How Much Water Does a Hot Tub Hold?

Knowing how much water a hot tub holds is vital for a few reasons. First, you must ensure the deck or surface on which the hot tub will sit can withstand the tub's weight with water and people. Second, it helps you understand how long it will take to fill your hot tub. Since this is something you will do several times a year, it is useful information. The cost of a hot tub is a significant investment, and filling it adds to the cost, so knowing how much your hot tub holds is an important factor. 

How Much Water Does the Average Hot Tub Hold?

Hot tubs come in many shapes and sizes, but the average one measures seven or eight feet per side, fits four people, and holds 300 to 400 gallons of water. Smaller hot tubs (meant to fit two people) generally contain 150 to 250 gallons, and large hot tubs (meant for entertaining up to eight people) take as much as 650 gallons of water.

4 Steps to Tell How Much Water a Hot Tub Holds

So, how do you tell how much water your hot tub requires? Here are four simple steps. 

1. Read the Manual 

The easiest way to tell how much water your hot tub holds is to read the manufacturer’s manual. Size and water capacity will likely be one of the first things listed in the manual. You can also read precautions and other important details about the hot tub. If you have misplaced your manual, check the manufacturer’s website as they usually upload them online. 

2. Contact the Manufacturer 

If you are unsure of how much water your hot tub holds and cannot find the manual, consider contacting the manufacturer. You can get contact information via email or phone if you visit their website. Since it is a question they can answer quickly, it should not take much time. 

3. Call the Store 

Most stores can tell you how many gallons of water a hot tub takes if they still have it in stock or if it is one they sell often. They may know the answer immediately without checking any information, but they will have access to more information than consumers if there is any doubt. You can also contact a hot tub installer near you if you cannot get the answer from your local store. 

4. Search the Web 

You can always try trusty Google; however, research enough to ensure you get the right answer. Since anyone can post anything online, you do not want to fall for false information and fill your tub improperly.

How to Calculate Manually How Much Water a Hot Tub Holds

Another way to determine how many gallons are in a hot tub is to calculate its dimensions yourself. This method differs depending on the tub shape and requires a tape measure.

Calculate the volume. Measure in inches from the inside of the hot tub. For a rectangular or square hot tub, multiply length x width x average depth. For a round hot tub, multiply radius squared x average depth x 3.14. Divide the number by 1,728. Then multiply by 4.8 to get the number of gallons. If there are seats in your hot tub, multiply by 3.4 instead to account for that.

To get the average depth, add the deepest part of the tub to the shallowest part and divide by two.

How Long Does It Take to Fill a Hot Tub?

The average hot tub takes one to 1.5 hours to fill up, but this varies due to tub size and water pressure. The average garden hose has a flow rate of nine to 17 gallons per minute. The faster your flow rate and the smaller your tub, the quicker the tub will fill, and vice versa. 

To determine your hose's flow rate, get a 10-gallon bucket. Time how long it takes to fill the bucket and divide the total minutes by 10 to determine the number of gallons per minute.

How Often Do You Need to Drain a Hot Tub?

On average, you should drain your hot tub once every three to six months. If you use the proper chemicals and keep the water clean, you can stretch it toward the six-month mark, but no longer or you will deplete the hot tub benefits. 

The more often you drain and refill the water, the better the chances are of keeping the hot tub clean and safe. Knowing how much water your hot tub holds can help determine how long it will take to fill it.