Sensing water level in cistern

   / Sensing water level in cistern #11  
The cistern is used for watering a garden. The pump is turned on manually via switch; if they fail to notice a low level in the tanks the sensor will cut the power. The pump is already in place (external to the tanks) so the added expense of an in-tank pump is to be avoided. I appreciate all the suggestions.
The one I posted doesn't care where the pump is. Just drop the float in the sistern or riser
 
   / Sensing water level in cistern #12  
Yep the float switch is the way to go. They will live an easy life in a cistern. A lot are used for sewer ejector pumps. Their is nothing magic about them- you should have no difficulties making it work for your needs.
 
   / Sensing water level in cistern #13  
The Cycle Sensor does the same thing as a Pumptec, except that it will work with any pump (jet pump) as it doesn't have to be installed in a submersible pump control box like the pumptec. The Cycle Sensor is also a lot more sensitive and adjustable than a pumptec. Plus there is no float switch needing to be installed inside the cistern. The Cycle Sensor simply looks at amps and knows when the pump has run dry.
 
   / Sensing water level in cistern
  • Thread Starter
#14  
I may have to go with the float switch Prichard recommended (that's what I have in my cistern) but my friend draws on his tanks one at a time (one valve closed) so that would require 2 floats switches (unless he changes his mind). I was hoping to get ideas to utilize the narrow riser pipe, e.g. put an opaque float inside the riser pipe that interrupts a light beam when the water falls to a predetermined level. Maybe that's too complicated.
 
   / Sensing water level in cistern #15  
It sounds like you'd want two float switches, and some way to connect them to the valve position so that only the switch in the tank that the valve is drawing from will switch the pump.

I am starting to see what you are doing with the riser, you are trying to sense height from the pump side of the valves, it eliminates a lot of electric logic. Another advantage of doing that is if both valves are off, then there is no volume in the riser and the pump won't run.

Simplest "empty" float switch I have seen is a tube with a rising float (hollow tube a little smaller) that triggers a microswitch (can be any kind of switch, including optical). If the tank is empty, the float is on (near) the bottom and the switch closes and lights a signal (you could have it either open power to the pump directly, or trigger a relay). As soon as the float is high enough to turn off the signal (let the pump run, etc) it hits a stop. Water can keep rising as much as it wants after that, you don't care--you don't need it to tell you how much water is there, just "more than enough". Example is from a simple consumer grade humidifier.

Other nice thing about this system is the float is tall enough that the switch itself is well away from the water. No reason that couldn't be a rod that sticks up attached to a float, rather than a tall float. Total travel is about 1/2", if that.
 
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   / Sensing water level in cistern #16  
Yes you're over complicating it. What size is the riser? How deep?
 
   / Sensing water level in cistern
  • Thread Starter
#17  
GLyford, I have seen the tubes with a rising float but I don't have the headspace to insert them, and the ones I have found what I have seen are too short. The cisterns (and riser) are at least 3' tall and maybe a foot of headspace above them.
 
   / Sensing water level in cistern #18  
So put in a stack of 6" tall floats. They only need to float enough to say there is still some water there, not to say that the tank is full.

Just make your stop strong enough to keep them in the tube.
 
   / Sensing water level in cistern #19  
Here's another idea: How about a float flexible enough to bend into that space, but still stiff enough to work? I'm thinking a pool noodle if your riser is big enough.

If your riser is smaller than that, how a bout a capped or plugged section of garden hose?
 
   / Sensing water level in cistern
  • Thread Starter
#20  
So put in a stack of 6" tall floats. They only need to float enough to say there is still some water there, not to say that the tank is full.

Just make your stop strong enough to keep them in the tube.

Hmmm... can the electrical connection be submerged?
 
 
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