Need recommendations on a water level switch in a cistern

[MillWeld]

When our garden finally gets underway it will place a demand on our cistern to supply water without pumping it dry and damaging the pump, so a switch to sense the water level is needed. The cistern is 5' deep and has an unused 1" PVC pipe going from the headspace in the cistern to the crawlspace and this is what I would use for running wire to a switch. This run of PVC has two 90 degree elbows and two 45 degree elbows and is probably less than 20 feet. It may be a challenge to run wire thru it but when (if) I undertake it I want input as to the kind if level switch to use: pressure sensing? a tilting or angle-dependent switch? or some other type? I have never installed such a switch before so most any kind of input is OK.
Bob

 

[lilranch2001]

float switch is probably the cheapest, but there are many more technologies out there that can do the job.
You do not mention how east the cistern is to access, and how easy it will be to mount the level switch
One of the ways I have fished wires through pipebesides with a fish tape is to blow a lightweight ball with a string attached through it, does the pvc have hard 90 degree turns or are they sweeps?

 

[dstig1]

Float switch would be the simplest

 

[Rock knocker]

Feed you pump thru a Normally Closed float switch in the tank. When the level drops too much, the float switch will tilt and interupt the pump circuit. The circuit will remain (electrically) open until the level rises enough

 

[MillWeld]

You do not mention how east the cistern is to access, and how easy it will be to mount the level switch
does the pvc have hard 90 degree turns or are they sweeps?

There is no way to mount it; it will have to dangle from a wire, so I guess that mean a float switch?
The ells are hard turns.

 

[lilranch2001]

There is no way to mount it; it will have to dangle from a wire, so I guess that mean a float switch?
The ells are hard turns.

what size PVC?

 

[Willl]

This style has been living in the non-sludge tank on my septic system for 15 years plus without fault.

Would think it's pretty robust.

 

[MillWeld]

This style has been living in the non-sludge tank on my septic system for 15 years plus without fault.

Would think it's pretty robust.

I found it on the web but no obvious place to order it. Where did you get it?

 

[Raspy]

If you can get through the tank wall you could put a probe sensor in and have no wires in the tank at all. The problem with float switches is how to control the overall height of the water. In other words, the level lowers until the switch makes contact, then the contact breaks when the water rises a bit, but not to the full level. One way to work around this is with a time delay relay that keep the pump running for an adjustable amount of time after the float switch rises and opens the circuit. They are easy to install and completely adjustable with a knob.

This way you can put the float switch near the bottom and still fill the tank completely. And do it all with one float switch and no wires in the tank.

This is the setup I'm putting in my water tank for my house. The water level system will turn on the well pump to fill the storage tank. I'll adjust the time delay to get the tank near full.

You can also use this system on the pressure side feeding the house to protect the pressure pump if the tank ever does go dry. The delay relay will limit the time the pressure pump can run on each cycle. If the tank runs out of water the system will lock out until you fix the problem.

 

[MillWeld]

The tank is plastic, completely buried but with an access lid at grade. It captures rainwater and overfilling is no problem because it has a 6inch spill pipe. The only reasonable access for wiring is the 1" PVC pipe. I think all I need is a SPST switch to shut off power to the pump at some minimum water level.

 

[NormL]

One poster suggested blowing a lightweight ball and string down the pipe. Another way I have used is to use a shopvac to suck a plastic shopping bag tied to enough twine to reach the length of the pipe. I tied the twine to the bag using the hand-holds and that way it did not bunch or ball up and stall along the way through. I did this through a 1 1/4" pipe and it worked pretty slick. My run had no bends to negotiate, though, so I can't say for sure that that won't matter. Worth the attempt though!

 

[Willl]

I found it on the web but no obvious place to order it. Where did you get it?

IIRC, I got it locally. Home Depot or Ace hardware I'd bet.

 

[Western]

We had an above ground 1000gal tank, was in place and running when we bought that place. The switch the former occupant used resemble a toilet float shut of ,(float and all), but was connected to the well pump. Worked flawlessly for the 11 years we where there. Wish I had "fiddled" with it some, other than adjusting it for the fill level, then I could give you more input, but it was very reliable and appeared very simple.

 

[biker4jc]

This may be a little over simplifying it, but have you had a look on ebay?

 

[Rock knocker]

.....and has an unused 1" PVC pipe going from the headspace in the cistern to the crawlspace and this is what I would use for running wire to a switch. This run of PVC has two 90 degree elbows and two 45 degree elbows and is probably less than 20 feet. It may be a challenge to run wire thru it......

You may want to give second thought to pulling wire thru pipe fittings versus using conduit and conduit ells. The sharp radius of pipe fittings can result in damaged conductors

 

[MillWeld]

I found a switch made by Dwyer with 30 feet of PVC cable for $25. I plan to lube the cable with wire-pulling grease and have someone push as I pull. Think that'll work?

Series CFS2 | Cable Float Switch | Dwyer Instruments

 

[lilranch2001]

Dwyer makes good equipment
With 1" pipe and if you lube it up well, and push athe same rate you pull, I would think it should be ok. Just make sure the puller is not overly aggressive.
Not the perfect solution, but I think viable.

 

[radioman]

you mean this? LITTLE GIANT Switch, Automatic Float - Float Switches - 3VA90|RVMS-10 - Grainger Industrial Supply

Do you know anyone with a pedestal sump pump that is broken? you can take the float and switch off the top and rig up what you need in the cistern. when you setup the rod trip - you can set it so it trips on when water level is high enough and leave power on and let your pump switch determines if it needs to pump or not, but off when it reach the lowest point you want power off.

 

[Redneck in training]

I found a switch made by Dwyer with 30 feet of PVC cable for $25. I plan to lube the cable with wire-pulling grease and have someone push as I pull. Think that'll work?

Series CFS2 | Cable Float Switch | Dwyer Instruments

There is one more thing to consider. Most float switches close when level is low but you need the opposite function. You need SPST, NC or SPDT. I would recommend to get SPDT Then you can have it either way.

 

[Qapla]

Have you considered using some sort of float mounted inside a piece of PVC pipe. You could extend the PVC inside the tank so that it comes just short of the bottom. The water level will fill the pipe the same as it does the tank.

You could put a fishing float with a weight on beneath it hung from a switch mounted above the ground/tank. When the level gets low enough, the weight would pull on the switch and turn the pump off. When the level is up, the float would support the weight and allow the switch to turn on allowing the pump to run.

Just a thought ...