I drained my fresh water tank and forgot to turn off the pump. Might have ran dry for almost a day before I found it. It still pumps but I was wondering how much damage I did.
The RV water pumps have a Thermal overload built in. They will run until the motor temp kicks the motor off and once it cools down will run again, so the pump rarely runs full time when the tank is empty. This helps prevent pump failure. But letting this go for days or weeks will destroy the pump unless you have no shore power and the battery eventually goes dead. Doug
Mine ran dry for more than two days and it's in a confined area. It was warm to the touch (just warm) and has continued to work perfectly during the five years since.
I don't think the pumps will be damaged running dry. Now running it for a full day under any circumstance will take how ever many hours of the life of that pump I would imagine!
I just installed a Flojet Sensor VSD 4.5GPM Pump.
Here's a pic of the box:
Now, this is the owners manual. Notice bullet item #7 - Self priming / Runs Dry:
The pump is most likely the rubber bellows type. Since it is just rubber flexing, it does not hurt it to run dry. OK, maybe you consumed some of its life just because of the hours put on it, but no specific damage for it running continuously.