How many gallons of water does a walk-in tub hold?

An Ella walk-in tub holds between 65 and 145 gallons of water with nobody in it, depending on the model, and you use far less than that for a bath because the tub fills after you are seated and your body displaces part of the water. Most standard-size Ella models hold 65 to 107 gallons unoccupied and use 30 to 75 gallons once a bather is seated, while the largest tubs hold up to 145 gallons. How much water does a walk-in tub actually use per bath? goes deep on the occupied figure; this page answers the plain question of how many gallons each tub holds and what that number means for your water heater, your fill and your drain.

Why the Gallon Question Has Two Answers

Every Ella spec sheet prints water capacity as two numbers. The unoccupied capacity is what the tub holds when it is filled with no one inside, and it is the figure most people want when they ask how many gallons a walk-in tub holds. The occupied capacity is printed as a range and tells you how much water you actually draw once you are seated. Because you sit down before the tub fills, the water rises around your body and fewer gallons are needed to reach the same depth. A smaller bather typically lands near the top of the range and a larger bather near the bottom, which is why the occupied figure is never a single number.

Three reading rules keep the figures straight:

• Quote gallons only. 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 at (800) 480-6850 rather than relying on older figures.
• When you are sizing a water heater or estimating a fill, use the occupied figure, because that is the water you will actually heat and pour.

How Many Gallons Each Ella Walk-In Tub Holds

The spread shows where the water goes. 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, so a compact tub is also the lightest load on a water heater. The Elite adds 10 gallons of unoccupied capacity and only a few gallons per bath. The Transfer60 is where the numbers start to outrun a small tank, because its 55 to 75 gallon occupied range is exactly what staff cite when hot water runs out halfway through a fill. The Big4One holds 127 gallons empty yet uses 75 to 100 gallons with a bather in it, and the ShaK and Escape share the 145 gallon top figure, with the two-seat Escape drawing the most water per bath. The Big4Two also holds up to 145 gallons unoccupied. If your real question is which tub your water heater can keep up with, read the occupied column, not the first one.

What the Gallons Mean for Your Water Heater

The capacity figure matters most on the hot side. Depending on the model, a walk-in tub takes roughly 55 to 75 gallons or more to fill once you are seated, and a 40 gallon tank simply does not hold that much hot water. The general guidance from the team is that the average walk-in tub calls for a 75 gallon or larger water heater, with the recommendation being the maximum capacity heater available for your house, or a tankless unit rated at 11 gallons per minute or more. The largest tubs, such as the ShaK and Big4Two, may require a dedicated additional heater. A 40 gallon tank can work only if nothing else draws hot water at the same time, so laundry, a dishwasher or a shower elsewhere during the fill will shorten the hot water noticeably.

One thing the in-line heater on a hydro massage tub does not do is rescue a cold fill. It maintains bath temperature while the hydro jets run and never raises the temperature of water that arrived cool. If the tub is only half full when the water turns cold, the tank is undersized for the occupied capacity, and Why Does My Hot Water Run Out Before the Tub Is Full? walks through the checks in order.

How the Gallons Turn into Fill and Drain Time

The Ella faucet is capable of a fill rate of about 16 gallons per minute, and at that rate a tub with a capacity of around 60 gallons fills quickly rather than leaving you waiting before you can begin bathing. The real-world rate in your home depends on house water pressure, pipe size, the distance from the water heater to the tub, and whether hot water is being used elsewhere at the same time, which is why three quarter inch supply lines with accessible shut-off valves are recommended. How long does it take to fill a walk-in tub? puts the gallons and the flow together.

Emptying is quicker than filling. Ella tubs drain by gravity rather than by pump, and once connected to a proper 2-inch drain line they typically empty in two minutes or less, as Drainage and Fill Time explains. Two models sit outside the faucet rule. The HomeCare Transfer Bathtub carries an 80 gallon internal tank that pre-heats water while the bather is being prepared, so it fills in about 90 seconds after the bather is seated, drains in about 150 seconds, and refills its tank in about 11 minutes for the next bath; it is built for caregiver-supervised bathing only. The LayDown60 is never sold with a factory faucet, so its fill rate depends on the customer-supplied faucet your plumber installs.

The Largest Capacities and What They Ask of a Bathroom

The ShaK leads every published figure: 36 inches by 72 inches, an extra-wide 28 inch seat and a 145 gallon unoccupied capacity, which is why Ella describes it as the largest single-seat walk-in tub in the world. The Big4One, at 33 1/8 inches by 66 inches with a 24 inch seat, is 6 inches shorter and holds 18 fewer gallons unoccupied, so it suits a room that cannot take 72 inches. The two-seat Escape and Big4Two match the ShaK on capacity and add a second seat to rest your feet on. What is the biggest walk-in bathtub size you can buy? compares them side by side. The practical point is that more gallons means more hot water to make and more time at the faucet, so a tub at the top of the table should be paired with the heater sizing above before installation day. Your Ella dealer or the team at (800) 480-6850 can confirm the figures for the model you are considering.

Related Guides

• What Size Water Heater Do I Need for My Walk-in Tub?
• How to Read an Ella Spec Sheet: Actual Versus Nominal Size, Shipping Size, Occupied Versus Unoccupied Capacity, Package Jet Tables, Amp Disclaimers and Known Misprints
• How many gallons does each Ella walk-in tub hold? Water capacity guide

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