How to measure your tank level
without opening the tank
Pressure sensor, external ultrasound, mechanical gauge: complete comparison of methods for checking your water tank level without opening it.
Opening a water tank is never trivial: the lid may be heavy, objects may fall in and debris can contaminate the water. A tank is also a confined space that you must never enter. Modern solutions let you check the level without opening the access hatch for every reading.
This article compares the different methods available in 2026: from a conventional mechanical gauge to the connected LoRa sensor and external ultrasonic solutions. You will know everything to make the right choice according to your type of tank and your needs.
Contents
straighten 1. The mechanical gauge (dipstick and float)
The oldest and most common method: graduated stem descends into the tank from the top, with a float that indicates the level on a scale visible to the naked eye. Simple, robust, but which requires access to the top of the tank and opening the lid to read the measurement.
Some recent mechanical gauge models allow remote reading via a cable that goes up to a wall indicator housing. But in any case, the initial installation requires drilling and opening the tank. The accuracy is limited (approximately ±50 to ±100 litres) and there is no warning or history function.
For buried tanks, the mechanical gauge is particularly restrictive because access is often difficult and can be obstructed by vegetation or snow. This is why many owners are looking for more modern alternatives.
graphic_eq 2. The external ultrasonic sensor
The ultrasonic sensor is an interesting option as it does not require contact with the liquid. Placed above the surface, it emits a high frequency sound wave and measures the time it takes for the echo to return. The distance between the sensor and the liquid surface allows the level to be calculated.
Some models can be installed outside the tank, glued to the metal or plastic wall. They then function by ultrasonic transmission through the wall (doppler effect or transit time). This is the most "no contact" method: no opening, no drilling.
However, this technique has limitations. Ultrasonics can be disturbed by foam formed on the surface of the liquid (in particular), by thick walls of buried tanks, or by condensation. The accuracy is less than that of a submerged sensor. And the power consumption is higher, which reduces battery life.
pressure 3. The hydrostatic pressure sensor
The pressure sensor (or hydrostatic sensor) is the most reliable and accurate solution. Placed at the bottom of the tank, it measures the pressure exerted by the column of liquid above it. This pressure is directly proportional to the liquid height, therefore to the remaining volume.
The initial installation requires an opening of the tank to place the sensor at the bottom. But once installed, you never need to open the tank again. The sensor transmits data via wireless LoRa, and the reading is done from your smartphone or computer.
The benefits include ±2-litre accuracy, real-time monitoring and hydrostatic measurement for rainwater tanks and other compatible water reserves. Tankio uses a pressure probe, never an ultrasonic sensor.
table_chart 4. Comparison of methods
| Criteria | Mechanical gauge | External ultrasound | LoRa pressure sensor |
|---|---|---|---|
| Accuracy | ±50 to ±100 L | ±10 to ±30 L | ±2 L |
| Need to open the tank | Yes (at each reading) | No (after installation) | No (after initial installation) |
| View | Local visual | App / Screen | Mobile / web app |
| Alerts | None | Notification (depending on model) | Push, email |
| Battery life | Unlimited (mechanical) | 6-12 months | 3+ years |
| Indicative price | 20-80 € | 80-400 € | See the Tankio offer |
shield 5. Safety: limit opening
Safety is too often overlooked when checking a water tank. Lifting a heavy access cover, leaning over the opening or working in a cramped area can cause falls and contaminate the water. Never enter a tank: it is a confined space.
With a connected sensor, you completely eliminate this risk. Once the sensor has been installed by a professional (or by yourself following the safety instructions), you never need to open the tank again. Reading is done remotely, safely, from your living room.
For rainwater tanks, repeated opening can introduce contaminants (dust, insects, leaves) that degrade water quality. The connected sensor preserves the tank’s sanitary seal while giving you accurate information on the level. Consult our FAQ on the connected gauge for more details on the safe installation.
Good safety practices
- Never enter a tank: it is a confined space.
- Secure the cover before opening and keep children away.
- Use a professional if access is difficult or the installation presents a risk.
- Avoid introducing dust, leaves or tools into the water.
- Regularly check the correct functioning of sensor alerts.
star 6. The solution recommended by tankio
After comparing the available methods, Tankio uses one configuration only: a hydrostatic-pressure probe for water, linked over LoRa to the included gateway, which connects to the internet over WiFi.
Here is why: Once installed (a one-off 15-minute operation), you never open the tank again. The sensor offers an unparalleled accuracy of ±2 liters, a battery life of 3+ years, personalized alerts, and complete historical monitoring. Whether you have a tank or a rainwater tank, the sensor fits your installation.
LoRa technology ensures a long range even through thick walls and concrete slabs. And because the sensor is immersed (in contact with the liquid), it is not disturbed by foam, vapour or condensation, unlike external ultrasonic solutions.
check_circle 7. Choose the right solution
Measuring the level of your tank without opening the tank is not only possible, but it is also safer, more accurate and more convenient. Modern technologies such as the LoRa pressure sensor transform the chore of checking the level into a simple action: a look at your smartphone.