Every cistern owner knows the ritual: lift the lid, flashlight on, peer in, guess. In July, when no rain falls for weeks and the garden is thirsty anyway, the ritual becomes a daily walk — and the guess is still happily off by a thousand liters. Yet you can measure the cistern’s fill level without ever lifting the lid again: with a battery-powered LoRaWAN sensor that reports the water level to your phone every few minutes — for years, maintenance-free, with no power socket anywhere near the shaft.
This how-to walks you through it step by step: which sensor type fits which cistern, and where the little traps hide that forum threads like to skip.
Wireless cistern level indicator: why LoRaWAN is the right technology
A cistern is hostile territory for radio: underground, behind a concrete lid, often twenty or fifty meters from the house. WiFi usually gives up at the patio door, and running a cable through the garden means digging a trench. This is exactly where LoRa shines — 868 MHz radio penetrates shaft covers and soil surprisingly well and then carries for hundreds of meters to kilometers. And because a LoRaWAN sensor transmits only a tiny packet every few minutes and sleeps in between, its battery lasts five to ten years. For comparison: a WiFi sensor in the same spot would be flat within weeks.
A LoRaWAN gateway in the house receives the data and hands it to platforms like The Things Network, ChirpStack or Home Assistant — where it becomes charts, fill percentages and alerts, however you like it.
Ultrasonic level sensor or pressure probe for the cistern?
| Principle | How it works | Strengths |
|---|---|---|
| Ultrasonic (e.g. Dragino DDS75-LB) | measures contactlessly from above onto the water surface | no calibration, no water contact, simple mounting under the lid |
| Pressure probe (e.g. Dragino LDDS series) | rests on the bottom and measures water pressure | precise even in deep, narrow shafts and with foam |
For the classic garden cistern, ultrasonic is the most convenient choice: the sensor hangs dry under the lid, never touches the water, and measures the distance to the surface — cistern depth minus distance equals fill level. One detail decides between success and frustration here: the dead zone. By principle, ultrasonic cannot measure the first ~25 centimeters below the sensor. Mount it too low, or let the cistern fill to the brim, and it reports nonsense. So: mount the sensor as high as possible and account for the dead zone in your calculation.
The pressure probe earns its keep when things get narrow, deep or turbulent: in slim well pipes, very deep shafts, or when the surface foams and sloshes, pressure at the bottom measures more reliably than any echo from above. In return it lives permanently in the water — uncritical for rainwater; for more aggressive media, check the probe material.
Measuring cistern water level: step-by-step guide
Step 1 — pick a sensor: ultrasonic for standard cisterns, pressure probe for deep or narrow shafts. Both types live in our fill level sensors category.
Step 2 — install a gateway: an indoor gateway in the house easily covers the typical 10–200 meters to the cistern. If yours is farther out or a mound sits in between, our article on LoRaWAN signal strength helps you judge it. Bonus: the same gateway will later serve temperature sensors, a weather station and door contacts.
Step 3 — mount the sensor: screw the ultrasonic sensor centrally under the lid — centrally, because echoes off the shaft wall otherwise produce ghost readings. Lower the pressure probe to the cistern floor and fix the cable at the rim.
Step 4 — connect and visualize: register the sensor via QR code (OTAA) on your network server, enter the cistern dimensions, done. Home Assistant turns it into a percentage gauge with history; an automation warns you at low level before the garden pump runs dry.
What does a wireless cistern level indicator cost?
The sensor runs €60–120 depending on type, an indoor gateway from about €100 — one-off, no recurring fees, because LoRaWAN uses license-free spectrum and the platforms are free. If The Things Network coverage already exists in your neighborhood, the sensor alone is enough. What you get back: no more guessing, timely warnings before the cistern runs empty (and the pump runs dry — pumps famously die of that), plus a quiet data treasure showing how much rainwater your roof actually harvests.
FAQ
Does LoRa really transmit through a concrete lid?
In the vast majority of cases, yes — 868 MHz penetrates concrete surprisingly well, and the distance to the house is usually short. For very deep shafts or heavily reinforced concrete there’s a trick: route the sensor’s antenna on a pigtail cable up just under the lid rim or into the shaft collar. A five-minute test before final mounting settles it for good.
How often does the level sensor measure — and how long does the battery last?
The interval is freely configurable; 15–60 minutes is typical and entirely sufficient, since a cistern changes level slowly. At those intervals the battery lasts five to ten years. Measuring every minute quickly halves the lifetime without adding any information you could act on.
Does this also work for heating-oil tanks, IBC containers or slurry?
Yes — the same technique monitors tanks, silos and vessels of every kind. For heating oil and chemicals there are probes in resistant materials; for bulk solids in silos, radar beats ultrasonic (dust!). The principle — sensor, gateway, dashboard — stays identical, and after the cistern project you already own the gateway.
All matching sensors with German stock are in our fill level sensors category — and if you’re torn between ultrasonic and pressure probe, send us your cistern’s dimensions and we’ll help you choose.