How High Should a Hot Tub Be Filled?




Maintaining the correct water level in your hot tub is crucial for optimal performance and the longevity of your hot tub’s equipment. Understanding how high to fill a hot tub and what to do if the water level is too high or too low is essential for any hot tub owner.

Well, we’ll be going over:

  1. The ideal water level for a hot tub and how to determine it.
  2. The implications of having too much or too little water in your hot tub.
  3. Tips for maintaining the correct water level and what to do in case of fluctuations.

Let’s dive in and explore how to manage the water level in your hot tub correctly, ensuring a safe and enjoyable hot tub experience.

How High Should a Hot Tub Be Filled
How high to fill hot tub with water

How much water should you put in a hot tub?

The amount of water you put in a hot tub is significant. Adding too much or too little can drastically alter your experience. You can buy the best hot tub and have a lackluster experience because of an unsuitable water level.

Generally speaking, the waterline should reach approximately halfway up the skimmer opening. This will usually also be 2-3 inches above the highest jet.

If the water level is below the skimmer opening, water cannot be drawn in there, and air will likely be drawn into the system, damaging the pump and the heater.

If the hot tub water level is above the skimmer’s opening, the skimmer can no longer draw in any contaminants and debris floating on the water’s surface.

Why a hot tub water level fluctuates

Firstly, the hot tub water level drops with time due to evaporation. This is especially true if the hot tub operates for extended periods where the additional heat in the water will speed up the evaporation process.

If a hot tub is outside and you don’t use a hot tub cover, then this will be very noticeable. Not only will water evaporate quickly, but it will cool down quickly, too.

Secondly, as people enter and leave the hot tub, much water will be naturally lost because it spills out. 

Finally, there is the chance that the hot tub may be installed improperly or damaged; hence, there is a small or moderate leak, reducing the water level over time. 

Your water level may decrease faster than it should due to a leak. The way to spot this is to note the frequency of the top-ups compared to the amount of use. If you only use your hot tub occasionally, yet somehow, the water level drops daily, a leak might need attention. 

The easiest way to try and detect this would be to open up one or more of the side panels and see if anything is wet. Everything inside the hot tub should be dry.

When to top up a hot tub

correct hot tub water level
How full to fill hot tub

There is no need to obsess about the water level in a hot tub.

There is no exact level that a hot tub should be filled to. Provided when the bathers are in it, the water is not likely to overflow, and when the hot tub is empty of bathers, the water level is above the highest jets by an inch or so, then that is ok.

If you need to top the hot tub up, most people use a garden hose as hot tubs do not have a plumbed in water source.

Once you have topped it up, you should check the water using a suitable hot tub test strip or other water testing method and add any chemicals that may be necessary.

What happens if hot tub water is too high?

What happens if hot tub water is too high
Hot tub water is too high

Firstly, the water level in a hot tub varies, depending on the number of people that use it simultaneously. So, the correct starting water level for one person using it will be higher than before 6 people started using it.

Bodies displace water (I blame Archimedes), which is noticeable in a hot tub.

If the hot tub level is 2-3 inches above the highest jet before anyone gets in, it will probably overflow before the 6th person gets in.

Some years ago, when I had my first hot tub, I invited friends for a hot tub party. The water level was just above the highest jet (the normal level for when my wife and I used it).

By the time the 4th person got in, it was dangerously close to overflowing (and it was in our inside garden room), so I had to start bailing with a bucket and throwing the water out of the door. I kept going with the bucket for 10 minutes before all 8 people, myself included, could get in safely.

The potential problem is, should a hot tub overflow, there is a risk that the water will get into places it is not meant to go, ie. inside the hot tub casing. In the worst case, this can result in a short circuit, making the hot tub inoperable and requiring repairs. 

What happens if hot tub water gets too low?

What happens if hot tub water gets too low
How full should a hot tub be

Returning to my hot tub party described above, the opposite happened once we decided we should all get out. Everyone stood up, which immediately lowered the water level due to the decreased displacement of their bodies.

As the hot tub pump was still on its highest setting, when the higher jets suddenly found themselves above the water level, they shot jets out of the hot tub and across the room.

If the water level in the hot tub is too low and the machine is turned on, it can lead to serious issues. This is because a water level that is too low might mean that the filters and jets take in the air instead of water. This can result in overheating and damage to these sensitive components. In the long run, this could mean that the hot tub components must be replaced. 

Additionally, suppose the water level is above the intakes but only an inch or so above, rather than the 2-3 inches recommended. In that case, the jets may not operate at optimum pressure and standards, resulting in a sub-par hot tub experience. 


A hot tub should be filled to a level where the water reaches approximately halfway up the skimmer opening or 2-3 inches above the highest jet. This ensures proper water circulation and prevents hot tub equipment damage. Overfilling can cause overflow and potential damage, while underfilling can lead to air intake, overheating, and damage to the jets and filters. Regular monitoring and topping up the water level are important for optimal hot tub performance and maintenance.

Read: We show you how to fill a hot tub


What happens when the hot tub overflows?

When a hot tub overflows, the water could get into the area underneath the tub and cause a short circuit and damage to the hot tub’s equipment. The water could damage the floor covering if the hot tub is indoors.

How much water does a hot tub lose per day?

If a hot tub is outside, not covered and the weather is warm and windy a hot tub could lose as much as an inch per day. If the hot tub is kept covered when not in use then little water should be lost due to evaporation.

How often do you add water to hot tub?

You should add water to the hot tub whenever the water level drops significantly so that the water level gets close to the bottom of the skimmer opening or the highest jets.

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