Tank gauges and level indicator guide

Whether you have domestic heating oil in a single tank or a tank farm storing millions of litres of oil, it’s important to know how much fuel (or other liquid) you have in stock.  This guide looks at  different types of tank gauges and level indicators, explains how they work and which type might suit your needs.

Sight tubes (sight gauges)

This is a simple clear tube, usually made from PVC; one end connected to the top of the tank and the other to the bottom.   The level of the tank is seen visually in the tube to give an indication of the remaining fuel.  They are usually found on domestic heating oil tanks, but also on older farm, agricultural tanks and some commercial tanks.  Sight tubes are no longer used on new bunded tanks as they can leak, potentially emptying the entire contents of the tank if the tube becomes damaged, falls over or if the valve gets stuck open.  The PVC material also goes cloudy and becomes difficult to read over time.  These simple sight tubes are still used on single skin tanks with tank master outlets and on tanks inside a bund.   Cheap and simple, they can be prone to water and insects getting stuck in the tube.

Float gauges

Float gauges are simple mechanical gauges, reliable and cost-effective.  As the name suggests, a float allows a cable to operate an indicator needle to display the tank contents.  Easily installed on the top of the tank, these allow the float and cable to move with the liquid level.  They’re simple to read, with very little to go wrong.  Most float gauges have a 1 1/2″ bsp thread and read in height, but can be calibrated to read litres.

Watchman Sonic

These types of fuel tank gauge are a little more sophisticated. They use a sonic radar to detect the level of the oil below the gauge. It measures the time it takes for the sound wave it sends out to reflect from the oil.   There are several variants of the Watchman depending on your needs.