Marine Calorifiers – Compact, Reliable Hot Water Storage for Boats
Ideal for:
- Yachts and narrowboats
- Offshore support vessels
- Houseboats and liveaboards
- Commercial marine applications
A Marine Calorifier is a simple and efficient means of storing hot water, making it readily available, whether that’s in the shower, galley, or washbasin. As a result, it ensures a steady supply of hot water while you’re on board.
Our range of hot water boat tanks is designed to supply a constant supply of hot water from multiple heat sources, all within a small form factor. In addition, they are built to withstand the unique challenges of marine environments.
Durable Construction: We use thicker copper as standard. This means they are better equipped to handle high pressure and are built to last. Every bespoke boat unit has excellent pressure resistance and long-term reliability, ideal for demanding marine environments.
Flexible Orientation: Choose between horizontal or vertical designs to suit your available space and layout.
High-Efficiency Coils: Our finned copper coils deliver fast, efficient heat transfer, optimised for both boiler and engine circuits.
Information on our Industrial Calorifiers can be found here.
Need a custom marine calorifier for your boat?
Contact our sales team, and we’ll help you build the right solution.
Specification
| Maximum Working Pressure | 3.0 BAR |
| Test Pressure | 5.0 BAR |
| Max Coil Working Pressure | 3.5 BAR |
| Coil Test Pressure | 7.0 BAR |
| Coil Heating Surface | 0.54m² |
| Material Gauge (*Dependent on cylinder diameter) | 1.2 - 1.8mm* |
| Insulation Thickness (Nominal) | 25mm |
Size Guide
| Imperial Size (Inch) | Metric Size (mm) | Overall Metric Size (mm) | Litres | Gallons |
|---|---|---|---|---|
| 18x12 | 450 x 300 | 500 x 350 | 28 | 6.2 |
| 24x12 | 600 x 300 | 650 x 350 | 38 | 8.4 |
| 30x12 | 765 x 300 | 815 x 350 | 48 | 10.7 |
| 33x12 | 850 x 300 | 900 x 350 | 51 | 11.3 |
| 36x12 | 900 x 300 | 950 x 350 | 58 | 12.9 |
| 18x14 | 450 x 350 | 500 x 400 | 34 | 7.6 |
| 24x14 | 600 x 350 | 650 x 400 | 48 | 10.7 |
| 30x14 | 765 x 350 | 815 x 400 | 62 | 13.8 |
| 33x14 | 850 x 350 | 900 x 400 | 67 | 14.9 |
| 36x14 | 900 x 350 | 950 x 400 | 76 | 16.9 |
| 18x15 | 450 x 375 | 500 x 425 | 38 | 8.4 |
| 24x15 | 600 x 375 | 650 x 425 | 54 | 12.0 |
| 30x15 | 765 x 375 | 815 x 425 | 70 | 15.6 |
| 33x15 | 850 x 375 | 900 x 425 | 75 | 16.7 |
| 36x15 | 900 x 375 | 950 x 425 | 86 | 19.1 |
| 18x16 | 450 x 400 | 500 x 450 | 42 | 9.3 |
| 24x16 | 600 x 400 | 650 x 450 | 60 | 13.3 |
| 30x16 | 765 x 400 | 815 x 450 | 78 | 17.3 |
| 33x16 | 850 x 400 | 900 x 450 | 84 | 18.7 |
| 36x16 | 900 x 400 | 950 x 450 | 97 | 21.6 |
| 18x18 | 450 x 450 | 500 x 500 | 42 | 9.3 |
| 24x18 | 600 x 450 | 650 x 500 | 73 | 16.2 |
| 30x18 | 765 x 450 | 815 x 500 | 97 | 21.6 |
| 33x18 | 850 x 450 | 900 x 500 | 104 | 23.1 |
| 36x18 | 900 x 450 | 950 x 500 | 120 | 26.7 |
| 42x18 | 1050 x 450 | 1100 x 500 | 141 | 31.3 |
FAQs
What is a Calorifier?
A calorifier is a type of hot water storage vessel that heats water indirectly using an external heat source. Unlike a standard hot water cylinder that may use a direct immersion heater, a calorifier relies on a heat exchanger coil through which hot water or steam from a boiler, engine, or other heat source is circulated. The heat transfers through the coil wall into the stored water without the two supplies ever mixing.
Calorifiers are widely used in marine, commercial, and industrial applications where reliable hot water storage is needed from an existing heat source.
What does a calorifier do?
A calorifier heats and stores domestic hot water so it is available on demand at taps, showers, and other outlets. It works by drawing heat from a primary source (such as a boiler, engine cooling system, or heat pump) and transferring it to a separate body of stored water via an internal coil.
This means the water you use for washing and cleaning is heated efficiently without requiring its own dedicated burner or heating element, though many calorifiers also include an immersion heater as a backup or secondary heat source.
How does a calorifier work?
Hot water or steam from the primary heat source is circulated through a coil fitted inside the calorifier.
As the hot fluid passes through the coil, heat transfers through the coil wall and into the surrounding stored water. The primary fluid and the stored domestic water never come into contact with each other, keeping the two circuits completely separate.
Once the stored water reaches the desired temperature, it is available at mains pressure or system pressure, depending on the installation.
When hot water is drawn off, cold water enters the vessel to replace it, and the heating cycle continues as long as the primary heat source is active.
What is a marine calorifier?
A marine calorifier is a hot water storage vessel purpose-built for use on boats and inland waterways.
Like a standard calorifier, it heats water indirectly using a heat exchanger coil, but is designed specifically for marine environments. They are typically more compact to fit within tight engine bays and cabin spaces, and connect to a boat’s engine cooling circuit as a primary heat source, heating your domestic water using waste heat from the engine while underway.
Most marine calorifiers also include an immersion heater for use when connected to shore power, and twin coil options allow both heat sources to work independently or together.
This ensures a steady supply of hot water at the shower, taps, and galley, whether you’re cruising or moored up.
How is water heate in a marine calorifier?
Direct Heating: Uses an internal immersion heater powered by the boat’s electrical system or solar PV to heat the water.
Indirect Heating: Uses a coil inside the calorifier to transfer heat from the boat’s engine or external boiler.
Twin Coils: These allow two heat sources (e.g. engine + boiler) to work in tandem, improving efficiency and reliability.
Installing a marine calorifier
Installing a calorifier unit is relatively straightforward if your boat has a pressurised water system and space near the engine. It can be heated via the engine or shore power immersion heater. Read more here
Example Diagram
