sump pit water level

I am looking for a way to measure water level in a sump pump pit. actually have 5 pits.

step 1 is to monitor water level in each pit and datalog

step 2 is to attempt to maintain water level

but for step 1, the sensor is needed I have been reading about capacitive sensors, a tube in a tube with insulator in between looking for information on how to select insulators from easily available parts. pvc pipe, plastic sleeve, heat shrink, etc.

any suggestions ?

also, will copper pipe that oxidizes, will that effect the operation ?

An ultrasonic sensor looking down at the water surface is sometimes the best solution. If you can position it so that an overflow can never immerse the sensor then it will work reliably and more accurately than most other methods. The distance to max and min water level must obviously fall within the range of values that the sensor can measure - some are good close up, some are good at longer distances.

Metals like copper in constant contact with the water can be a problem for some sensing methods. If it's capacative then corrosion on the copper won't affect the measurement until it builds up thick enough to swell the pipe.

when it comes to measuring liquid level there are lots of different ways. A few things to consider is liquid surface conditions, corrosive affects, space to mount sensor, resistance of product, solid matter in liquid, temperature, etc, etc.

morgan has a good idea as long as you have no pipe or drain that's emptying into the sump above the water level. they like smooth liquid surfaces, low liquid temperature and no splashing near the sensor.

Capacity sensors are nice (never tried to build one) but they do not like thick floating solids that tend to stick to the probes. A capacity probe will not have any metal touching the liquid so that shouldn't be a problem.

typical capacitance sensing in some cases do not need physical contact.

I wonder if just the presence of water in close proximity might create a measurable effect?

luckily, the water is clean and probably better than tap water.

I wish there was a single cone ultrasonic, like the $10.-- measuring units. the dual head are not as conducive to these projects. not sure why no one is offering these. especially since they are so cheap in an ultrasonic measuring device.

Because a single transducer can't chirp and listen at the same time. When you want to measure small distances like 5-20cm this is a problem. Longer distances can use a single transducer.