Water Pressure Loss through Piping

on . Posted in Fluid Dynamics

Tags: Pipe Sizing Water Pressure Loss

Water pressure loss through piping is a common concern in plumbing and fluid transport systems.  Pressure loss occurs as water flows through pipes due to various factors, including friction, pipe length, pipe diameter, and the viscosity of the fluid.  Understanding and calculating pressure loss is essential for designing efficient plumbing systems and ensuring adequate water supply to various points of use.

Key Points about water pressure loss through piping

  • Pipe Length  -  The longer the pipe, the higher the pressure loss.  Pressure loss is directly proportional to the length of the pipe.  Longer pipes result in greater friction losses.
  • Pipe Diameter  -  Smaller pipe diameters result in higher friction losses and greater pressure loss.  Larger diameter pipes have lower friction losses.
  • Flow Rate  -  The rate at which water flows through the pipe (flow rate) affects pressure loss.  Higher flow rates lead to greater pressure loss due to increased friction.
  • Pipe Material  -  The type of material the pipe is made of can impact pressure loss.  Rougher pipe materials create more friction and, consequently, higher pressure loss.
  • Viscosity  -  The viscosity of the fluid being transported (water) affects pressure loss.  More viscous fluids experience higher pressure loss.

The Darcy friction factor can be determined using various charts and equations, depending on the type of pipe and the flow conditions (laminar or turbulent flow).  The Reynolds number is a dimensionless number that helps determine the flow regime and is used to select the appropriate friction factor calculation method.

Properly accounting for pressure loss in a piping system is crucial for ensuring that water reaches its destination with adequate pressure and flow, which is essential for the system's efficiency and functionality.  Engineers and plumbers often use these calculations during the design and evaluation of plumbing systems.


Water Pressure Loss Through Piping formulas

\(\large{ p_l = \frac{ \mu \;  l  \; {v_w}^2 \; \rho  \; SG    }{ 24 \;d \; g }  }\) 

\(\large{ p_l =  4.53 \; l \;  \frac{ \frac{ Q_w }{ C }^{1.852}   }{ d^{4.857} }  }\) 

Symbol English Metric
\(\large{ p_l }\) = water pressure loss \(\large{\frac{lbf}{in^2}}\) \(\large{Pa}\)
\(\large{ \rho }\)  (Greek symbol rho) = density of water \(\large{\frac{lb}{ft^3}}\) \(\large{\frac{kg}{m^3}}\)
\(\large{ \mu }\)  (Greek symbol mu) = friction coefficient of water \(\large{dimensionless}\)
\(\large{ g }\) = gravitational acceleration  \(\large{\frac{ft}{sec^2}}\)   \(\large{\frac{m}{s^2}}\)   
\(\large{ l }\) = length of pipe \(\large{ft}\) \(\large{m}\)
\(\large{ C }\) = pipe coefficient \(\large{dimensionless}\)
\(\large{ d }\) = pipe inside diameter \(\large{in}\) \(\large{mm}\)
\(\large{ SG }\) = specific gravity of water \(\large{dimensionless}\)
\(\large{ Q_w }\) = water flow rate \(\large{\frac{ft^3}{sec}}\) \(\large{\frac{m^3}{s}}\)
\(\large{ v_w }\) = water velocity \(\large{\frac{ft}{sec}}\) \(\large{\frac{m}{s}}\)


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Tags: Pipe Sizing Water Pressure Loss