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Back Pressure Created

Back Pressure Created

Back Pressure Created

(OP)
I am trying to determine how much back pressure is created on a pump per a given decrease in discharge line diameter. In this case the pump is a motor driven diaphragm pump rated to 85gph and 145 psi with 1" suction and discharge. The injection point line pressure is 100psi and approximately 10ft away. I want to use a 1" corporation stop which has 1/2" OD quill, effectively reducing the pipe size from 1" to 1/2". How can I calculate the back pressure that will be put on the pump? I need to determine what I can "get away with" without overamping the pump motor.

RE: Back Pressure Created

Back pressure is not important to positive displacement pumps. Positive displacement pump provides an approximate constant flow at fixed speed, despite changes in the back pressure. Changing back pressure on a positive displacement pump results in minimal changes to flow.

Designers usually size the piping on PD pumps for a flow of 3 times the average because the flow from PD pumps is not constant due to the stroke of the pumps. However, the low flow for your application does not seem to be significant enough to generate a large back pressure.

Your backflow will basically be the 100 psi line pressure that you are pumping against.

You have not provided enough information to estimate the headless throught the quill. If you desire to determine the actual pressure drop through the quill, your best approach is to request it from the manufacturer of the device.

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