Does the in-line water heater warm up my bath? No. The in-line water heater on Ella hydro massage tubs is designed to maintain your bath temperature, not to raise it. You fill the tub with comfortably hot water from the faucet, and then, whenever the hydro massage pump is running, the in-line heater keeps that water at a consistent, comfortable temperature so you stay warm through your whole soak. It will not warm up a bath that was filled with cool water, and it only operates while the hydro pump is on.
How It Works

As the video explains: when you fill your Ella walk-in tub with the five piece or two piece fast-fill faucet set, you set the temperature at the level that suits you best. When you engage the hydro massage, the in-line water heater works together with the water pump to maintain a consistent warm temperature so you stay warm and comfortable. In practice that means: Watch: Ella's Bubbles: In-line Water Heater Maintains Comfortable Water Temperature with a full transcript.
- Fill the tub from the faucet at your preferred temperature. Your home water heater does the heating.
- Once the water is 2 inches above the highest jets, turn on the hydro massage. Our water level article explains why that level matters.
- The in-line heater switches on and off automatically with the hydro pump. There is no separate heater button and no thermostat to set.
- While the hydro massage runs, the heater offsets the natural cooling of the bath and holds the temperature steady.
On tubs equipped with the independent foot massage, the in-line heater is attached to the foot massage pump, so running the foot jets is what keeps the water warm on those configurations. For safety, bath water should be kept at or below 100.4 F.
What the In-Line Heater Is Not
- It is not a water heater for filling. Your household water heater supplies the hot water for the bath. We recommend the largest capacity unit available for your home, and anything under 75 gallons is not recommended. For tankless systems, choose a flow rate of 11 GPM or higher. See what size water heater you need.
- It is not a heater for the air massage. The air system does not have its own heater. Only the hydro loop is heated.
- It is not the heated seat and backrest. That optional system warms the seat surfaces with its own button and has nothing to do with the water.
- It does not run during a still soak. If all pumps are off, the heater is off too. Keeping the hydro massage running is what keeps the heater working.
Which Packages Include It
The in-line heater is included with every hydro massage package. Soaking tubs have no pumps and no heater, and air-only configurations have no heater either, because the air blower simply moves air. Our therapy package inclusions cheat sheet lists what comes with each package.
In-Line Heater Ratings by Model
Every rating below is exactly as printed on the current spec sheets:
| Model | Heater rating |
|---|---|
| Standard, Standard60, Zen, Zen60, Flow | 6A, 650W |
| Elite, Petite, Companion, Escape | 5.5A, 650W |
| Ultra | 5.5A |
| Royal, Deluxe, Front Entry, Shak | 6A, 650W |
| Capri, Lounger, Tub4Two, Big4Two | 6A, 800W |
| Big4One | 6A, 750W |
| Ultimate (heater in the foot and calf hydro loop) | 9A, 1000W |
If Your Bath Still Cools Off Quickly
The most common reason a bath does not stay warm is that it did not start warm enough, usually because the home's water heater ran low while filling. Checking your hot water supply is the best first step. This video walks through how to size your hot water capacity:

Chapters in this video
- 0:00 Hot Water Heater Capacity The video explains the recommended hot water heater capacity for an optimal walk-in tub bathing experience.
- 0:37 Finding Tub Water Capacity The video shows how to find the water capacity of Ella's Bubbles walk-in tubs on the website.
- 1:04 Dedicated Hot Water Supply The video suggests considering a dedicated hot water supply system for your walk-in tub.
- 1:16 Supply Lines And Faucet Sets The video recommends 3/4 inch supply lines and mentions included supply lines with Ella's Fast Fill faucet sets.
As it recommends, check the water capacity of your tub on the Compare Specs page, shown in gallons occupied and unoccupied, and make sure your hot water system can cover the tub plus the other demands in your home. Three quarter inch supply lines with easily accessible shut off valves are recommended, and a dedicated hot water system just for the tub is worth considering for larger models. Your plumber or installer can confirm the right setup for your home. Watch: Ella's Bubbles: Determining Correct Hot Water Supply For A Walk-In Tub with chapters and a full transcript.
If the tub was filled hot and the water still cools quickly with the hydro jets running, or the jets blow noticeably cold water, the heater circuit deserves a look. Open a ticket with your model and serial number so the team can check it; the heater is a replaceable part, and our pump and massage system troubleshooting guide covers the power and connection checks that come first.

Chapters in this video
- 0:00 Why the Customer Chose a Walk-In Tub The interviewer asks the customer what led her to decide on installing an Ella's Bubbles walk-in tub in her home.
- 0:47 Safety and Comfort Features The customer discusses the safety aspects of the tub, including the easy entry and comfortable seat, and mentions the therapeutic lights.
- 1:21 Favorite Features and Temperature Control The customer shares her favorite features, highlighting the consistent water temperature maintained by the tub's inline heater.
- 2:18 Medical Benefits of Hydro Massage The interviewer explains the medical advantages of the hydro massage and air jets, noting their ability to stimulate the immune system.
In this testimonial, a dealer interviews a 93 year old owner who mentions that the in-line heater keeps the water temperature constant during her hydro massage, which is exactly the job it is built for. Watch: Benefits of a Bathroom Walk-In Tub with Door & Seat: Client Testimonial with chapters and a full transcript.
Related Guides
- Hydro Massage vs Air Massage vs Microbubble: What Each System Does and How They Combine
- How to Narrow Down an Ella Walk-In Tub by Space, Door Side and Therapy
- Does My Ella Tub Include an In-Line Heater? Hydro, Air-Only, Soaker and Clearance Units
- Does a Soaking Walk-In Tub Need Electrical Wiring or Keep the Water Warm?
- What are the disadvantages and common problems with walk-in tubs?
- Which Ella walk-in tubs offer quick fill, auto heat and programmable cycles?
If your air massage blows cool air, that is normal because the air pump has no heating element and draws its air from the space under the tub. See why the air massage blows cold air and there is no heating element for what to expect and how to reduce the cold-air feeling.
Common Questions
The water turns cold halfway through filling. Is the heater broken?
Is there a heater button or thermostat?
Will it bring the bath up to 104 F?
How much power does the heater draw?
Is the in-line heater included with all therapy packages?
Does the air massage tub have a heater?
What temperature should my home water heater be set to?
The faucet itself will not give me hot water. Is that the in-line heater?
My in-line heater is leaking. Can it be replaced?
Can heat be added to a tub that does not have it?
Can I leave the heater off my order to keep things simpler?
My new in line heater has a different plug than the one on my old tub. Is that right?
Still need help? Open a ticket at ellasbubbles.com/support or call (800) 480-6850 and our team will be glad to walk through it with you.