What Size Water Heater Do I Need for a Walk-In Tub?

Understanding walk-in tub water requirements

Walk-in tubs usually take up about the same amount of space as a standard tub — unless you buy one that’s a larger size, such as a bariatric walk-in tub or two-seater model. While you can sometimes use your existing plumbing to support a walk-in tub, other times you need to reroute your plumbing, some experts say.

For example, if you have a shower already there and you’re trying to convert it to a walk-in tub, the sizing of the plumbing and the location of hot and cold water lines can be different, explained Jamin Katzer, senior construction manager at Earth Saving Solutions, a general contracting company.

Standard tubs are typically a foot deep, while walk-in tubs are about 3.5 feet deep. This means walk-in tubs require a lot more water to fill. If your water heater has a 40-gallon tank and you have a 50-gallon tub, your hot water might run out before you’re done filling the tub. If that’s the case, you might need to purchase a larger water heater.

How much water will my walk-in tub use?

Walk-in tubs are usually the same size as standard tubs, just taller, so they use more water. If you purchase a basic walk-in tub, you can expect to use about 50 gallons of water per use. Smaller walk-in tubs designed for compact spaces might use 40 gallons, but tubs made for two people can use 120 gallons.

» MORE: What is a walk-in tub and how does it work?

Do I need to upgrade my water heater?

You don’t want to buy a walk-in tub and have it installed only to realize halfway through filling it up that you don’t have enough hot water to take a comfortably warm bath.

Knowing how big your tub is can help you figure out if your current water heater can accommodate the extra gallons. You don’t necessarily need to upgrade your water heater. Instead, look for a walk-in tub that matches your heater’s capacity.

Types of water heaters for walk-in tubs

According to the U.S. Department of Energy, there are several types of water heaters available, including:

• Storage tank heaters: These heaters hold a stored amount of hot water that is ready to use. With this type of heater, you’ll use more energy in your home if you run out of hot water before your walk-in tub fills.
• Tankless heaters: These provide hot water only as necessary and don’t have a storage tank. If you have the correct size for your walk-in tub, you shouldn’t run out of hot water with a tankless heater.
• Heat pump water heaters: Similar to tankless heaters, this type of heater can be more energy-efficient, saving you money by pumping heat from one place to another instead of producing the heat directly.
• Solar water heaters: These use energy from the sun to provide hot water, saving you money in energy costs.

Factors to consider when choosing a water heater size

When selecting the right water heater size for your walk-in tub, there are several important factors to consider:

• Walk-in tub capacity: Different models have different capacities, ranging from 40 to 120 gallons. Be sure to check the exact water volume your tub requires and ensure your heater can deliver enough hot water for a full fill.
• Household water usage: If others in your home will be using hot water at the same time — for showers, laundry or dishwashing — you’ll need a water heater that can handle multiple demands without running out of hot water.
• Water heater recovery rate: This is the amount of hot water a heater can produce per hour. A higher recovery rate helps ensure consistent hot water availability during longer or repeated baths.
• Energy efficiency: Look for energy-efficient models that suit your needs, such as tankless or heat pump heaters, which can save on utility costs while still providing enough capacity.
• Bathroom location and plumbing layout: Longer distances from the heater to the tub and complex plumbing layouts can impact how quickly and efficiently hot water reaches your tub.

Bottom line

Look at your home’s water heater before purchasing a walk-in tub to make sure it can accommodate enough hot water for the increased size. You may need to upgrade your water heater if it’s too small.

» COMPARE: Best Walk-In Tubs