ualified Boat Safety Scheme (BSS) examiner for inland waterway vessel inspections

Gas Safe Registered engineer for marine LPG gas installations and safety certificates

OFTEC certified technician for marine diesel heating and oil-fired appliance servicing



For boaters who require a “domestic-style” heating experience, a hydronic diesel system is the premier choice for on-board climate control. These units, often referred to as “wet heaters,” circulate a heated water-glycol mixture through a circuit of radiators or matrix heaters, while simultaneously providing a consistent supply of domestic hot water via a calorifier. This method of marine climate control is exceptionally quiet and offers superior heat retention compared to air-based systems, making it ideal for larger vessels and year-round live-aboards.

The Specialist Difference: Hydronic System Engineering

Designing a water-based heating circuit requires a high level of technical precision to ensure the system operates without “cycling” or overheating. Our engineering approach focuses on hydraulic balancing and component longevity.

  • Radiator Circuit Balancing: We calculate the specific heat output required for each cabin to ensure the boiler runs at its most efficient temperature.
  • Calorifier Integration: We expertly integrate the heater with your boat’s domestic water system, ensuring you have hot water for showers and galleys without needing to run the main engine.
  • Expansion & Safety: Professional installations include correctly sized expansion tanks and over-pressure valves to protect the integrity of your plumbing under varying thermal loads.


Premium Diesel Water Heater Brands

We provide professional installation and commissioning for the industry’s most reliable hydronic manufacturers:

Webasto Boat Air and Liquid Diesel Heaters

Webasto: The Thermo Pro 90 and Thermo Top series are renowned for their quiet operation and compact design.

Autoterm Heaters Logo

Autoterm: The Flow 5 (Hydronic) is a rugged, service-friendly unit that offers exceptional value for high-use vessels.

Eberspacher Heaters Logo

Eberspächer: The Hydronic series offers high-performance German engineering with sophisticated digital control options.

Our Diesel Water Heaters

See all our diesel water heaters in no particular order below. This is a collection of compatible models across our range; for more detailed listings and technical specifications, please follow the main menu to our manufacturer-specific pages.


Safety/Regulatory: OFTEC and Canal & River Trust (CRT)

To ensure your vessel remains compliant with Canal & River Trust (CRT) licensing, all diesel water heaters must be installed according to Boat Safety Scheme (BSS) mandates. This includes specific requirements for the installation of ISO 7840-compliant fuel hoses, fire-protected copper fuel lines, and correctly routed wet exhausts.

As OFTEC registered technicians, we ensure that every hydronic system meets the relevant standards. Our commissioning process includes a full analysis to verify that the heater is burning cleanly, preventing carbon buildup and protecting your manufacturer’s warranty.

A professional Autoterm Flow 5 diesel liquid heater installation in a steel narrowboat engine bay, featuring BSS-compliant 5mm copper fuel lines, a secured fuel filter, and ISO 7840 flexible hose connectors.
Technical view of an Autoterm Flow 5 (Hydronic) installation. The setup highlights the “right first time” engineering approach, including fire-resistant copper fuel lines and professional plumbing for narrowboat central heating.