What Size Water Storage Heater Do I Need?

What Size Water Storage Heater Do I Need?

Most boat owners choose to store as much hot water as they can in the space available.

10-15 litres of water at 50 deg C is sufficient for a refreshing hot shower. With limited fresh water supplies on board, less than 10 litres is often enough. A small pressurised water pump will deliver 5 – 10 litres/minute. The water consumption of a shower will depend on shower head design, water pressure and pipe size.

No. of Persons Aboard Heater Capacity Litres (Gall) Length of Vessel m/ft
1-2 14-28 (3-6) 7.5-10 (25-33)
3-4 28-55 (6-12) 10-12.5 (33-40)
5-6 55-70 (12-15) 12.5-15 (40-50)
7-10 95-136 (21-30) 15-18 (50-60)

This table is intended as a rough guide to selection. Besides the space available, personal preference and cost may also influence the choice. No. of persons is defined by the number of people requiring consecutive hot showers at 10 litres per shower.

Space Available

Check the space available, preferably close to the engine. Is there room to locate, support and secure the heater and connect the pipework? Is there room to fit or remove an electric immersion heater if necessary?

The space available will determine the choice of a horizontal or vertical heater. C-Warm heaters come in a range of sizes to suit most requirements.

Vertical tanks are thermally a little more efficient, but a horizontal tank can sometimes make better use of available space.

Case or Uncased?

If the heater is to be installed out of sight, an uncased model will be the more economical choice. If the heater is to be a prominent feature of the galley, saloon, or engine room, a smart painted steel or stainless steel casing will match the appearance of the finest equipment on board. Cased and uncased models are identical in performance.

Single or Twin Coil?

Choose a single coil model unless you plan to utilise waste heat from more than one engine, or install an auxiliary burner to heat the water when the engine is not running.

Immersion Heaters

Immersion heater power is often limited by onboard a.c. generator capacity or by the shore supply. A double-protected immersion heater with twin thermostats and Incoly element sheath is strongly recommended.