How High Should a Hot Tub Be Filled?




Hot tubs are complicated and expensive pieces of equipment that require proper use and maintenance to keep them in working condition. 

One particularly important thing is the hot tub water level. If there is too much or too little water, you risk damaging the sensitive equipment that keeps the hot tub running. 

Unfortunately, despite this important fact, many hot tubs still come without proper indicators to show what the appropriate water level for the tub is.

How High Should a Hot Tub Be Filled

How much water should you put in a hot tub?

The amount of water you put in a hot tub is extremely important. 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 then water cannot be drawn in through there and air is likely to be drawn into the system which can damage the pump and may also damage the heater.

If the hot tub water level is above the opening of the skimmer then the skimmer will no longer be able to draw in any contaminants and debris floating on the surface of the water.

Why a hot tub water level fluctuates

Firstly, the hot tub water level drops due to evaporation with time. This is especially true if the hot tub is in operation for long 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 the water will cool down quickly too. If you need a hot tub cover you can buy one specifically for your model at Florida Spa Covers (who ship throughout the US).

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

Finally, there is the chance that the hot tub may be installed improperly or damaged, and 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 every day, there might be a leak that needs 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

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 simply 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

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

Bodies displace water (I blame Archimedes) and that is really noticeable in a hot tub.

If the hot tub level is say 2-3 inches above the highest jet before anyone gets in, then you will probably find that it is overflowing before the 6th person gets in.

Some years ago, when I had my first hot tub, I invited some friends around 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, 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 leading to the hot tub becoming inoperable and requiring repairs. 

What happens if hot tub water gets too low?

What happens if hot tub water gets too low

Going back to my hot tub party described above, the opposite happened once it was 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 of water 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 some 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, if the water level is above the intakes but only an inch or so above, rather than the 2-3 inches recommended, the jets may not operate at optimum pressure and standards, resulting in a sub-par hot tub experience. 


With all these factors considered, it becomes evident that watching the water level and topping up the hot tub water level when required should be a regular part of the hot tub’s maintenance schedule.


What happens when 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. If the hot tub is indoors then the water could damage the floor covering.

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 a significant amount ie. so that the water level gets close to the bottom of the skimmer opening or to the highest jets.