YSC Blog Post

Fuel tank sight gauges

27 February, 2017

Sight glasses in tanks to measure the fuel level are wonderfully simple and clear and do not need electrics which is always a bonus on boats. However they are often poorly installed making them a safety hazard.

A poor installation often consists of a length of nylon pipe or PVC hose coupled directly to the tank top and bottom as shown in the picture at the top.

Normally the pipe is not fuel grade and will become cloudy as the fuel degrades it. If the tube is damaged and broken by a knock from loose objects in the locker it will empty your tank and leave you with a dead engine. In the worse case scenario, a fire melts the tube and continues to feed the fire with the contents of your tank and there is nothing you can do to stop it. In the tank on above, that’s 157litres of fuel in the bilges.

To correctly install a sight glass it should be fitted with a self closing valve at the bottom and top so that in the event of the tube breaking - or melting - the fuel will not empty from the tank. The self closing valve in the bottom picture was reasonable cost from Aquafax and simple to install. The sight glass is protected by a metal cover and still clear after 3 years in use.

Just remember push the button each time you need to check the fuel level as it will continue to indicate the last reading.