Installing the water level sensor

Updated 9 October 2026Fluidy

For each tank you need a level sensor (available separately in the shop), a hole with a diameter of 17mm and the supplied watertight cable gland (M20, protection class IP68). The sensor hangs in the tank and measures how strongly the water presses on it. From this it works out how full the tank is. Installation is the same for fresh, grey and black water tanks.

Step by step

  1. Choose the drilling point: the 17mm hole goes in the top or side of the tank, close to an inspection opening your hand fits through. We recommend a step drill. But stop in time, otherwise the hole gets too big and the cable gland no longer seals.
  2. Fit the cable gland: screw the cable gland into the hole and make sure the seals sit correctly.
  3. Insert the sensor: guide the sensor through the inspection opening into the tank and the cable out through the cable gland.
  4. Align the sensor: the sensor must touch the bottom of the tank and hang vertically. Ideally, secure it with cable ties to a strut in the tank. Then it stays straight and does not swing when the tank is empty.
  5. Seal: tighten the cable gland around the cable.
  6. Connect: cable into the 3-pin connector: blue to pin 2, red to pin 3, pin 1 stays free. Plug the connector into a water level input on Fluidy Pro.
  7. Set up: create the tank in the dashboard under Add widget and then Water tank. The calibration guides you step by step, you do not have to calculate anything.

Important: inside the sensor cable there is a thin air tube that must always stay open. Do not kink or crush the cable. The membrane at the end of the cable must stay in place. If you have to shorten the cable, cut carefully and put the membrane back on afterwards.

In frost: the tank and sensor must be completely empty and dry.

Related questions

What does Fluidy measure?

Fluidy Pro keeps an eye on all the water in your camper: • levels of up to 4 tanks, for example fresh, grey and black water • up to 5 temperatures, for example at the boiler, in the heating circuit or at the fresh water tank • the pressure in the water line • leaks via the leak cable For smaller builds there is Fluidy, more compact and more affordable. Both fit into the same system. More on this in [Tank levels, temperatures, pressure: what Fluidy Pro measures](/blogs/wissen/tankfuellstaende-temperaturen-druck-was-fluidy-pro-misst).

Are the sensors included with Fluidy?

No, Fluidy deliberately comes without sensors, so you only pay for what you really need. Level sensors, temperature sensors, the water pressure sensor and the leak cable are available from us individually. The matching connectors come with each sensor.

How accurately does Fluidy measure the tank level?

Typically to within 1%, relative to the full measuring range. The sensor hangs in the tank and measures how strongly the water presses on it at the bottom. That tells you how full the tank is. Floats or three-stage probes, by contrast, usually only tell you that things will get tight at some point. The calibration in the dashboard guides you step by step, no maths needed.

Can I back up my tank calibration?

Yes. At the very bottom of the tank settings you export the calibration. If you ever delete the tank widget or create it again, you load it back in completely via "Load profile". Best to back it up right after calibrating. Converters use the same calibration for the next vehicle this way.

Does the level sensor work in every tank?

Installation is the same for fresh, grey and black water tanks. The sensor also measures perfectly in stainless steel tanks, because it hangs inside the tank and does not have to measure through the tank wall. You need a 17mm hole at the top or side of the tank, close to an inspection opening. The watertight cable gland is included. Step by step in [Installing the water level sensor](/blogs/wissen/wasserstandssensor-einbauen).

What do I need to watch out for in frost?

Level sensors and the water pressure sensor must be completely free of water whenever there is a risk of frost. If water freezes inside a sensor, it is permanently damaged. So when you winterise, drain the tanks and empty the fresh water system, ideally draining the pressure sensor via the drain tap.

Can I keep using leak detection cables from other manufacturers?

Yes, they can be connected, but we have not tested this. The two contacts of the cable go to + and S on the leak port, polarity does not matter. Our own leak cable is tested for durability and detection. With third-party cables we do not know the coating or construction, so we cannot guarantee that a leak will be detected reliably, now or in a few years.

How does Fluidy detect a leak?

With a 3m leak cable that you lay flat wherever a leak would show up first: under the pump and boiler, along the water installation, at the water filter. As soon as the cable gets wet anywhere, the SmartKnob raises an alarm. With the leak widget, the water pump switches off as well when the alarm goes off. To cover more area, simply connect several leak cables in parallel to the leak port. More on this in [Detecting water leaks: how the leak cable works](/blogs/wissen/erkennung-von-wasser-leckagen-so-funktioniert-das-leckagekabel).

Can I connect several leak cables to one Fluidy?

Yes. Join the cables in parallel, for example with WAGO terminals, and run them to Fluidy with a two-core cable.

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