# Pipe Diameter and Pressure

#### P00HB33R

##### Senior Member
Hi Guys,

My scenario is as follows: My new house has a main water connection of 25mm with about 4 bar pressure.

They installed a 32mm pipe that runs from the main connector to my house, which is roughly 100m away (its a plot).

What would be the pressure drop, if any, by using the 32mm pipe, and also, if the other end has a 32mm to 25mm reducer would this up the pressure back to the starting point?

Thanks guys.

#### wetkit

##### Expert Member
Ok, so from the main line to your house is 100m 32mm pipe?
You will only see a pressure drop when you using water. No water flow, no pressure drop.
The pressure drop would depend on how much water you using at any one time.

#### P00HB33R

##### Senior Member
Ok, so from the main line to your house is 100m 32mm pipe?
You will only see a pressure drop when you using water. No water flow, no pressure drop.
The pressure drop would depend on how much water you using at any one time.
Hi Thanks for the reply. Lets say for argument sake, a tap directly connected to my main, at the source, pumps out 4 bar. If I move the same tap past the 100m x 32mm pipe, behind the 32mm to 25mm reducer, would that same tap still have 4 bar?

#### ElecEng

##### Senior Member
what volumes of water m3/h are you expecting to be using? If you don't tap off the 32mm section you won't see an effect

#### P00HB33R

##### Senior Member
I really have no clue about the volumes, but the pipe is going to be used only to supply the house. We have a borehole and pressure pump for irrigation (check the fancy word for "watering the lawn and garden" hehe)

#### MyWorld

##### Executive Member
The pressure will drop further according to Bernoulli’s Principle.

There will be a drop form the 25mm to the 32mm and then another drop from the 32mm to the 25mm again. By how much, you will have to calculate it yourself.

http://www.dummies.com/how-to/content/use-bernoullis-equation-to-calculate-pressure-diff.html
http://www.nptel.iitm.ac.in/courses/Webcourse-contents/IIT-KANPUR/FLUID-MECHANICS/lecture-14/14-6_losses_sudden_enlarg.htm
http://www.irrigationtutorials.com/using-a-smaller-pipe-to-increase-water-pressure/

That being said, the drop in pressure would be negligible.

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#### P00HB33R

##### Senior Member
Thanks guys for all the answers. I'm feeling a bit better now. Was really stressing the pressure. Me likes a nice shower that almosts takes the skin of the back