Most people install hot tubs outdoors due to their weight, size, and humidity-creating steam that quickly disappears into the atmosphere when out in the open.
The question is, can you put a hot tub indoors?
The short answer is yes, you can put a hot tub indoors. However, you need to make sure you have a sturdy floor, proper drainage, and ventilation—and of course permission from any HOA or landlord if you're not the homeowner.
But what are the benefits of doing this? Are there drawbacks? And how do you maintain an indoor tub? There are several factors you need to consider here. The information below should help you out.
How to put a hot tub indoors safely
Is the room you're thinking of suitable? Here's what you need to check:
First things first, you need to make sure the floor is a flat, level surface that can support the weight of a hot tub.
A filled spa can weigh 5,000 lbs (or even more), so it is always safest to place the tub on a concrete slab. Garage floors are perfect.
Building codes in most areas require upper floors to be built to support a minimum of 40-50 lbs per square foot, increasing to 100 lbs per square foot for balconies, so always contact a structural engineer if you're considering putting a spa on an upper floor.
As well as the weight-bearing capacity, you must also ensure the location you pick can withstand splashes or water dripping off your body as get out.
Wooden and carpeted floors can rot or grow mold and mildew, while hard surfaces with tiles, concrete, or laminate can present a slipping hazard. Your best bet is a matte, non-slip tile.
It can be expensive to change the flooring, but you can always place a bath mat by the tub in a pinch, and keep towels handy so people can dry themselves before walking back through the house.
Access to water and power
Of course, you must have access to water and electricity to fill and run the hot tub, which might require some professional installation work—especially for the source of power (assuming you want a 240V circuit instead of just plug-n-play).
Hot tubs need draining every 3-6 months. This process involves attaching a hose to the drain plug so that you can direct the water somewhere it can drain.
So, you need to set up the tub at a convenient location where you can run the hose to an appropriate drain. You don't want to cause flooding anywhere, but especially not indoors.
You may also want to consider installing floor drains around the hot tub to help with any splashing or overflow.
It may seem odd that you would have to heat a hot tub room, especially when hot tubs are often used outdoors! However, remember that hot tubs release steam through evaporation—and the bigger the difference between the air temperature and water temperature, the more evaporation you will get.
To minimize this effect and provide a more comfortable soaking experience, it's recommended to heat the air in a dedicated hot tub room to at least 26°C/79°F. This will limit the amount of evaporation and reduce the humidity in the room, creating a more comfortable and enjoyable environment for hot tub use.
The ideal hot tub room needs adequate ventilation. Firstly, it should have a window to provide natural light and ventilation. But you will also want to install a humidity-sensing exhaust fan in order to regulate the humidity levels in the room. This will prevent mold and mildew growth, as well as maintain air quality.
In some cases, you may need to install a mechanical air extraction system to effectively manage the humidity levels in the room.
It's important to note that local building codes may have specific requirements too, so consult with your local authorities before starting any renovations to ensure that your hot tub room meets all necessary regulations.
What are the best ventilation fans for a hot tub room?
You can think of a hot tub room similar to a large bathroom, just with a much larger-than-average bathtub in it! The ventilation requirements are similar, meaning you can get away with a humidistat extractor fan in most cases. That means it will detect the humidity level, and come on automatically whenever it gets too high.
Panasonic is generally considered the go-to brand here amongst pros, and this FV-1115VQ1 WhisperCeiling fan is an excellent choice:
It's a high-end fan, and is more powerful than average so should work even for larger hot tub rooms.
However, there are a few things to consider when choosing a ventilation fan:
- Pick the right size: A fan's strength (how much air it can move) is measured in cubic feet per minute (CFM). Your fan should have a CFM rating high enough to circulate all the air in your hot tub room eight times per hour.
- Check the mount style: You can get ceiling-mounted, wall-mounted, or dual-mount models. Ceiling-mounted fans are the most common, but go with what works best for your room layout and home's duct system.
- Light or no light: Some fans come with a built-in light, so you can replace your old light fixture with a fan that includes one. This way, you can use the existing wiring and get both a fan and light in one convenient package. You may or may not want this in your hot tub room though.
To determine the right fan size, first measure your room's length, width, and height. Now, you can figure out the minimum CFM rating your fan should have. Multiply your room's length by width by height by 0.13 and you'll get the minimum CFM rating you need.
For more information, Home Depot has a detailed guide to understanding more about exhaust fans. It's written with bathrooms in mind, but the basic principles are the same.
Benefits of putting a hot tub indoors
If you have enough space indoors with sturdy flooring to hold the weight of a hot tub, water, and occupants, it could be a great idea to put your hot tub indoors for the following reasons:
Reduced maintenance issues
With an outdoor hot tub, you always have to filter out bugs, pollen, leaves, and even pebbles that fall into the water.
However, the case is different with an indoor tub. It will require less maintenance work because there are simply fewer contaminants to make their way into the tub.
Your cover will also get a lot less wear and tear when it's not exposed to the elements!
Even if they are in your backyard, outdoor hot tubs are not always private. Neighboring properties might overlook your area, leaving you exposed to prying eyes—especially from upper floors. However, you can be assured of total privacy when you install the tub indoors.
Whether warm or cold outside, you can control the temperature indoors—and this means getting to use your hot tub during any season.
Cuts down on unused space
If you have a big house, or if the kids have moved out, what can you do with the extra space? A hot tub can be a great addition to your home in one of the unused rooms to make use of the empty space.
It's more convenient to get in and out of an indoor hot tub because everything in the house will be within closer reach. Need another drink? Just grab one from the kitchen. Want to get in the shower after? It's right there.
What's more, it's safer and easier to use an indoor tub at night because you have indoor lighting. And you won't need to apply sunscreen to use your tub on sunny days either.
Problems with indoor hot tubs
While there are benefits of having an indoor hot tub, it's not all plain sailing if you don't follow certain guidelines:
A properly sanitized spa shouldn't have a strong smell, but we all know sanitizer can get out of balance sometimes.
If this happens, the odor could remain for a while—even if the room has an effective ventilation system.
High installation expenses
Installation expenses can pile up with any hot tub, but there are several extra factors to consider indoors:
- You have to find a suitable tub that can physically get into the space (this could be easier said than done depending on your doorways).
- Movers are likely to charge a premium if this counts as a difficult installation.
- Structural work (or at least analysis) will be necessary for anything that's not a concrete ground floor.
- If the floor can support the weight, you may want to install a durable, waterproof non-slip surface.
- You might also have to do some electrical and plumbing work to get power and water for filling, plus drainage, into the room.
Ventilation issues & humidity
Humidity is a big problem indoors, especially considering the water is warm and therefore evaporates faster. The room must be well ventilated and have an extractor fan to push the moisture outside before you end up with condensation which, left unchecked, could lead to damp, mold, and mildew.
One piece of hardware that can also help a lot to lower moisture levels is a dehumidifier, like this Frigidaire one which removes up to 50 pints of water per day:
You'll also need to either install moisture-proof drywall—often referred to as greenboard or blueboard because of its color—or waterproof your existing drywall to prevent the growth of mold and mildew on the walls.
Can you put an inflatable hot tub indoors?
Yes, and this might actually be a more convenient option compared to a more permanent acrylic hot tub in some ways.
For example, you could have the spa outdoors during the summer, and then just bring it inside during winter (great news for cold climates as most inflatable hot tubs can't be used in temperatures under 40°F).
If you need the space back in your house to host guests, it is easy to deflate the tub, fold it and then store it until you're ready to use it again.
However, consider these factors first:
- Although inflatable hot tubs are very lightweight compared to acrylic spas, fill them with water and add three or four people, and you still have a heavy load placing all of its weight on a small area. This means you still need to do the same structural checks as with any spa.
- An inflatable hot tub is more delicate than a hardshell spa. Therefore, wherever you decide to set it up, ensure the floor is flat, clear and even (no rough garage floors) so that it does not damage or puncture the material.
How do you maintain an indoor hot tub?
If you plan to leave the same water in the spa for more than a couple of uses, treating the water in an indoor tub is much the same process as for an outdoor spa:
- Shock and sanitize your water properly:
- Keep your filter clean with a regular cleaning schedule.
- Maintain a healthy water balance:
- pH between 7.2 and 7.8
- Total alkalinity between 80 and 140
- Calcium hardness between 150 and 250
If you're new to hot tub water chemistry, I put together a detailed guide for exactly what chemicals you need and how to use them.
Do you need a cover for an indoor hot tub?
Yes, but the purpose will not be to protect the water from leaves, wild animals, and other outdoor debris. Instead, it will keep small children or pets out, help to maintain the water temperature, and minimize evaporation.