Does a pump face less back pressure if a vertical pipe is wider?

[Ray F]

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I've worked at sea for a number of years and now I'm particularly interested in learning more about fluid dynamics in order to find practical solutions to environmental problems. I would be very grateful for any advice people on this forum can give me.
At the moment I want to pump water up to the roof of a house. My question is this: will a pump that pumps water 10 meters up a vertical pipe of 10 mm Inside Diameter face less back pressure pumping the same water 10 meters up a pipe of 20 mm Inside Diameter? Or is the back pressure the same? Thank you for your help.

 

[erobz]

How did you find PF?: google search

I've worked at sea for a number of years and now I'm particularly interested in learning more about fluid dynamics in order to find practical solutions to environmental problems. I would be very grateful for any advice people on this forum can give me.
At the moment I want to pump water up to the roof of a house. My question is this: will a pump that pumps water 10 meters up a vertical pipe of 10 mm Inside Diameter face less back pressure pumping the same water 10 meters up a pipe of 20 mm Inside Diameter? Or is the back pressure the same? Thank you for your help.

At the same flow rate in each case?

 

[hutchphd]

It depends upon the flow velocity and perhaps the surface roughness of the pipe. Here is a good simple treatment https://en.wikipedia.org/wiki/Friction_loss
The middle part is excellent, in my opinion. Please ask questions as necessary

 

[Baluncore]

Welcome to PF.

Or is the back pressure the same?

To pump water upwards, you must overcome both the hydrostatic pressure, and the resistance to flow in the pipe.

Hydrostatic pressure is a function of height only, not of diameter.

The added back pressure, due to the resistance to flow, is due to wall friction of the water flowing in the pipe. It will be less for a bigger diameter pipe, but that back pressure will be dependent on the flow rate and the pipe details.

 

[Joe591]

The bigger pipe will put less back pressure on the pump for the same flow.

 

[sophiecentaur]

The bigger pipe will put less back pressure on the pump for the same flow.

As demonstrated by the fact that central heating (water) central heating often uses large bore pipes (according to a number of rules of thumb) according to the flow of water they need to take. I quote central heating because the system pressure is usually only a bar. Cold water supplies are straight off the mains and tend to use 15mm pipe throughout. Copper is too expensive for plumbing to be over generous with large bore pipes.