Switch to turn off water pump when water supply interrupted

[Daxbuddy]

Hi. In our Mexican hideaway, we have a small cistern that gets filled with city water. This feeds a pump which keeps a 10 gal pressure tank filled when city pressure declines. Recently we discovered our cistern had run dry, and the pump was churning away (dry) trying to fill the pressure tank. The cistern has a simple float that allows it to be filled. I am told I can get/install a switch from that float that would prevent the pump from running if the cistern runs down too far.
I don't know the terminology for this switch, but would like to research it, buy it and hopefully install myself. Qualified pros around here are booked out for weeks. Advice on sites, youtubes or similar appreciated.
Tnx

 

[AC Power]

You need a float switch. They have them at Home Depot.

Model #EBFSWPB

You need a float switch that will OPEN it's contacts when it hanging by way of gravity only....no water floatation. This way, the float will permit the operation of the upstream pump motor (with it's existing controls, if any) provided the device is floating in water....hence, no water = no floating = pump motor cannot start.

BTW: Your pump motor might be fine, but the pump itself could be dead now. Pumps should not be operated dry.

 

[theknobs]

Yes, you need a separate float switch - a switch won't work off your existing float because that float has a different range of operation. Its purpose is to keep the tank full, so it operates at the high water level. The float switch you need will have to operate at the empty level.

 

[AC Power]

Correct. Many of these sump pit pump we connect actually have multiple floats. A low level cut-out MOTOR OFF float, a mid-level float (to MOTOR ON/OFF a secondary pump if the first isn't keep up (or its dead), an upper MOTOR OFF float, and an emergency-high limit float to provide audible/visual devices (many of what are remote) to indicate a pending overflow. Some of the more complex can away with a float, and replace it with an alternator, that is, a device that brings pump 1 of the first dump, and uses pump 2 for the second operation. This way, either pump gets use (prevents seizing), and the alternator can bring BOTH pumps ON if one working pump cannot keep-up with demand. Phew....anyways, that what I know.