In-Line Water Heater for Jetted Bathtubs

What Is an In-Line Water Heater?

An in-line water heater is designed to maintain the water temperature in your bathtub during use. Unlike hot tubs, it does not heat cold water to bathing temperature, but rather helps keep your bath warm for longer periods.

Will It Heat the Water?

Yes—but gradually. The heater only functions when the water jets are running, and over the course of about 30 minutes, it may raise the water temperature by approximately 3-4 degrees.

Is It Safe?

Absolutely. Most in-line heaters feature a built-in pressure switch, meaning they will only activate when water is flowing through them—preventing overheating or dry operation. This makes them very safe to use in home bathtubs.

How Can I Tell If It’s Working?

While a few heaters have a built-in indicator light, it's often hidden from view during use. The most reliable way to check functionality is to use a water thermometer before and after jet operation.

How Long Will It Last?

Manufacturers typically design in-line heaters to outlast the bathtub itself, requiring little to no maintenance over its lifetime.

Can I Use Bath Salts?

Yes. Using bath salts in a tub with an in-line heater is safe. Bath salts have minimal effect on the heater’s performance or longevity.