Your tank dip is the only physical check on what's really in the ground. Every stock loss figure depends on it, so a careless dip can create a "loss" that never happened, or hide one that did. A consistent routine fixes most dip problems.
Safety first: follow your site's safety procedures and local regulations whenever a tank is opened. No smoking or open flames, use the correct equipment, and keep the area clear.
When to dip
- At the same time every day, so each dip covers the same period of sales.
- When dispensing from that tank has paused, so fuel isn't moving while you measure.
- Before and after every delivery. Wait for the fuel to settle before the "after" dip, typically 15 to 30 minutes, or as your supplier advises. Dipping straight away gives a false, unsteady reading.
A simple dipping routine
- Check the dip stick. It should be clean, dry, straight and the right one for that tank, with clearly readable markings.
- Note the time and the latest meter readings for the nozzles on that tank, so the dip lines up with your sales figures.
- Lower the stick slowly and vertically until it touches the bottom of the tank. Don't let it drop, or fuel will splash up the stick.
- Withdraw it steadily and read the wet line straight away, to the nearest millimetre, before it evaporates.
- Dip twice. If the two readings differ by more than a couple of millimetres, take a third and use the two that agree.
- Check for water by applying water-finding paste to the bottom of the stick on a separate dip. The paste changes colour where water is present.
- Record the depth immediately, along with the water level, date, time and who took it.
Converting depth to litres
Tanks aren't simple boxes, so the same change in depth means different volumes at different levels. That's why each tank needs its own calibration chart (sometimes called a dip chart or strapping table), supplied when the tank was installed or calibrated.
If your reading falls between two rows, work out the volume in proportion. For example:
| Depth (mm) | Volume (litres) |
|---|---|
| 1,500 | 16,820 |
| 1,510 | 16,950 |
| Your reading: 1,504 | 16,872 |
Subtract any water volume from the total to get the fuel volume, because water isn't stock you can sell.
Common dip mistakes
- Dipping during or right after a delivery, before the fuel has settled.
- Reading the wrong chart, especially at sites with tanks of different sizes.
- Rounding to the nearest centimetre. On a large tank, 10 mm can be over 100 litres.
- Different staff, different methods. Train everyone on the same routine.
- Skipping days. A missing dip means two days of variance get lumped together and the cause is harder to find.
What to do with the reading
A dip on its own only tells you what's in the tank. Its real value comes from comparing it with your book stock: opening stock plus deliveries minus litres sold. The difference is your gain or loss for the day. Here's how to calculate it step by step.
Automatic tank gauges can take readings for you, but many stations still rely on manual dips, and even gauged tanks benefit from a regular manual check. In FuelBotics, staff record each dip and the system works out book stock from your readings and deliveries, shows the loss or gain between every dip, and alerts you when a gap is larger than it should be.
