This device uses water as a piston and simple ball valves to pump air.

A tubular container is organised like a tall inverted cup. Its open end is attached to a weighted drag disc by a long string. It upper end has a flotation collar attached to it.

When a wave rises, the pump body is prevented from rising as fast as the wave by the drag disc. Because the pump body is below the wave level, water is forced into the open lower end of the container. Air above the water is pushed through a water trap that lets air through but not water. A valve into an outlet pipe prevents the air from going back into the pump. .When a wave falls, the pump falls less quickly and the water level in the pump body falls, causing a reduction of air pressure inside the pump body. This sucks air in through an inlet pipe that is fitted with a splash guard.

The inside of the pump is divided into upper and lower chambers. A float and ball valve arrangement prevents water rising into the upper chamber of the pump. Any water sucked in through the air inlet can drain down into the lower part of the pump.

The outlet from the pump may be connected to anything that can be inflated by low pressure air.

The typical pressure that the pump can deliver is between 6 and 12 inches of water. This is more than enough to inflate most water borne inflatables.

The drawing of the pump shows the general principles. It is not drawn to scale. A working model would be three or four times as tall in relation the the width shown in the drawing.

Copyright (C) W. H. James 14/6/1998
Wilf James,106 Jarden, Letchworth, Herts. SG6 2NZ, UK.
E-mail wilf.james@ntlworld.com