This should ideally be above the engine level where the head of fuel will provide a positive pressure throughout the fuel system. Any leaks will then result in fuel seeping out rather than air being drawn in. If the tank is alongside or lower than the engine, and a leak develops, air can be drawn into the system when the engine is stopped. A small header tank will provide a positive pressure, but must be vented to the outside to allow flow into the engine fuel system.
Tanks can be made of various materials:
1. Stainless steel – of welded construction, strong and corrosion resistant.
2. Mild steel – of welded construction, coated inside and out with a suitable paint system, to protect against corrosion.
3. Plastic – normally manufactured from polythene and translucent so that the fuel level can
be seen. There is less risk of condensation and no risk of rust forming.
4. Heavy-duty flexible tanks – ideal as temporary tanks for a long voyage or for use in irregular spaces.