small (gardening) pumps

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  #1  
Old 10-15-04, 11:45 AM
JohnD
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Help with some small pumps

I'm designing a plant watering system for a project in school. Basically, I'm using some small windsheild wiper pumps to water each plant. The problem is, if i turn the pumps and then turn them off, water continues to flow. The pump is located at the bottom of the tank, so im thinking that the pressure from the tank is causing water to flow even when the pump is off.

I've tried positioning the pump above the tank level and connecting the tank and pump with a hose, but the pump isnt strong enough to pull water up into the input. How can i keep water from flowing when the pump is off? My setup is low pressure, low flow, so i dont need anything heavy duty.

Thanks for any input.
 
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Old 10-15-04, 12:11 PM
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I don't understand why the pump is not strong enough to pull up the water from the tank because the reservoir in a car is lower than the pump. As far as the water continuing to flow after the pump is shut off.....is the end of the hose lower lower than the water in the tank? Could be a siphoning problem. Try raising the end of the hose above the water suppy level. Good luck and post back. And by the way, welcome to DIY.
 
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Old 10-15-04, 01:34 PM
JohnD
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Well, I looked under the hood and they are set up so the pump inlet is conencted to the bottom of the tank so water is always forced into the inlet. I connected a hose to the pump inlet port and put the hose in the tank, but it wont pull the water up the hose. These pumps must not be meant to pump air, only water. I've tried raising the hose up, but if the rest of the hose is not elevated as well, water still flows.

Is there any type of device that would resist the force of the water in the tank, but still alow water it flow when forced through by the pump?

Thanks for the welcome.

JohnD
 
  #4  
Old 10-15-04, 01:50 PM
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You may have to switch to an aquarium pump. Sorry but thats all I can come up with.
 
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Old 10-16-04, 05:05 AM
Gotcha
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Hey John. What you need is an automotive check valve to put in the line running to your plants to shut off the flow when the pump stops. Should be able to pick one up at any auto supply store. Good luck with the project!
 
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Old 10-16-04, 10:34 AM
JohnD
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Thanks for the replies. I'll look into the check valve today. If i understand correctly, the valve will block flow until enough pressure is applied?

As i understand it, a check valve prevents back flow. I need to prevent flow in the same direction as normal flow when the pump is turned off.

Thanks
 

Last edited by JohnD; 10-16-04 at 11:01 AM.
  #7  
Old 10-17-04, 10:55 AM
JohnD
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I was thinking, maybe i could shut off flow with a solenoid valve that closes the line after the pump turns off. Does anyone know where I could get a small, cheap solenoid valve for around 1/4 inch diameter lines? This system is VERY low pressure, so the cheapest valve possible is what im looking for.
 
  #8  
Old 10-17-04, 11:13 AM
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What you might try. Assuming you are using an open tank. Place a tee with an elbow just above the water line in the line going to the plants. This way when you turn the pump on you will have flow to the plants but also back into the tank. This will also create an air gap to stop the water when you turn the pump off. I have never see nor heard of a CHEAP solenoid.
 
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Old 10-18-04, 05:21 PM
JohnD
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im beginning to think maybe i just need different pumps. Are there pumps that can have a hose connected to the inlet, have the hose in a bucket of water, and pump the water (vertically) up the hose into the pump and then out?
 
  #10  
Old 10-18-04, 05:29 PM
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There are various pumps at your local garden center, pet store,home center, and large discount stores.
 
  #11  
Old 10-18-04, 06:35 PM
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JohnD,

You can make what you have work if the tank and pump is installed lower than the outlet to prevent syphoning.
 
  #12  
Old 10-20-04, 06:20 PM
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How long does the water continue to flow after you turn the pump off?

The pump motor will continue spinning for a short while after the power is turned off. Also, the water flowing through the tubing has mass and inertia so if you get the water moving it will stay moving for a short while after you turn the pump off.
 
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