How much water does a walk-in tub actually use per bath?

Most standard-size Ella walk-in tubs use 30 to 75 gallons of water per bath once you are seated, even though the same tubs hold 65 to 107 gallons with nobody in them. The figure you actually use is the smaller occupied number, because an Ella walk-in tub fills after you are seated and your body displaces part of the water. Every model's pair of figures is listed in How many gallons does each Ella walk-in tub hold? Water capacity guide.

Why Every Tub Has Two Gallon Figures

Ella spec sheets print water capacity as two numbers. Unoccupied capacity is how many gallons the tub holds with nobody in it. Occupied capacity, written as a range, is the amount of water you use once a bather is seated and displacing water. Your body takes up space, so the water level rises around you and fewer gallons are needed to reach the same depth. That is also why the occupied figure is a range rather than a single number: the actual volume varies with bather size, so a smaller bather typically uses the upper end of the range and a larger bather the lower end. What Is Occupied vs Unoccupied Water Capacity on a Walk-In Tub? walks through the idea with examples from the current sheets.

Three things to keep in mind when reading a sheet. Use gallons only, because the litre conversions printed on some sheets, including the Big4One sheet, are misprints. The Monaco, Mobile and LayDown60 capacities are not printed on the current spec sheets, so check the live product page or ask the team rather than relying on older figures. And when you are estimating a fill, the occupied figure is the better guide, since fill time is capacity divided by the real-world flow at your faucet.

Water Used per Bath by Model

The spread tells you where water use really comes from. The Petite, Standard, Zen and Flow all hold 65 gallons unoccupied and use 30 to 50 gallons per bath, the lowest figures in the line, while the ShaK, Escape and Big4Two hold up to 145 gallons unoccupied. A bigger tub holds more water because it has more interior to fill, and a two-seat tub uses more because it is sized for two bodies. If water use is your concern, compare occupied ranges, not the unoccupied headline, and remember that a larger bather in a given tub uses less water than a smaller one.

The Occupied Figure Sizes Your Hot Water

The reason the occupied number matters most is hot water. A fast faucet only helps if the water stays warm for the whole fill, and a house water heater smaller than the occupied capacity runs out about halfway through, which is exactly the symptom owners describe. The general guidance from the team is that the average walk-in tub usually calls for a 75 gallon or larger water heater, and the recommendation is the maximum capacity heater available for your house. A tankless heater should be rated at 11 gallons per minute or more; a 27 kW unit at 4.8 gallons per minute struggles to keep up with an Ella fast-fill faucet. A 40 gallon tank can work only if nothing else draws hot water at the same time, since laundry, a dishwasher or a shower elsewhere shares the same tank. The largest tubs, such as the ShaK and Big4Two, may require a dedicated additional heater. One thing the in-line heater on hydro massage tubs does not do is rescue a cold fill: it maintains bath temperature while the pump runs and never raises the temperature of water that arrived cool, so your house heater does all the work of filling the tub hot. Why Does My Hot Water Run Out Before the Tub Is Full? lists the checks in order.

How Fast the Water Goes in and Out

The Ella faucet is capable of a fill rate of about 16 gallons per minute, so a tub with a capacity of around 60 gallons fills quickly rather than leaving you waiting before you can begin bathing. Real-world flow depends on house water pressure, pipe size, the distance from the water heater to the tub, and hot water being used elsewhere at the same time, which is why How long does it take to fill a walk-in tub? treats the occupied gallons and your plumbing as the two numbers that set the wait. Draining is quicker still. Every Ella tub uses two 2 inch gravity-driven drains rather than a pump, and when the tub is connected to a proper 2 inch drain line it typically empties in two minutes or less, as Drainage and Fill Time explains. Three quarter inch supply lines with accessible shut-off valves are recommended, and both Ella fast-fill faucet sets include two 5 foot braided supply lines.

Two Models That Work Differently

• HomeCare Transfer Bathtub. It holds 78 gallons unoccupied and 35 to 55 gallons occupied, but it fills from an 80 gallon internal tank that pre-heats water while the bather is being prepared. The tub fills in about 90 seconds after the bather is seated, drains in about 150 seconds, and the tank refills in about 11 minutes for the next bath. It is built for caregiver-supervised bathing only.
• LayDown60. It is never sold with a factory faucet, so its fill rate depends on the customer-supplied faucet your plumber installs, and its capacity is not printed on the current spec sheet.

What to Have Ready Before You Ask

If the tub fills slower than you expected or the water goes cold, compare the occupied figure for your model with your faucet's real flow before assuming a fault. When you open a ticket at ellasbubbles.com/support or call (800) 480-6850, have your model name, your water heater size and type, your supply line size, and a timed fill on hand. Your contractor should assess pressure, pipe runs and heater capacity with the occupied figure in hand before installation day.

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