How Much Water Does a Hot Tub Hold?

A hot tub, also known as a spa or jacuzzi, is a luxurious way to relax and unwind at home. 

The soothing, heated water provides hydrotherapy benefits as the jets massage away tension. But have you ever wondered just how much water goes into filling up one of these large tubs?

Here we’ll explore the factors that determine hot tub water capacity and provide averages for different tub sizes.

Typical Hot Tub Dimensions

The first thing that impacts how much water a hot tub holds is simply its physical size and shape. Hot tubs come in many different dimensions, but some typical sizes include:

Two-Person Hot Tubs

• Length: 5-6 feet
• Width: 5-6 feet
• Height: 3-4 feet

Two-person hot tubs are compact and fit well in small backyards. Their cozy size is perfect for couples.

Four-Person Hot Tubs

• Length: 6-7 feet
• Width: 6-7 feet
• Height: 3-4 feet

Four-person hot tubs comfortably fit small groups. This size is popular for families.

Six-Person Hot Tubs

• Length: 7-8 feet
• Width: 7-8 feet
• Height: 3-4 feet

Six-person hot tubs are a middle-ground size, suitable for entertaining. They provide ample room to stretch out.

Eight-Person Hot Tubs

• Length: 8-9 feet
• Width: 8-9 feet
• Height: 3-4 feet

Eight-person hot tubs are quite spacious. They work well for larger gatherings and parties.

As you can see, the length, width, and height all increase with the tub’s capacity. This directly corresponds to how much water the tub can hold.

Calculating Hot Tub Water Capacity

Hot tub manufacturers usually provide the total gallon capacity in the product specs. But you can also estimate the water amount using the tub’s dimensions. Here’s a simple formula to calculate approximate water capacity:

Gallons = (Length x Width x Average Depth x 7.5) / 231

Where:

• Length/Width are the interior tub dimensions in feet
• Average Depth is 2-4 feet
• 7.5 is the number of gallons in a cubic foot of water
• 231 is the number of cubic inches in a gallon

Let’s break this down for a typical 6-person hot tub measuring 7 x 7 x 3 feet:

• Length: 7 feet
• Width: 7 feet
• Average Depth: 3 feet

Plugging this into the formula:

Gallons = (7 x 7 x 3 x 7.5) / 231 = 315 gallons

So this 6-person hot tub holds approximately 315 gallons of water.

You can use this same formula to estimate the capacity of any size hot tub by inputting its dimensions.

Average Water Capacity by Hot Tub Size

Now that we’ve covered how to calculate hot tub water volume, here are some general averages:

Two-Person Hot Tubs

• Hold 150-200 gallons on average

The small footprint of two-person hot tubs equates to lower water capacity. But the cozy size still provides a luxurious soak.

Four-Person Hot Tubs

• Hold 250-350 gallons on average

Four-person hot tubs have more interior space, allowing for about 100 additional gallons over two-person tubs.

Six-Person Hot Tubs

• Hold 300-400 gallons on average

Six-person hot tubs are a popular middle-ground size with ample room to stretch out. Their water capacity jumps up to handle more bathers.

Eight-Person Hot Tubs

• Hold 350-450 gallons on average

The most spacious eight-person hot tubs top out around 450 gallons for the largest designs. More interior room means more water.

Factors That Impact Hot Tub Water Capacity

A few other factors beyond just size can influence how much water a hot tub holds:

Shape

Round hot tubs are extremely efficient at fitting bathers in a compact footprint. However, square and rectangular tubs maximize every inch of interior space. These shapes may fit more gallons in an equivalent overall dimension.

Number of Jets

More jets at different angles deliver better hydromassage. But they also displace interior space that could otherwise hold water. Hot tubs with minimal jets may fit 5-10 more gallons.

Seating Layout

Built-in seats are comfortable, but they also take up space. Some hot tubs maximize capacity by using flat benches or open layouts instead.

Plumbing Components

Heaters, pumps, filters, and control packs all demand space. Newer hot tubs are engineered to consolidate these components, creating more room for water.

Other Factors Impacting Total Water Volume

A few other considerations beyond just the tub capacity factor into the total water volume:

Piping

The plumbing lines that feed the hot tub require extra water to prime and operate correctly. This might account for 10-15 gallons.

Filter

Water circulates through an external filter to keep it clean. The filter housing itself holds some water that is included in the total.

Plumbing Components

Small amounts of water fill the heater, pump, chlorinator, and other gear. Every gallon counts toward the total.

When accounting for these additional components, expect the complete water volume to be 15-20 gallons more than just the shell capacity.

Maintaining Proper Water Levels

With up to 450 gallons of water on board, monitoring and maintaining water levels is crucial for safe operation and efficient heating:

• Check water levels weekly and top off as needed. The water should fully cover jets and skimmers.
• Add water if the level drops more than 2-3 inches due to splashing or evaporation.
• Avoid overfilling beyond the tub’s rim, as water may spill out when bathers enter.
• Drain and refill 3-4 times per year as part of routine maintenance.

Proper water levels ensure your hot tub provides relaxing hydrotherapy all year long!

Operating Costs of a Hot Tub Based on Water Capacity

Once you know how much water your hot tub holds, understanding the operating costs is helpful for budgeting. Here are the main costs associated with running a hot tub based on its water volume.

Heating Costs

The #1 operating cost for a hot tub is heating the large water volume. Plan for the following energy usage:

Electric Hot Tubs

• Use 3-5 kW of power to heat water
• Cost ~15-25 cents per hour to operate (varies on electricity rate)
• Monthly cost of $30-60 typically

Gas Hot Tubs

• Use 40,000-50,000 BTU burners
• Cost ~50 cents – $1 per hour in natural gas
• Monthly cost of $30-60 typically

Larger hot tubs with more water capacity will be toward the upper end of these ranges. Well-insulated covers and lower temperature settings can reduce energy use.

Water Costs

Filling a hot tub’s hundreds of gallons adds up in water expenses:

• Typical water rates range from $3-6 per 1000 gallons.
• Filling a 400 gallon hot tub costs $1.50 – $3 per change.
• With 4-5 changes per year, expect $10-15 in annual water expenses.

Proper water maintenance extends time between draining, minimizing costs.

Chemical Costs

Sanitizers, balancers, and shock treatments are needed regularly:

• Hot tubs use $2-4 per month in chemicals normally.
• Larger water volumes may approach $5-6 per month.
• Annual chemical costs are $30-50 typically.

Testing water frequently avoids overuse of chemicals.

Filter Cleaning

Dirty filters reduce water quality and chemistry. Plan for:

• Monthly deep cleanings of the filter
• Filter cleaner sprays costing $10-15 per year
• New replacement filters every 2-3 years for $50-75.

Extending Time Between Draining a Hot Tub

Draining and refilling a hot tub’s hundreds of gallons of water 3-4 times per year can become tedious and expensive. Here are tips to safely extend time between complete hot tub drains.

Continue Proper Water Chemistry

Maintaining proper sanitizer, pH, and alkalinity levels keeps water clean and free of contaminants. This allows extending time between drains.

Test and Adjust Chemistry Weekly

Check chlorine or bromine, pH, and alkalinity with test strips. Make minor adjustments as needed.

Shock Treat Water Regularly

Kill bacteria and prevent algae growth with weekly shock treatments.

Replace Cartridge Filters Monthly

Dirty filters rapidly reduce water quality. Swap cartridges monthly.

Use a Hot Tub Ozonator

Ozone generators help keep water crystal clear for 4-6 months between drains. The extra sanitation fights contamination. Models starting around $300 represent a worthwhile investment.

Scrub Interior Surfaces

Buildup of oils, cosmetics, and dirt occurs over time. Every 2-3 months, drain a few inches of water and use a hot tub surface cleaner to scrub the interior. This tackles hidden grime. Refill with fresh water after scrubbing.

Drain and Refill After Heavy Use

Major hot tub parties or periods of frequent use create extra contaminants. Drain and refill after 7-10 days of consistent heavy bather load.

Replace Water Partially

Rather than a complete drain, replace 25-30% of water monthly. This adds some fresh water to lower contaminant levels. It also makes draining easier by doing smaller volumes.

Clean or Replace Plumbing

Scale buildup inside pipes or heaters will gradually shed into water. Keep plumbing sparkling by descaling annually or installing new plastic pipes every 4-5 years.

Choosing Hot Tub Jets and Pumps

Powerful pumps drive streams of heated, jetted water that provides therapeutic massage. Here’s what to consider when choosing hot tub jets and pumps:

Types of Jets

Jets come in a variety of styles that offer different massage experiences.

Directional Jets

• Provide targeted streams of pressurized water
• Feel invigorating and allow aiming massage at specific muscles
• Come in rotating and stationary models

Rotating Jets

• Feature two nozzles that continuously rotate
• Offer wide massage coverage for neck and back

Waterfalls

• Gentle water flows for light massage
• Help set a tranquil ambiance

Air Jets

• Mix air bubbles into water flow
• Feel effervescent for gentle, bubbly massage
• Locate along seats and floor

Jet Pressure

Higher pump power increases jet pressure:

• 50-60 PSI for mild, soothing massage
• 60-80 PSI provides moderate intensity
• 80+ PSI offers strong, deep tissue massage

A range of pressures caters to different preferences.

Adjustable Jets

Movable jets allow aiming water flow:

• Ball joint jets offer multidirectional adjustment
• Rotating faceplate jets swivel open/closed
• Massage pattern jets select various stream options

Adjustability accommodates different body positions and heights.

Jet Placement

Optimal jet positioning ensures full-body coverage:

• Neck and shoulder jets locate above seats
• Back jets align vertically along the wall
• Calf and foot jets install on the floor

A design with at least 6-8 jets ensures adequate coverage.

Jet Styles by Seat

Varying jet styles creates unique massage zones:

• Neck massage jets for loungers
• Rotating back jets behind primary seats
• Effervescent, bubbly jets for bench areas

Pumps

Pumps propel water through the jets. Performance factors:

• Horsepower – 2-3HP for most tubs
• Number of speed settings – dual or multi-speed pumps offer customization
• Maximum flow rate – 50-100 GPM
• Specialized neck/shoulder pump – provides light massage

Look for name-brand pumps like Balboa or Cal Spas for reliability. And ensure pumps match jet count/placement to power all positions.

With the right jets and pumps providing strong, invigorating massage, a home hot tub delivers spa-quality relaxation. 

Carefully planning jets and performance creates a hydrotherapy experience perfect for unwinding.

Shopping Considerations When Buying a Hot Tub

Purchasing a hot tub is an exciting investment that requires careful shopping. Here are top considerations for choosing the best value hot tub to match your needs and budget.

Hot Tub Size

Available sizes include:

• 2-person (seats 2-3 adults)
• 4-person (seats 4-5 adults)
• 6-person (seats 6-7 adults)
• 8-10+ person (seats 8-10+ adults)

Choose adequate seating for the number of people in your household plus occasional guests. Also factor in physical dimensions that will fit your available space.

Hot Tub Shape

Common hot tub shapes:

• Rectangle – efficient use of space
• Square – provides open seating
• Round – fits small areas, creates intimacy
• Oval – maximizes stretched-out lounging

Consider the seating arrangement and number of positions needed when choosing a shape. Oval and rectangle maximize space efficiency.

Jet Styles, Placement, and Performance

Look for a variety of directional and rotational jets located throughout the tub. Floor jets should be included for full-body massage. Performance factors:

• Total number of jets – 20+ is optimal
• Jet pump size – minimum 2HP, up to 3HP
• Custom jet options – adjustable directionals, flow rate variances

Higher jet count and more pump power provide stronger water flows.

Materials and Durability

Hot tub shells are commonly made from either acrylic or rotationally-molded polyethylene.

• Acrylic – glossy, plastic-like, amenities like integrated cupholders
• Polyethylene – matte finish, very durable but fewer special features

Cabinet materials include synthetic wood composites or marine-grade polymers. Both offer weather and moisture resistance.

Additional Features

Optional amenities to enhance enjoyment:

• Multi-color LED lighting packages – set underwater mood lighting
• Integrated waterfalls – tranquil cascading water flows
• Stereo systems – set the musical ambiance
• Ozone sanitation – maintains cleaner water

Consider options that match your priorities for creating a personalized backyard oasis.

Energy Efficiency

Ways to maximize efficiency and reduce operating costs:

• Well-insulated locking cover
• High-density foam cabinetry
• Programmable heating cycles
• Upgrade to full foam or plastic shell insulation

Energy savings may justify slightly higher purchase costs.

Warranty

As a major investment, protect your purchase with a strong warranty:

• Lifetime warranty on shell – Acrylic or polyethylene tub should have lifetime warranty.
• 2-5 years parts – Pump, heater, control system should have minimum 2-5 year warranty.
• 1-2 years labor – Free service calls for 1-2 years.

Read warranty details carefully and only buy from an authorized dealer.

Budget

Final costs are impacted by size, features, accessories and additional fees.

• Entry-level acrylic hot tubs – Around $4,500 to $7,000
• High-end customized hot tubs – $10,000 to $15,000+
• Consider installation fees if not DIYing.

Spend time reviewing different models to find the best options matching your budget. Focus on quality over frills.

FAQ About Hot Tubs

Get answers to the most common questions about hot tubs with this helpful FAQ!

How Much Does A Hot Tub Cost?

Basic hot tubs start around $4,500. High-end models with maximum features and customization can cost $15,000+. Average cost is $7,000 to $12,000.

How Long Do Hot Tubs Last?

With proper maintenance, a quality acrylic or polyethylene hot tub will last 15-20 years. Replace components like pumps every 5-10 years as needed.

What Is Better – Acrylic Or Plastic Hot Tubs?

Acrylic shells have a glossy finish and more color options. Plastic polyethylene shells are extremely durable. Performance is similar if properly maintained. Acrylic tubs typically cost a bit more.

Do Hot Tubs Consume A Lot Of Water?

The water in a hot tub is recirculated and reused for months between complete draining/refills. The water loss from splashing and evaporation is fairly minimal and only requires topping up every couple weeks. Overall water usage is low.

How Often Should You Drain And Refill A Hot Tub?

Plan to fully drain and refill your hot tub every 3-6 months. More frequent water changes may be needed with heavy bather load. This maintains clean and sanitary spa water.

Final Thought

With hundreds of gallons of water requiring heating and maintenance, hot tubs represent a significant investment. But the relaxation and therapeutic benefits make it worthwhile for many homeowners. 

Carefully considering size, features, operating costs, and maintenance requirements allows you to make an informed hot tub purchase. Proper care results in years of hydrotherapy enjoyment.