale.
You can follow our guide on how to lower the alkalinity in your hot tub.
Our bodies are constantly producing oils. Even when you’ve just showered, even if your skin is dry, your skin produces natural oils. And if your skin is dry, your body is also sloughing off bits of dry skin on a regular basis.
Then there’s all the hair your body loses, anywhere from 50 to 100 strands every day. We’re not going to talk about all the other substances human bodies secrete.
The point is, every time you step into your hot tub, so do all of those other contaminants. Over time, if you’re not keeping your hot tub clean, they’ll create and contribute to hot tub scale.
When you take a shower, you come out nice and clean. But what you don’t see is all the residue left behind by your soap, shampoo, shower oil, and any other products you use when you bathe.
That residue mixes with the spa water, and—you guessed it—contributes to hot tub scaling.
Sounds like it’s best just to stay out of your hot tub altogether, huh? Not at all! The first step will be to remove any existing hot tub scale. The next step will be to take measures to prevent it, and save yourself a lot of work in the future.
Get ready to roll up your sleeves. Removing hot tub scaling isn’t impossible, but depending on its cause and how long it’s been building up, it may take some elbow grease.
Sounds pretty obvious, right? And it is. If the scaling is mild, you may be able to simply apply a little hot tub scale remover and be done with it.
The only thing is, you’ll need to be very careful not to get any cleaning agents in the water. You don’t want to soak in that, do you? Didn’t think so.
Make sure the hot tub is off, and carefully clean the shell just above the water line, and any accessible fixtures. If some of the scaling does fall into the water, don’t worry. It should be caught by the filter. If that happens, clean the filter afterward to keep the scale from getting back into the hot tub and starting the cycle all over again.
Build-up of scale or calcium carbonate can potentially harm both the surface of your spa and its circulation system. The product in question effectively prevents scale by releasing potent compounds that adhere to calcium ions in your spa water, which are often the cause of such issues.
If you’re dealing with heavy buildup, and the majority of it is below the water line, your best bet will be to drain and clean your hot tub.
With the water completely out of the way, you can apply as much hot tub scale remover as you need without worrying about dripping down into the shell. It’s also an opportunity to give your hot tub a good scrubbing all over.
To make sure you get all the hot tub scale wherever it’s hiding, also use a line flush product to get any buildup out of the plumbing.
Don't let your hot tub fill with hard-to-remove gunk. Clear out the gunk and keep your hot tub water fresh. It removes gunk in your pipes caused by lotions, sunscreens, cosmetics, etc.
Once you’ve done all that work to get rid of it, you’ll want to make sure that hot tub scaling doesn’t come back.
If your filter is doing its job, it’s trapping a lot of those contaminants that cause hot tub scale. But if it goes too long between cleanings, it’ll catch less and less dirt and debris, and it’ll all just start building up in the water, and in your hot tub. Keep the filter clean to help keep your hot tub clean and free of scale.
Soak your hot tub filters in this deep-cleaning solution, rinse with water, and your filters will look brand new in 24 hours!
This is inarguably the most important part of hot tub maintenance. Aside from just keeping the water clean, it’s crucial to preventing hot tub scaling.
Because it acts as a buffer for pH, alkalinity should always be adjusted first. Alkalinity refers to the ability of your water to neutralize acids. If alkalinity is high, chances are the pH will be high as well. If the alkalinity is low, the pH level will probably also be low.
Total alkalinity (TA) should be kept somewhere between 80 and 120 parts per million. Once you get the TA level in the correct range, you’ll have a much easier time maintaining the pH level, and controlling scale buildup.
The recommended pH range for hot tub water is 7.4 to 7.6. High water temperatures in your hot tub can make the pH level climb, so keep an eye on the thermostat. A high pH level can cause calcium to build up on the surface of your hot tub. Keep the pH level within the optimal range to help prevent hot tub scale.
Tests for 7 important chemistries in seconds: Total Hardness, Total Chlorine, Total Bromine, Free Chlorine, pH, Total Alkalinity, and Cyanuric Acid.
If you live in an area with hard water, you start down the scaling path every time you add water to or refill your hot tub.
To prevent buildup, try using a hose filter to remove some of the minerals from the water while you fill your hot tub. If that doesn’t help, you can add water softeners to reduce the amount of minerals in the water.
Fill your pool or hot tub with this hose filter that'll filter your water so you can have a fresh start with water chemistry.
Easily added to your hot tub water, a scale preventer will do most of the heavy lifting for you. If you’re averse to adding yet another chemical to your spa water, though, just stick to the other prevention methods.
Quickly remove metals like iron and copper from your hot tub water.
Look, we get it. Cleaning a hot tub can be a hassle. But it’s one of the best ways to avoid hot tub scaling as well as keep mold from growing, and keep from developing a rash every time you soak.
Keep the areas above the water line clean, and do a full draining and cleaning on a quarterly basis, more often if you use the hot tub often or have a high bather load.
Our once-a-week treatment combines hot tub cleaner, conditioner, and water clarifier to give your hot tub water a soft & silky feel. Plus sparkling clean water!
Even if you live in an area with the hardest water ever, there’s really no excuse for allowing hot tub scale to build up and take over your spa. Keep it clean, keep the water balanced, and take appropriate measures at the first sign of buildup, and your hot tub will last you a good, long time.
Happy Soaking!
Matt is the founder of Swim University. He's been in the pool industry since 1993. His mission is to make pool care easy for everyone. Each year, he continues to help more people with water chemistry, cleaning, and troubleshooting.
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