The part number 15ILS (often listed as 1.5ILS) refers to a 1.5kW, 120V in-line electric spa heater manufactured by the Coates Heater Company.
Unlike typical bath heaters, this unit is designed for residential spas and hot tubs with a capacity of less than 400 gallons.
Because the 15ILS is a compact, "universal" in-line heater, it is frequently used as an aftermarket replacement or auxiliary heater rather than just an OEM part.
The following brands and systems are compatible with or have utilized this component:
Sundance Spas: The heater assembly is often used in Sundance systems.
Jacuzzi: It is a common cross-referenced replacement for specific Jacuzzi bath and small spa heaters.
Strong Spas: Specific models, particularly those using certain Balboa or spa packs, are compatible with 15-inch in-line heaters of this type.
Pinnacle Spas: Compatible with universal spa packs that utilize the 15ILS configuration.
Spa Builders (Balboa): Frequently used in systems configured with "Spa Builders" or "PCU" universal spa packs.
Intex & Bestway: Though not an OEM part for these brands, the 15ILS is a very popular "hot tub hack" for owners of inflatable spas (like PureSpa or Saluspa) looking to upgrade their heating speed.
Key Specifications for Identification
If you are verifying this part for your system, check for these physical traits:
Power: 1.5kW (1500 Watts) at 120 Volts.
Dimensions: Usually 15 inches in length with 2-inch or 1.5-inch plumbing connections.
Housing: Stainless steel tank with a built-in pressure switch to prevent dry firing.
Activation: Pressure-activated (it only heats when the pump is running).
Pro Tip: The 15ILS is designed for hard-wiring and typically does not come with a standard 3-prong plug unless it has been modified with a retrofit kit.
