What Temperature Does the In-Line Heater Hold, and Can I Adjust It?

The in-line heater on an Ella walk-in tub does not hold a fixed, factory-set temperature. It maintains whatever temperature you filled the tub with, and it runs only while the hydro pump is running, so there is no heater thermostat, dial or button to adjust. You set your bath temperature at the faucet as the tub fills, and the heater then offsets the natural cooling of the water during your hydro massage, as explained in What Is an In-Line Water Heater on a Walk-In Tub?.

There Is No Set Point to Change

Owners sometimes look for a temperature display or a heater control on the deck and wonder whether something is missing. Nothing is missing. The in-line heater is plumbed into the hydro massage loop under the tub. When you switch on the hydro massage, the pump pulls water through the heater and back out through the jets, and the heater adds just enough warmth to hold the bath steady against the cooler air in the room. It switches on and off with the pump. It has no thermostat you can set, no separate heater button and no display, because its job is to keep the water at the temperature you chose rather than to bring the water to a temperature of its own.

That design has three practical consequences worth knowing before your first bath:

• The temperature it holds is the temperature of your fill. A hot fill stays hot for the length of the hydro massage, and a lukewarm fill stays lukewarm.
• It never raises the temperature. It cannot rescue a bath that arrived cool from the house water heater, no matter how long the jets run.
• It does nothing while the hydro pump is off. If you soak with the jets switched off, the water cools the way any bath does.

The short company video on this page shows the routine in one breath: you set the temperature at the fast-fill faucet to the level that suits you best, and when you engage the hydro massage, the in-line heater working with the water pump maintains a consistent warm temperature so you stay comfortable.

How You Actually Adjust Your Bath Temperature

Because the heater follows the fill, the faucet is your temperature control. The sequence below is the one Ella describes for its hydro tubs.

1. Step in, close and lock the door, close the drains and turn on the water. On the five-piece fast-fill faucet, hot is on the left, cold is on the right and the shower selector sits in the middle. Adjust the mix until the water feels comfortable, taking care not to scald yourself.
2. Fill until the water is 2 inches above the highest jets. The hydro pump should not be started before the jets are covered.
3. Switch on the hydro massage. The pump starts, the heater comes on with it, and the bath holds the temperature you set.
4. If the water feels too warm or too cool once you are seated, adjust it at the faucet by adding a little hot or cold water. There is nothing to adjust at the heater.

Tubs ordered with an Ella thermostatic faucet package include a built-in thermostatic control valve that mixes hot and cold water to a set temperature. That valve is the closest thing an Ella tub has to a temperature setting, and it belongs to the faucet, not to the in-line heater. It carries its own 1-year limited warranty, separate from the lifetime limited parts warranty that covers the heater and pump as supporting equipment.

Ella's guidance is to keep bath water at or below 100.4 degrees Fahrenheit. Whatever comfortable temperature you choose within that guidance is the temperature the heater will hold for you.

What Decides Your Bath Temperature Before the Heater Ever Runs

Since the heater only maintains, the temperature of your bath is decided by your home water heater, and that is where most questions about the tub not staying warm really begin. Depending on the model, a walk-in tub takes roughly 55 to 75 gallons or more to fill once you are seated. A 40 gallon tank simply does not hold that much hot water, and when the hot runs out partway through the fill, the bath finishes cooler than you wanted. The in-line heater then faithfully holds that cooler temperature, which is exactly the symptom owners describe.

Ella's Bubbles recommends the maximum capacity water heater available for your house, and anything less than 75 gallons is not recommended. If you prefer tankless, the recommendation is a unit rated around 11 gallons per minute. 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 in the home should wait until the tub is full. 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. Use 3/4 inch supply lines with easily accessible shutoff valves, and note that Ella's 2-piece and 5-piece fast-fill faucet sets include 5 foot supply lines. The sizing guidance is laid out in Why Does My Hot Water Run Out Before the Tub Is Full?, and the division of labor between the two heaters is the subject of Do Walk-In Tubs Have Heaters to Keep the Water Warm?. Every home is different, so consult your installer or a professional plumber before choosing a heater.

Which Heater Is on Your Tub, and Where It Sits

Every Ella tub with a hydro massage package has an in-line heater, across the Standard and Zen family, the stainless-door tubs, the Ultra, the outward-swing tubs, the two-seat tubs, the Transfer tubs and the LayDown hydro option. The spec sheets list the heater by its electrical rating rather than by a temperature, because it has no temperature of its own to list:

• 6A 650W on the Standard, Zen and Flow.
• 5.5A 650W on the Elite and Petite.
• 9A 1000W on the Ultimate foot loop.

Those figures describe how much power the heater draws while it runs, and your electrician uses them when sizing the dedicated GFCI protected circuit. Like the pumps and other electrical components inside the tub, the heater is ETL certified and clearly marked, and it sits where an electrician can reach it during installation.

One configuration detail changes how you operate the tub. On tubs with Hydro plus Independent Foot Massage, such as the Ultimate, the heater is attached to the foot massage pump rather than the seat pump. On those builds, running the foot massage is what keeps the water warm, so if you run only the seat and back jets the heater is not in the loop. The air massage has no heater at all, and air-only and soaking tubs have no hydro pump and no heater, so a heater cannot be added to those configurations later.

When the Water Still Will Not Stay Warm

If you filled hot and the water still drops noticeably during a hydro session, work through these checks before assuming the heater has failed. Confirm that the hydro massage is actually running, since the heater has no switch of its own and only comes on with the pump. Confirm that your tub has a hydro package rather than an air-only or soaker configuration. On a Hydro plus Hydro Foot tub, run the foot massage, because the heater is powered with the foot pump. Then check the heater cord at the control box under the tub, because a heater plugged into the wrong port never runs, and if the heater and lights stopped working together, check the green LED on the box and the GFCI as well. Cold bathroom air and a poorly insulated room also work against the heater. The full sequence, with what to photograph, is in Why Doesn't the Water Stay Hot and Why Do the Jets Blow Cold?.

For comfort before and after the hydro massage, the tub relies on other features rather than the heater. The glossy acrylic shell acts as an insulator, the fast-fill faucets shorten the wait, and the optional heated seat and backrest warms the seat before you sit down and switches itself off after 20 minutes, with a push of the button turning it back on. At the end of the bath, the dual 2 inch drains empty an average tub in approximately 80 seconds under ideal conditions. Those points are covered on video in Will I Get Cold While the Tub Fills or Drains?.

If the checks above do not explain the cooling, open a ticket at ellasbubbles.com/support or call your Ella dealer or the team at (800) 480-6850. Have your model, serial number, therapy package and a photo of the control box with every cord visible, so the team can confirm the heater connection and, if a part is needed, ship it under the warranty for your local licensed plumber or electrician to fit.

Watch: Ella's Bubbles: In-line Water Heater Maintains Comfortable Water Temperature with chapters and a full transcript.

Related Guides

• Does the in-line water heater warm up my bath? What it does and does not do
• What Size Water Heater Do I Need for My Walk-in Tub?

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