Groundwater and Foul sump monitoring system

Hello all, thought I'd share my latest project with you. We are building a new home with basements, and as part of these basements we have installed sumps for groundwater and foul waste. UK building regulations stipulate that you must have a high level alert system, i.e. when the big holes in the ground fill up and the pumps have stopped working you need to be notified.

Rather than using an off-the-shelf box which has an input for a float switch (BORING) I decided to install ultrasonic distance sensors in each sump (and a temp / humidity sensor because... why not)

All tied together with various 3D printed parts - including 3D printed nuts and bolts (!), an Arduino Mega, Node RED, and data logging with Influx and Grafana.


Looks good - which ultrasonic sensor did you use ?

I am using one of the waterproof single transmitter/receiver units for monitoring the water level of our tanks.

The problem i have found is that is has a minimum distance range of approx 20cm so i have a dead spot once the water is above that level. I assume you have tested yours and do not have the same problem ?



Hi @craigcurtin, looks like I used the same sensor as you - the JSN-SR04T. (I started with the HC-SR04 and two months later it was caked in rust and had stopped working.)

First thing I noticed was the minimum distance, which was 203mm. The way I got around that was to 3D print a riser tube to go on top of the mount. (See the screenshot of the mount which has 3x parts, it's the top right little tube, which stacks onto the right hand arm, which then mounts onto the left hand diagonal bracket which bolts into the lid of the sump.)

In normal operation, the water level in our sumps would not get high enough (near to the lid where sensor is mounted) to be a problem, but we have a temporary (cheap) pump in use during building works, and the water does get a bit higher hence the riser tube.

I have to say the sensor-in-a-pipe thing works quite nicely. I found that with a 32mm pipe (internal diameter 32mm) it works, but the first version of my grommet was such that the opening was about 30mm and this resulted in dodgy readings. But the 32mm opening works reliably. The point of the grommet is two-fold: to hold the sensor securely pointing exactly downwards (i.e. exactly 90 degrees), and to provide something to wedge the pipe on to.

THats interesting - i went through a whole series of steps - started with a 50mm riser, then went to a 75mm and then finally a 90mm and could not get consistent readings - i thought i was getting reflections from the sides of the pipes continually - tried everything - in the end i lined the inside of a 90mm pipe with some carpet for marine use and still did not work - in the end i admitted defeat and just mount the sensor flush to the top of the tank and do not care if my max reading is 87% (its a fresh water rainwater tank so more concerned when the levels go low rather than high - based on what you have said i might have to try and revisit it



Let's just hope you never hear the "Pump fail" alarm!

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