How Often Should You Add Water To Your Hot Tub?

Jacuzzi, J-385, Filling A Hot Tub

Have you ever had so many people in a hot tub that the water started to pour over the sides? When the party was over and the hot tub was empty the water level was probably noticeably lower. What about turning on the jets only to see water spraying out of the hot tub?

As a general rule, you shouldn’t have to add water to your hot tub more than once a month. You should check the water level of your hot tub every time it is used or at least once a week and add water if needed. The water level should stay above the highest jet or the minimum water line defined by the manufacturer.

There is a lot more to talk about when it comes to adding water to a hot tub so let’s get into it.

How Can My Hot Tub Lose Water?

There are multiple scenarios that cause the water level of your hot tub to drop. A gradual lowering of the water level with regular use is normal, but a rapid decrease or a large decrease without any usage could point to a problem.


It is hopefully no surprise that a hot tub contains hot water, usually between 98 and 104 degrees (F). The warmer the water the faster it will evaporate. This is because the water molecules move faster as temperature increases which makes it easier for them to gain enough energy to turn from a liquid to a gas. Evaporation also depends on the temperature of the air, air movement, and humidity. The higher the air temp, the lower the humidity, and the more air movement across the surface of the water, will all increase the evaporation rate.

Leaving the cover on your hot tub will significantly reduce evaporation, however, there are times when the cover will be off for extended periods of time. For example, when you are using the hot tub or when you are performing routine water maintenance such as shocking the hot tub. (Which should be done fairly often as described in my article)

When you lift the cover off a hot tub, a bunch of condensation will drip back into the water. This is a good thing as it means your cover is trapping the water vapor and preventing evaporation loss. Unless you are leaving the cover off for longer than normal use would require, you should see very little evaporative effect on your hot tub water level.


A hot tub that is quickly losing water, or loses water with the cover on and little to no usage is suspect for having a leak. A large leak should be noticeable by pooled water in or around the cabinet of the hot tub. Unfortunately, a smaller leak may take a while to show itself because most of the water will be absorbed in the insulation foam filling most of the hot tub cabinet interior.

For a large leak, you should see the water level in your hot tub drop quickly. How quickly depends on the size of the leak, but if your water level drops noticeably between uses or more than an inch a month, you probably have a leak.

A small leak will be more subtle but may present itself as a steady but slow drop in water level. This would be an abnormal water level change. After a few months of usage, you should start to understand your normal water loss based on your usage. If the water loss increases suddenly or increases for an extended period of time, without a significant increase in usage, then you could have a small leak.


When you enter your hot tub, your body will displace the amount of water equivalent to your mass. The water level rises as a result of this displacement. Hot tubs are designed to handle this displacement for its rated number of bathers. If you have a party with many bathers or kids that like to jump and splash you could end up having water spilling over the sides of your hot tub.

For the most part, this does not present as a major issue, and who doesn’t like to entertain in their hot tub. But, if too much water is dumped, you will need to add more water to the hot tub to replace the loss. Make sure to check the water level any time you experience one of the above-mentioned scenarios.

General Use

Every time you use your hot tub you are carrying water out on your body, in your clothing and even a small amount is absorbed into your skin. Over time, this can start to add up. Think about the last time you wrung out your swimsuit. It leaves a not-insignificant amount of water pooled on the floor.

Compared to the 300 to 500 gallons of water in your hot tub this may seem trivial, but if you use your hot tub every day as I do, then over time this will start to add up.

How Often Do I Need To Add Water To My Hot Tub?

Hose Filter, Jacuzzi, J-385 Filter Well, Filling Hot Tub

Now you know what can cause your hot tub to lose water. You know when you need to check the water level in your hot tub. But how often do you need to add water?

If you haven’t guessed it, the answer is it depends. I mentioned at the beginning of this article that you shouldn’t have to add water to your hot tub more than once a month and that still holds true on average. But, if you use your hot tub more than average, have large parties, have a leak, or live in a warm and dry climate, you may have to add water to your hot tub more often than once a month.

If your hot tub has a light bather load, always has the cover on, or you live in a humid climate, then you may never have to add water to your hot tub between your routine drain and fills.

So what is the general rule of thumb then? You should add water to your hot tub when the water level drops below the highest jet, or the minimum fill line defined by the hot tub manufacturer. This way you always maintain the optimal level of water in your hot tub.

How Can I Make My Hot Tub Water Last Longer?

Here are some tips to help make your hot tub water last longer.

  • Start with clean and fresh water
  • Purge your hot tub with a plumbing cleaner
  • Maintain proper chemical balance
  • Clean filters weekly
  • Deep soak filters monthly
  • Shock the water regularly
  • Use a mineral based water care system
  • Use an enzyme based water care system
  • Add a salt water system
  • Rinse off before using the hot tub

Start With Clean And Fresh Water

Your hot tub water will always be at its best after a fresh fill. Starting with fresh water will make your water care routine much simpler. It is recommended to use a pre-filter on your garden hose to remove metals, minerals, and contaminants from your water. You should do this even if you are on city water. Also, make sure to never fill your hot tub with softened water.

Even better would be to deep clean your plumbing with a good purge product which I will talk about next.

Purge Your Hot Tub With A Plumbing Cleaner

A good purge will remove biofilm build-up from the hot tub plumbing lines, jets, and other surfaces. Biofilm is a layer created by bacteria that allows it to flourish while being protected from harm from your sanitizer. With excessive biofilm, it will be harder to maintain the water quality in your hot tub and your sanitizer will work less efficiently.

Purging your hot tub before each drain and fill will remove the biofilm making your next fill easier to maintain and last longer.

The product I use is called Ahh-Some – Hot Tub Cleaner. It comes in three size containers Ahh-Some 2oz, Ahh-Some 6oz, and Ahh-Some 16oz. The 2oz container lasts two purges with my 500-gallon hot tub. It is amazing the amount of gunk it gets out of the plumbing lines.

Another product that I have not used but know a bunch of other hot tub owners like is called Oh Yuck Healthy Hot Tub Cleaner. I have heard this product works well and is a bit cheaper than Ahh-some, but I do not have personal experience with it.

Maintain Proper Chemical Balance

Maintaining the proper chemical balance in your hot tub water will make your sanitizer more efficient, prevent the build-up of organics in the water, and allow you to use fewer chemicals in general. Over time the water will become saturated with total dissolved solids and will become unstable. Maintaining a good chemical balance will help to lengthen this process and allow your water to last longer.

Clean Your Filters Weekly

You should clean your filters regularly to keep them working at optimal efficiency. This will make your filters last longer and keep your water fresh and clean for as long as possible. You should check out my article on filter maintenance if you are interested in learning more.

Deep Clean Your Filters Monthly

A weekly rinse will keep your filters running smoothly, but a deep soak once a month in a good filter cleaner will extend the life of your filters saving you money. A deep clean will also remove oils and organic buildup that a simple rinse cannot reach. This will reset your filters so they don’t become saturated helping to keep your water fresh and clean.

You can use your filter cleaner of choice, but if you are looking for one, Spa Depot Power Soak is the #1 rated cleaner on amazon.

Shock The Water Regularly

You should shock your hot tub water at least once a week with a good quality shock product. I use a non-chlorine-based shock product in my hot tub. The purpose of spa shock is to oxidize the organics in the water which off-gasses the chloramines and bromamines freeing up your sanitizer to do its job again. This will make your water last longer.

If you are interested in learning more, I wrote an article on Shocking A Hot Tub, that will teach you how often, what types of shock to use, and how to shock a hot tub.

Use A Mineral Based Water Care System

Mineral-based water care systems dissolve minerals in the water that make it easier for your sanitizer to do its job and ultimately make your water care routine simpler. Using a mineral system allows you to bring your sanitizer level down to as low as 1.0 ppm which if you have sensitive skin like me, will make you feel much better about soaking in a hot tub.

There are a few systems on the market, but the number 1 rated system is called AquaFinesse. This product is raved about by its users and can make your water last much longer.

I currently use a Jacuzzi branded mineral cartridge in my hot tub.

Use An Enzyme Based Water Care System

Like a mineral-based water care system, an enzyme system helps your sanitizer be efficient. It works by using enzymes to break down the organics in the water so they can be destroyed by your sanitizer. These systems can drastically increase the life of your hot tub water because they are literally eating the organic waste out of the water.

Another added benefit is you can drastically reduce the amount of sanitizer in your tub to levels as low as 1.0 ppm because your sanitizer will work so efficiently.

There are a few systems on the market, but the number 1 rated system is called Spa Marvel. I do not use this product currently but will likely be switching to it in the near future based on the feedback I have gotten from the hot tub community.

Add A Salt Water System

A saltwater system uses salt to generate chlorine through a process called electrolysis. This maintains a constant level of chlorine in the water which keeps the unwanted nasties at bay 24/7. Hot Spring is the largest hot tub manufacturer that sells an onboard saltwater system. Users of them claim they only have to change their water once every 1-2 years. This still requires proper water maintenance but could be a good option for you.

There are retrofit products available but a built-in system will be the easiest if you are in the market for a new hot tub. The replacement salt cartridges can be expensive.

Rinse Off Before Using Your Hot Tub

This may seem like an extreme measure, but how many times have you had a party where the next day your hot tub is cloudy and foamy? The main cause for this is all the oils, lotions, and soaps that your hot tub bathers bring into the hot tub with them on their bodies and clothing. Some of these will dissolve into the water and add to the total dissolved solids in the water which will reduce its life.

Rinsing off before entering the hot tub will remove most of the contaminants that you can introduce into the hot tub water. Ultimately this will make your hot tub water last longer.

Do You Fill A Hot Tub Up With Cold Water?

As a general rule, a hot tub should only be filled with cold water. Scalding hot water can damage the acrylic shell of the hot tub or other parts that are only meant to withstand water temperatures much lower than a normal hot water tank produces.

Using anything other than cold water when filling your hot tub is not worth it.

When subjected to extreme temperature changes, the layers of a hot tub shell can expand and contract rapidly which will weaken the structure. This increases the risk of cracking and premature failure. Extreme temperatures can cause bubbling and/or blistering of the hot tub shell surface.

The hot water tank in my house holds 50 gallons of water. My hot tub holds 500 gallons. That is a 10x difference in volume that makes trying to fill my hot tub using hot water inefficient. I would quickly run out of hot water and would most likely only raise the final water temperature by a few degrees.

If you have a hard water supply as I do, then you will have a whole house water softener. Generally, the only things not connected to the softened water are the exterior hose bibs. This means using hot water to fill your hot tub will be adding softened water which can cause long-term damage to the components of your hot tub.

It may be possible to use warm water (a combination of cold and hot) to fill your hot tub as long as it isn’t softened. But because of the size of your hot water tank, this is still inefficient. Just let the hot tub warm up the water as it is designed.

How Many Buckets Does It Take To Fill A Hot Tub?

I am not sure why you would want to fill a hot tub with a bucket, but if you did, this is what it would take.

In total, it should take 300 1-gallon buckets, 100 3-gallon buckets, and 60 5-gallon buckets to fill an average size (300 gallons) hot tub. This amount will vary based on the size of the bucket and the volume of the hot tub that is being filled.

I own a Jacuzzi J-385 which holds about 500 gallons of water, so you can see from the table below that it would take a lot of buckets to fill.

Hot Tub Size1 Gallon Bucket3 Gallon Bucket5 Gallon Bucket
Small (100 gallons)10033 1/320
Medium (300 gallons)30010060
Large (500 gallons)500166 2/3100
Number of Buckets per Hot Tub Size

Remember, a gallon of water weighs 8.33 lbs. So a 1-gallon bucket weighs 8.33 lbs, a 3-gallon bucket weighs about 25 lbs, and a 5-gallon bucket weighs about 42 lbs.

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