What size water heater do I need for a walk-in tub? For most homes the answer is a 75 gallon or larger tank, because a walk-in tub holds more water than many standard bathtubs and you want it filled hot before you settle in. Ella's Bubbles recommends the maximum capacity water heater available for your house, anything less than 75 gallons is not recommended, and the largest models such as the ShaK and the Big4Two may call for a dedicated large heater in addition to the one serving the rest of the home. One important point up front: the in-line water heater included with hydro massage tubs maintains your bath temperature while the hydro pump runs, but it never raises the temperature, so your house water heater does all the work of filling the tub hot. This article walks through the factors that matter, the sizing recommendations, tankless options and where to find your tub's exact water capacity.

Watch: Hot Water Capacity and Supply

Key points from the video:

• We recommend the maximum capacity hot water heater available for your house. Anything less than 75 gallons is not recommended.
• With the water demands of modern homes, a professionally installed high capacity water heater gives you consistent, constant hot water delivery, especially for our larger tubs such as the Big4Two or the ShaK.
• To check your tub's needs, visit the Compare Ella Walk-In Tubs page on ellasbubbles.com and click Compare Specs to see water capacity in gallons, both occupied and unoccupied.
• Consider a dedicated hot water supply system just for the walk-in tub, or a combination of two systems, and always consult your installer or a professional plumber.
• We recommend 3/4 inch supply lines with easily accessible shutoff valves. Ella 2-piece and 5-piece fast fill faucet sets include 5 foot supply lines.

The Factors That Determine Your Water Heater Needs

Every home is different, so there is no single answer that fits everyone. These are the factors that affect fill time and water temperature:

• The size of the walk-in tub, meaning its occupied water capacity in gallons
• The water pressure in your house
• The supply piping size and configuration, for example 1/2 inch versus 3/4 inch
• The distance from the walk-in tub to the water heater
• The faucet on the tub, fast fill versus standard
• The efficiency and capacity of your water heater
• Whether other plumbing fixtures run at the same time

The supply side of that list is covered in water supply lines, shut-off valves and pipe size, and what a realistic fill looks like is in fast-fill faucet expectations.

Our Sizing Recommendations

• Average size walk-in tubs: most homes need to replace a smaller existing heater with a 75 gallon or larger water heater.
• Our largest models, such as the ShaK and the Big4Two: these may call for a dedicated large water heater in addition to the one already serving your house.
• Tankless water heaters: electric and natural gas high efficiency tankless heaters can work, but they usually fill more slowly, so choose the highest flow rate available, 11 GPM or higher. A small on-demand unit rated at only a few gallons per minute will feel far too slow with a fast-fill faucet.

It is always recommended to upgrade toward the larger size once all the factors are considered. Please consult an experienced professional contractor to assess your home and recommend the best solution. For assisted bathing configurations, Ella also offers a fast fill water tank of roughly 105 gallons as a dedicated pre-heated reservoir, the system used on the HomeCare 32x60 transfer tub; our team can tell you whether it fits your project.

How to Find Your Tub's Water Capacity

Every Ella walk-in tub lists its water capacity in gallons, both occupied and unoccupied, on its specification sheet and on the compare specs tool at ellasbubbles.com. Your occupied capacity is the practical number for hot water planning, since the bather displaces part of the volume. As a guide, the Elite holds about 75 gallons empty and 35 to 55 gallons with a bather, the Monaco about 55 to 85 gallons occupied, the Ultimate about 95 gallons empty and 55 to 85 occupied, and the Big4One about 75 to 100 gallons occupied. The complete list is in the water capacity guide by model. Make sure your hot water supply covers the tub plus the other fixtures and appliances in your home.

What the In-Line Heater Does and Does Not Do

Tubs with the hydro massage option include an in-line water heater. It is designed to maintain the temperature of the water already in the tub, and it only operates while the hydro massage pump is running. It will not make your bath warmer, so it is not a substitute for adequate house hot water capacity. Air massage tubs have no heater at all; the blower simply moves air. See how the in-line water heater maintains temperature for the full explanation, and will I get cold while the tub fills or drains for how the heated seat helps at both ends of the bath.

Common Questions

Still need help? Our team is always happy to assist. Open a ticket at ellasbubbles.com/support or call (800) 480-6850.