Well pump slow down


Lately my well pump has been taking a long time to get to shut off pressure. When I am using 8 -10 gpm running my geothermal heat pump, the normal duty cycle of the pump was about 66% i.e. it ran for 4 minutes to get to shut off(60psi), then for 2 minutes to get to turn on pressure (40psi). This has been the case for the last 10 years. Now the off time is still 2 minutes but the pump runs (at 8-10gpm) for upwards of 45 -60 minutes before it reaches shut off pressure. Also, before I could run 18-20gpm steady and pump would hold 55 - 60 psi. Now the best it will do is 12gpm steady but pressure will not get above 27psi. Pump is a 1hp submersible Gould 10GS 3 wire with a controller and 80gallon pressure tank. Pump amp drain is normal at 10.2amps. Well is 200ft deep and a water level at 40 ft. and was rated at 40gpm when drilled 10years ago. Pump is at180ft. Terrain is granite and I have never had any problem with water supply; lake is 100ft away and 50 ft below well head. Pressure in system holds at 60psi when not used or pumping. Water is moderately hard with moderate level of iron bacteria. No sediment.
People, could you give me your ideas on what might be going wrong here?
Pump was replaced after first 5 years due to motor winding failure. Now its another 5 years and trouble again. Same model of pump. Is it the type or brand of pump? (assuming I have a malfunctioning pump)
At this time of year, it is not unusual for the heat pump to be running 24/7 for days on end. In a normal winter, the heat pump may be on 50% of the time for 3 -4 months. So a lot of pumping but I understood this pump should be up to it. But maybe I'm misinformed???? Is this kind of problem a normal failure mode after heavy use?
Thanks for your input!
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Treetops wrote:

I can't think of any cause other than a pump problem. A pump should not fail even under your hard service use in just 5 years. From the description it sounds as if the impellor stages are failing.
Harry K
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Harry K wrote:

Hmmm, after thinking a bit, a partial blockage somewhere in the pipe leading to the tank could do it. I still suspect the pump though.
Harry K
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Harry K wrote:

but the output pipe might be partly frozen.
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snipped-for-privacy@yahoo.com says... |Harry K wrote: |> Harry K wrote: |>> Treetops wrote: |>>> Lately my well pump has been taking a long time to get to shut off |>>> pressure. I had a similar problem. I also saw a huge increase in monthly electric usage. The pump impellers were chewed up.
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