1/2hp water jet pump struggles w low water levels

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Tangerineman

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The water level of our lake changes by over 4 feet by October. Our cottage is about 20 feet above the water level by then and about 75 or so feet away from the shore. Our 1/2 hp jet pump stops being able to attain proper pressure and turn itself off by October 1st.

Would a 3/4 hp pump solve this problem? I see most 3/4 pumps have the same recommended maximum height of 25', and one says it will work with a 90' drop.

We've thought of moving the pump further down the slope to the lake (and wonder if that would work) or should we just get a stronger pump?

Would a 3/4 pump be a lot noisier? Currently the pump is under the cottage. Thanks so much for any thoughts!
 

Valveman

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24' of lift is max for any shallow well jet pump. You can use a two pipe jet when water gets deeper than 24'. A submersible would be better if it is allowable in the lake. But if you have to stay with a jet pump, a larger pump and moving it closer to the lake level will help.
 

Tangerineman

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Thanks valve man, the lake freezes up in the winter so a submersible is out of the question.

I'm just back from a local hardware store where I purchased the pump, and it was suggested my problem at this moment might be a pebble or rock has been sucked into the (I forget the name, maybe the header? It is where the water first enters the pump). I can cycle the motor on and off to try and clear it, and take it apart to see if something has become stuck. The needle on the pressure gauge is doing a lot of vibrating as it nears the max pressure.
 

Valveman

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The pressure gauge bouncing is because you have low NPSH from trying to suck water from too deep or the inlet screen is clogged. It wouldn't build but 20-30 PSI if you had a rock in the jet or venturi nozzle. Moving the pump closer to the water level would help.

A submersible under the ice won't be hurt anymore than a foot valve under the ice. Either way it is the pipe coming through the ice that must be kept from freezing. You could even use a bleeder orifice above the submersible that would drain the pipe every time the pump shuts off.
 

Tangerineman

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Im going to put something over the foot valve to keep grit out. Do you think a simple nylon stocking would work or are the foot valve socks ($12) a wiser choice?

Turning the pump on and off several times seems to have cleared the situation up. There must have been sand in the system.

I'll see how late into the fall the pump keeps working and either move my pump closer to the water or look at 3/4 hp pumps. If I move the pump it will cost about as much to build a shelter for it as buying a 3/4 I can keep under the cottage.
 

ThirdGenPump

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When I set them in ponds I usually use 8-10 square feet of aluminum window screen wrapped/bundled around the foot valve. The larger surface area the better off you are.
 
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