Can you use Rainwater in a Hot Tub? Tips for Free Water

Hot tubs require a lot of maintenance that includes filters, chemicals, water maintenance and refilling the hot tub when you lose water. To save on water usage, people often wonder if they can use rainwater to refill their hot tub. 

It’s perfectly fine to use rainwater in your hot tub. You can collect rainwater through a drainage system on your home and take it straight to the hot tub, or you can collect it in barrels and dump it in later. Either way, however, make sure that you have a filter system to collect dirt and debris from your rainwater before it enters the hot tub. 

Using rainwater in your hot tub does a good job of saving water, but it also requires extensive filtering and cleaning. People often make the mistake of assuming that rainwater is clean because it’s natural. While that’s true to a certain extent, rainwater still needs to be filtered. 

Is Rainwater Bad for Hot Tubs? 

Rainwater in itself isn’t bad for hot tubs, but it often contains dirt and dust that can be bad for it. Using rainwater is fine for your hot tub, but there are certain measures you should take before using it. Because rain is from a different source than your tap water, the alkalinity will be different. Rainwater also picks up dirt and pollution as it’s falling through the air. 

How to Use Rainwater in My Hot Tub 

If you’ve made the decision to use rainwater to keep your hot tub water levels where you want them, here are some important details you need to know. There are several ways to collect rainwater and we’ll discuss each one so that you know what to expect. 

Collecting Rain in Water Barrels 

One of the ways that people collect rain for their hot tubs is by capturing it in barrels, called rain barrels. Capturing water in barrels before transferring it to your hot tub allows you to adjust the alkalinity and control how much water you’re adding. 

Close up on Green recovery of rainwater in a garden

It’s important to purify and decontaminate rainwater that you’ve collected in barrels before adding it to your hot tub. There’s a good chance that your water will have dirt, dust, and pollution in it. This can happen as rain falls through the air or while it’s sitting inside the barrel during the collection process. 

Funnel Water Directly Into the Hot Tub 

Another method that people like to use is to filter water directly into the hot tub. Using this method, rainwater is usually taken from the roof of a nearby building or house and piped into the hot tub. Here’s how it works. 

  1. Rain lands on the roof of whatever building your hot tub is closest to. 
  2. Because your rain gutters are filthy, you want to avoid collecting water out of them. You should set up a piping system similar to your rain gutters that captures some of the rain washoff before it enters the gutters. 
  3. Run your piping system down to your hot tub, but not directly into it. 
  4. Install a filtering system for the rain to go through before it enters the hot tub. Rain collects bacteria, pollutants, and dirt as it’s falling and after it lands on your roof. You don’t want all that garbage getting into your hot tub. 
  5. After the rainwater is sufficiently filtered, it will naturally flow into the hot tub and join the rest of the water. 

Using this method isn’t as precise or efficient as using rain barrels, but it works. The advantage of using rain barrels is that you can filter the water better and add chemicals to it before adding it to the hot tub. This will make so that your hot tub doesn’t have to work as hard to integrate the new water. 

Some people also use the method of simply removing the hot tub cover during a rain storm. While this is the easiest way to add water to your hot tub, it’s also the worst way. You’ll have to add chemicals and clean your hot tub more often if rainwater isn’t filtered before it enters the hot tub. 

Does Rainwater Affect Alkalinity in a Hot Tub? 

One of the downsides of using rainwater in your hot tub is that it lowers the alkalinity. Alkalinity refers to how acidic something is and when too much rainwater enters a hot tub it alters the alkalinity. While you don’t want high alkalinity because that would be dangerous, you also don’t want it to be too low. Low alkalinity can result in corrosion of the metal components on your hot tub. 

Unbalanced alkaline will also result in greener, nastier water. It’s important that you use a pH increaser or decreaser whenever necessary. You should also test the alkalinity of your hot tub on a regular basis, especially when you use rainwater. Alkalinity adjustment is where it’s very handy to use rain barrels. You can test the alkalinity of each barrel and raise or lower it to match your hot tubs alkalinity. 

Can I Leave My Hot Tub Out in the Rain? 

Leaving your hot tub out in the rain isn’t a big deal. While there are some who prefer to have their hot tub underneath a shelter of some sort, it’s totally preferential. A little rainwater isn’t going to hurt your hot tub, you just might have to adjust the alkalinity and add chemicals more often. 

Can I Use My Hot Tub in the Rain? 

Not only is using a hot tub in the rain perfectly safe, it’s also therapeutic! There’s nothing like feeling the cool rain fall on your skin in conjunction with the heat of a hot tub. There are actually times when people purposely wait until it rains to use their hot tub. 

However, it’s important to check your hot tubs alkalinity, cleanliness, and chemical balance after using it in the rain. You should perform these checks regularly anyway, but it’s especially important after lots of rainwater enters the tub. 

Are Hot Tubs Dangerous During Thunderstorms? 

While hot tubs aren’t dangerous when it’s only raining, you shouldn’t use one during a thunderstorm. The rain and thunder aren’t dangerous, but lightnigh can be deadly if it strikes you while you’re in water. Staying out of your hot tub during a thunderstorm also applies to indoor hot tubs. 

Water is an excellent conductor of electricity and amplifies the electrocution you would experience. It’s safe to use hot tubs in nearly all kinds of weather outside of thunderstorms.  

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