If your hot water runs out before the tub is full, the house water heater is undersized for the bath you are drawing, and that is the first thing to check. 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. Ella's Bubbles recommends a 75 gallon or larger tank, or a tankless unit rated around 11 gallons per minute. A 40 gallon tank can work only if nothing else draws hot water at the same time. One thing the in line heater 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.

Likely Causes

• A 40 or 50 gallon tank feeding a tub that needs 55 to 75 gallons of hot water per bath.
• A tankless heater rated for a few gallons per minute. A 27 kW unit at 4.8 GPM struggles to keep up with an Ella fast fill faucet.
• Another fixture or appliance drawing hot water during the fill.
• Expecting the in line heater to warm the water.

What to Check, in Order

1. Find your tub's occupied capacity, which is what you actually fill. See water capacity by model. On a Transfer60 that is 55 to 75 gallons depending on the bather; the Big4One holds 127 gallons unoccupied and 75 to 100 occupied.
2. Compare it with your tank. If the tank is smaller than the occupied capacity, hot water runs out about halfway through, which is exactly the symptom owners describe.
3. Fill when nothing else is running. Laundry, a dishwasher or a shower elsewhere shares the same tank. If the tub fills fine alone, the fix is scheduling or a bigger heater.
4. Size the replacement. Staff recommend a 75 gallon tank or a tankless unit around 11 GPM, and the largest tubs may call for a dedicated heater in addition to the one serving the house. See what size water heater do I need.
5. Fill hot from the faucet, then run the hydro massage to hold the temperature. What the in line heater does and does not do explains it.

The video recommends the maximum capacity water heater available for your home, notes that under 75 gallons is not recommended, and shows where the Compare Specs page on ellasbubbles.com lists each tub's capacity in gallons occupied and unoccupied. Whether you will feel cold during the fill is answered in will I get cold while the tub fills or drains.

When to Open a Ticket

If you want the capacity figure for your exact model before choosing a heater, open a ticket at ellasbubbles.com/support with your model or serial number, your current heater size and type, and roughly how far the tub fills before the water turns cold. Your Ella dealer or the team at (800) 480-6850 can confirm the occupied capacity and the heater guidance for your tub.

Common Questions