Author Options:

How much water is in my cistern? Answered

I built a 33 gallon cistern my garage to collect condensate from my HVAC system. (I didn't have room outside my condo for a rain barrel). It has a spigot and a short hose, it lives above my utility sink, which is where the overflow goes when the cistern is full.

I'm hoping some clever makers can give me some ideas on how I can build something that will tell me how much water is in the cistern. I have Samsung SmartThings so I've considered putting a water sensor just below the overflow hole, so I will know when it's at 100%, but I would prefer to have a percentage reading and an alarm when it gets to 90% or so. I considered an arduino with an ultrasonic sensor but that a bit involved... Not opposed to it but please be prepared to hold my hand thru the process of you propose it! ☺. Non-SmartThings solutions also welcome.

Thank you - looking forward to your genius ideas!!




23 days ago

A lot depends on your skill set.
Commercial water level gauges are available at reasonable cost. (see amazon for example)
in manufacturing your looking at contact or non contact methods. Contact: float and either a potentiometer to give an analogue reading or a switch to give a simple full or empty light.
Non contact - you could look at ultra sonic sensors or even lasers but in most cases the vessel is simply weighed.

I would buy a level alarm.


24 days ago

There are water alarms. Electrical continuity thru water sets off alarm. Sold for use in basements.

Jack A Lopez

24 days ago

Maybe you could put a weight measuring device underneath your, what you call, "33 gallon cistern?"

You know, gravity in your garage probably doesn't change that much, so a measurement of weight would be accurate proxy for measurement of mass.

Here is a Let's Make search for "HX711"


which is the name of an IC in a popular module, used via Arduino, that the kids here seem to be using for this purpose of weighing things.


24 days ago

Siphon gauge
Clear tubing goes out of top, down to bottom, back up. Sort of a sideways "S" You can read level in the tube as it returns toward the top.


26 days ago

Drill a hole on the side near the bottom, slap in a 90 deg elbow and clear pvc tubing up the side.
If you pop in a few drops of food coloring its easier to read the water level.

main setup.JPG

27 days ago

There is always old school technology....
A small hole in the top and a float for example.
Back in the day water tanks had them with a pulley on the bottom of the tank.
A string on the float goes through the pulley and outside to a vertical scale.
The same way the float moves up or down the weight on the cord will move as well.
All it takes is to put the weight at the water level to be accurate ;)