Pump won't shut off

[Tedr]

I'm trying to decide if I need to replace my pump. I don't know how old it is, but I think it may be only a few years old.

I am drawing water from a lake. The pump is a Mastercraft 3/4 hp. Vertical lift from the lake to the pump is about 12 feet. The pressure tank is at the cottage about 100 ft up a 45 degree hill. The system had been running fine. The pressure guage at the tank when full was 40 psi - not sure what the pressure at the tank is when the pump normally kicks in, pretty close to zero.

Last night the connection at the pump worked itself apart, the pump lost prime and was probably running continuously for some time (we can't hear it running unless we are down at the lake). We repaired the connection and primed the system. The pump is able to get the pressure up to 35 psi but no higher, and the pump won't shut off. For the time being we are manually shutting the pump on and off as needed.

I'm guessing that the pump may have been damaged by running dry for a period of time. Would it more likely fail completely, or would it pump water but with reduced efficiency in such a case?

Thanks,
Ted

 

[Valveman]

You probably melted the impeller. It could also just be something clogging the jet nozzle, but I doubt it.

 

[Sponsor]

 

[Tedr]

Thanks Valveman. I'm planning to open up the pump, clean out the nozzle and inspect the impeller. I'm also going to reposition the foot valve - I think it is picking up sand and silt. It makes sense to me that the nozzle would be partially blocked. I'll let you know when I get back.

 

[LLigetfa]

Given the elevation you describe, you should consider putting a submersible in the lake. It will give you much better pressure and use less electricity.

 

[Tedr]

Valveman: I didn't need to take the pump apart. I thought I should look after the foot valve problem first so I cleaned up the foot valve and repositioned it so it wouldn't be so close to the bottom. After that I ran the pump and it ran well enough to reach shut off pressure. Maybe the process of priming the pump and drawing cleaner water flushed the nozzle. Other than that, I have no clue what might have changed the situation. In any event, it seems to be working as well as it ever did so I decided not to open up the pump. Thanks for your help.

LLigetfa: I'm not sure why, but the former owner chose a jet pump over a submersible. But when this pump fails I will definitely consider a submersible. I had a jet pump at my previous property but that was on a sand point well. Thanks for the suggestion.