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#1 New.Canadian.DB.Owner OFFLINE  

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Posted September 18, 2014 - 03:37 PM

Not often one gets to mix these topics into one question, but the principle applies to all of the above.  If I decrease my pipe diameter, does the pressure increase or does the flow rate increase?

 

My well pipe is leaking between the house & the well.  It is 1 1/4" ID pipe, so I shoved a 3/4" ID pipe through it & connected it to the 1" pipe coming from up the well.  I know I had 60 psi peek in the 1 1/4" pipe, but what will the pressure be in the 3/4" pipe?  I bought 100 psi potable water poly-pipe, so I hope I am on the safe side.


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#2 toomanytoys84 ONLINE  

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Posted September 18, 2014 - 03:53 PM

I am in no way shape or form able to answer that question with certainty....I am talking out my butt.  If someone knows right or wrong please explain.

 

 
Bernoulli's principle

 

In fluid dynamics, Bernoulli's principle states that for an inviscid flow of a nonconducting fluid, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.

 

Your speed would increase through the smaller pipe

 

Your pressure would decrease not increase.

 

As Velocity increases pressure decreases

 

http://flexpvc.com/W...nPipeSize.shtml

 

my concern is your lose of GPM.  You went from 62GPM to 23GPM of available flow through the pipes.

 

That is quite a substantial drop if you are using this to supply your home.


Edited by toomanytoys84, September 18, 2014 - 04:13 PM.

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#3 DougT ONLINE  

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Posted September 18, 2014 - 04:02 PM

You are still going to have 60 psi in the line. You just won't have to pump as much water to reach it. It will cut the flow rate and volume.


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#4 petrj6 ONLINE  

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Posted September 18, 2014 - 04:14 PM

:ditto: :yeah_that: :iagree:  Your pressure will not increase beyond what your pump can handle, not so you would notice anyway.  but your gpm or volume will decrease, that would be your only concern.  Good question thou!

                                                                                                    Pete


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#5 KC9KAS OFFLINE  

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Posted September 18, 2014 - 04:52 PM

A smaller diameter pipe will have more friction loss resulting in less flow (volume) for any given pressure.

 

A rule of thumb...As pressure increases, flow decreases...Think a high pressure washer.....3000 PSI and only 2 GPM's


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#6 ol' stonebreaker OFFLINE  

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Posted September 18, 2014 - 05:00 PM

You've lost about 40% of your pipe area, however frictional loss will be a lot less in poly pipe than in 3/4" iron pipe. It's worth a try. If you lose too much flow there might be some digging in your future.
Mike
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#7 Coventry Plumber OFFLINE  

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Posted September 18, 2014 - 05:01 PM

You should have a well tank in the house that stores a reserve so your pump doesn't kick on every time you open the faucet so unless you use a large amount of water at one time you probably won't notice any difference.plus well pipe is always connected with internal barbed fittings so the way you connected it is not as drastic as u think. The normal fittings reduce the size a little anyway.the well tank regulates the pressure in the house ,the pump just pumps till its told to stop.
I hope that helps and makes sense.
Tom
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#8 JDBrian OFFLINE  

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Posted September 18, 2014 - 05:09 PM

 When you draw water there will be a pressure drop. The more friction in the pipe the more pressure drop you get for any given flow.  It just means that your pump may run a little longer to bring the tank up to pressure. It may work just fine. You'll just have to try it and see. 


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#9 New.Canadian.DB.Owner OFFLINE  

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Posted September 18, 2014 - 05:51 PM

Thanks to everyone who replied.  Guess I should have mentioned the end of the new pipe inside the house is connected to a 1/2" pipe that feeds the whole house.  I expect that limits my flow rate more than the new 3/4" pipe.  You all made me feel safer about the choice to go with 3/4" poly over digging a new line.  I still like the safety margin of the 100 psi pipe over the cheaper ($20 less) 70 psi poly.


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#10 TAHOE OFFLINE  

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Posted September 19, 2014 - 07:21 AM

My mom's house I am moving into used to have a 1" coming in. When they drilled the new well, the just ran 3/4" all the way from the well, it's probably close to 200' away from the house. We have pump set at 30/50. I have 3/4" PEX out of the pressure tank to a 6 port manifold which then reduces it down to 1/2" for the house. I have been used to well pressures all my life so guess I don't notice if it's an issue or not.


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