Open and Closed Water Systems: Applications and Design Equations

There are two main water systems types that are used for most engineering design and calculations: pressurized (or closed) pipes for water distribution and non-pressurized (or open) pipes for water collection.

Pressurized pipes are typically used for water supply, and they get their name from the fact that the pressure for any cross-section along the pipe, the pressure difference between the top and bottom of the pipe does not vary (except for the elevation head). In these types of systems, pressure is lost as water travels along the pipes due to friction. The pressure is typically supplied by a pump or simply by gravity itself, depending on the elevations of the start and end of the pipe.

In contrast, non-pressurized pipes are typically used for wastewater and they get their name from the fact that at least one pipe end is open to the atmosphere and therefore under atmospheric pressure. In these type of pipes, pressure changes both vertically across a cross section and horizontally (also due to friction) as the water travels along the pipes. Under non-pressurized conditions, water will flow from the highest to the lowest elevation as a function of the pipe size, slope, diameter and material.

Three common equations that are used for design of open and closed systems are: Hazen-Williams Equation, Mass Conservation or Continuity Equation and Manning’s Equation. The Hazen-Williams Equation is mostly applied in closed systems and it establishes a relationship between the volumetric flow rate against the head loss, pipe diameter, and the Hazen-Williams Coefficient, which varies depending on the pipe material. The equation gets the name after its developers, and it is commonly used for design of water supply, fire sprinklers and irrigation systems.

The Mass Conservation or Continuity Equation is a simple yet useful relationship that can be used both in open or closed systems. The formula is based on the fact that water is incompressible and the volumetric flow rate going through any point in time must be directly proportional to its velocity and the cross sectional area. Mass is always conserved in fluid systems regardless of their complexity and flow direction. What is also useful about this equation is that it can be used to compare the areas and velocities of two different pipes. When continuity exists, the mean velocities at all cross sections having equal areas are then equal, and if the areas are not equal, the velocities are inversely proportional to the areas of the respective cross sections. This is further shown in Figure 3 below.

Last but not least is the Manning’s Equation, which is the most popular for open water systems. It is used to calculate the velocity of a fluid flowing through a partially full pipe. Once the velocity is known, the flow can be calculated using the Continuity Equation. The equation is based on the fact that the flow through an open conduit is directly proportional to the flow area and slope (or energy loss), but indirectly proportional to the Manning’s coefficient and the wetted perimeter. The Manning’s coefficient is based on the pipe material roughness and is dimensionless

There are plenty of online resources out there that can further complement your reading when understanding how these equations are applied.  You may also reach out to me via LinkedIn to learn more or simply get in touch!

By: Salvador Bentolila, PE, ENV SP
Disclaimer: I do not hold any relationships or affiliations with the companies listed above other than my own LinkedIn profile.

Salvador Bentolila, PE, ENV SP is a Civil Engineer, specialized in Water Resources. He currently works as a Water/Wastewater engineer at AECOM and has experience with design and development of water supply, irrigation and wastewater systems.



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Dampness in building, causes of dampness and effect of dampness.


Dampness is the presence of gravitational moisture into the walls, flooring of roofs, one of the basic provision of the building is that should remain dry free from moisture travelling through building parts like a wall.

Dampness is to reduce the strength of building components.

Dampness prevention is the most part of building or structure design,

Every building should be a damp proofing course.

Provision of damp proofing course is to prevent the entry of moisture into the building structure.

Causes of dampness in building

1. Moisture rising up the walls from ground
2. Rains travel from walls tops.
3. Rain beating against external walls.
4. Condensation
5. Miscellaneous causes.

Moisture rising up the walls from ground

The building is constructed in soil. The substructure is into the ground some depth if the soil is previous, moisture constantly travels through if for impervious soil lots of soil present. The moisture is rise through the wall from substructure to superstructure through capillary action. Rise of groundwater is also the reason for moisture rise into the building through wall and floor.

Rains travel from walls tops.

If the wall top is not properly protected with waterproofing course then the water is entering into the wall from the top of the wall go down. Also, the leakage of the roof is the causes of dampness in a building.

Rain beating against external walls.

During the heavy rainfalls sometimes rains beating against the external face of walls and the walls are not properly treated. Then water is entering into the wall this will cause dampness of interior of the building structure. If the balconies do not have sufficient outward slop then the water is entering the walls from walls junction and it will cause the dampness in a building.


Due to condensation of atmospheric moisture, water is deposited on the walls, floor and roof, this will cause dampness in a building.

Miscellaneous causes.

Improper drainage

Improper drainage at the building site may cause dampness. Because deposit of water around the building the water is rise into the walls and floors through the capillary action.

Insufficient roof slope.

 For flat roof should be provided sufficient slope for the drain of rainwater. Otherwise, the rainwater is entering into the roof that will cause dampness.

Rainwater pipes leakage 

Rainwater pipes leakage from defective rainwater drainage pipe may cause dampness in walls.

Imperfect orientation 

Imperfect orientation if the wall does not get proper sunlight and heavy shower may remain damp.

Effect of dampness

1. Travel of moisture through walls and ceiling may cause unlikely patches.

2. Moisture travel may cause suffering and crumble of plaster.

3. The continuous presence of moisture in the walls may cause efflorescence resulting in disintegration of bricks stones tiles etc. and consequent reduction in strength stones tiles etc, and consequent reduction in strength.

4. Moisture cause rusting or corrosion of metal fitting attached with walls, roofs and floorings.

5. Dampness promotes and accelerates the growth of termites.

6. Electrical fittings get worsen gives rise to leakage of electricity and consequent damage of short circuit.

7. The wall decoration is damaged. this is costly to recover.

8. Dampness creates unhealthy living conditions.

9. Floor coverage damaged on the damp floor are cannot use a floor covering

10. The flooring may lessen due to dampness. Because of dampness reduction the adhesion.



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Top Five Digital Tools Must Buy Civil Engineers

Hello, Every Civil Engineers Welcome To My Blog. Today I Will Inform You Some Digital Devices For Used In Our Civil Engineering  Field. 

This Is Very Valuable and Make Our Works to Simplify.

Line Laser Level Measure Beam

Line Laser Level Measure Tool Is Produced By Bouch -click here to buy-

Technology Improving Every Day Very Fast This Equipment Is Simplified Some Jobs.

Bouch Laser Line Laser Used For Exterior and Interior Horizontal Leveling  And Vertical Alignment.

It Is Used In All Job site Conditions.

It Gives 360 degree Laser Plane Also 90 Degree Angles.

This Laser Extended In All Light Conditions Up To 15 Meters.

It Also Used Slope Works

It Can Be Used To Following Purposes

1.Laying Tiles In Wall In Any Location With Exact Right Angles Without Using Of Any Other Devices.

2.Laying Cupboards And Shelves.

3.Laying Floor Skirting With Good Alignment.

4.Instilling Electrical Sockets.

5.Mounting Windows and Doors Frames.

6.Mounting Windows and Doors Frames.

7.Fixing Hand Rails In Staircase With Good Angle.

Laser Distance Measuring Meter (Leica Disto X3 Laser Distance Meter )

This Device Is Used To Measure The Distance between The Objects With The Help Of Laser Dot.
You Have To Measure From A Very Narrow Profile Notches, Corners.
You Can Also Measure the Diagonal.-click here to buy-

Laser Line Sprit Level

This Is Very Attractive Tool, It Can Be Used For Every One Like Engineers, Mason, carpenters  Etc.

This Tool Is Used To Check The Sprit Level Of Any Surface, Also For In Knight Time. It Has Inbuilt Led.-click here to buy-
This Device Also Have Inbuilt Of Measuring Tape And Horizontal As Well As Vertical Laser Lines
 For Accurate Measurement.

You Can Fix The Parallel Point Of Any Compared Surfaces With The Help Of Laser Line Points.

Digital Angle Finder

Digital Angle Finder Is Very Cheap And Efficient Tool.-click here to buy-

That Can Be Used To Set Angle Of Any Object Like You Can Mark The Line Of A Wall In Any Angle.

It Is Must Used For All Architects And Masons For Mark The Angle For Any Architect  Works.

Mini Bubble Sprit Level.

This Is The Very Small And Efficient Tool, It Can Be Carry With In Pocket Of All The Times
This Small Bubble Tube Is Used To Check The Surface Alignments, Door Alignment, Window Alignment -click here to buy-


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Access Panels For Winter - A Builders Guide

Building Talk – Prepping for Winter

Did you know that when it comes to winter, ensuring your building and your projects are ready for what may come is essential? It is essential in ensuring the protection of exposed openings and wirings but also, it is essential in ensuring that any work that has stopped due to winter is not affected with the sometimes-harsh cold temperatures and elements that do come with winter. When it comes to winter, access panels can be both a blessing and a curse – which is why ensuring that when it comes to prepping for winter all scenarios and options are considered and thought out because not prepping for winter can cause both project delays and budget issues.

Sealed and coated

Access panels come in a variety of materials, but more importantly, they can come with various coatings as well to enhance its functionality and resistance to its surrounding environment. When it comes to prepping for winter and access panels – a contractor knows the importance of ensuring that access panels installed in the exterior need to be not only coated accordingly but the ideal material to withstand the possible drop in temperatures. Why is this important? If access panels are installed in areas that have not been properly insulated or they are a temporary solution, not ensuring the proper sealing and coating can result in exposure to the elements which can affect the overall project. Not only can it affect the overall project but it can create a draft and depend on where it is located in the building and room – this can lead to increased heating bills.
Ensuring a proper seal and coating upon insulation can ensure that your space and area is truly prepared for the elements of winter. Whether the coat is an extra layer of water resistant or possibly a coating of insulation between the panes of the panel – preparing for winter means considering the panel used for the project.

Timing is everything

Depending on the location of a project – timing can mean being prepared for winter and not. When it comes to preparing for winter, contractors and builders understand how important it is to ensure that they don’t leave things to the very last minute. For example, contractors would avoid leaving the rust proofing of their machinery, tools and gates before the weather became too cold and unbearable; however, if they leave it to the last minute this can result in struggling to get it done in the conditions of the winter weather. Timing with preparing for winter offers many benefits but more importantly, it ensures that nothing about the building or project space is jeopardized. Winter can bring with it frigid temperatures but it can also bring ample amounts of snow which can cause damage to places and tools that are not winter-proofed.

While some project leads and contractors think that they can beat winter or that they have ample time to prep for winter the reality is that in some regions and cities, winter can come unexpectedly but also early. For projects that began as something from the ground up – it’s important that whatever parts are exposed to the elements are winterized to the best of their abilities. Whether that is using tarp or pushing through to ensure that all necessary covering struggles are built to protect against the elements, specifically the snow.

Winter prepping the key to building success

Did you know that when it comes to the construction and building industry – winter is one of the greatest obstacles experienced by project managers and contractors. A seasoned contractor understands that the success of a project sometimes means weathering through the seasons and the elements. Winter is one of the hardest seasons to work through but also to ensure that a project does not veer off course. Prepping for winter is a contractor attempt to ensure that this does not happen but also that their work is not delayed or affected by the harsh conditions and elements.

Whether its access panels, windows, roofs or flooring – indoor or outdoor, preparing for winter will be not only a great time investment but monetary one as well. Just as one prepares for the laying of foundation or dry walling – preparation for the change in seasons is important too and sometimes underestimated. Don’t find yourself chilled by a draft or buried in snow – it’s important to consider preparation all year round, rain, sun and snow.



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How To Calculate Reinforcement In Circular Slab

We Already Discussed How To Prepare Bar bending Schedule For Rectangular And Square Shape Slab. Now We Are Going To Learn How To Calculate Reinforcement For Circular Slab.

In Circular Slab Reinforcement Length Is Changed Due To Spacing Of The Reinforcement.

For This Cause Using Pythagoras Theorem To Find Out The Length Of Each Reinforcement.

L= Diameter Of Slab – Nominal Cover
For Pythagoras Theorem L1= (R2 – H12)2    H1, H2, H3 =Spacing Of Reinforcement
                                             L2= (R2 – H22)2    R =  Radius Of Slab ( Excluding Nominal Slab )

Same Steps For Other Reinforcements

Example For Circular Slab Reinforcement Calculation

Find The Reinforcement Details Having The Diameter Of 3 m  Providing Main Reinforcement 10 mm Dia And Distributor 8 mm Dia At Spacing 200 mm And Nominal Cover Is 25 mm

✦ L = 3 – 2 ( 0.05 )
L =2.95 m

 L1 = (R2 – H12) X 2  
 L1 = (1.4752 – 0.22)2    
L1= 2.92 M

 L2= (R2 – H22)2  
L2= (1.4752 – 0.42)2    
L2= 2.84 M

L3= (R2 – H32) X 2
L3= (1.4752 – 0.62) X 2
L3= 2.70 M

 L4 = (R2 – H42) X 2
L4 = (1.4752 – 0.82) X 2
L4 = 2.48 M

 L5 = (1.4752 – 12) X 2
L5 = 2.16 M

 L6 = (R2 – H62) X 2
L6 = (1.4752 – 1.22) X 2
L6 = 1.72 M

 L7 = (R2 – H72) X 2
L7 = (1.4752 – 1.42) X 2
L7 = 0.93 M

Total Length Of Main And Distribution Reinforcements

= L + 2(L1)+ 2(L2)+ 2(L3)+ 2(L4)+ 2(L5)+ 2(L6)+ 2(L7)
= 2.95 + 2(2.92) + 2(2.84)+ 2(2.70)+ 2(2.48)+ 2(2.16)+ 2(1.72)+ 2(0.93)
= 34.45 M

Total Weight Of 10 Mm Dia Main Reinforcement

Weight Of 10 Mm Bar Per Metre Length = 0.617 Kg /M
Weight = 34.45 X 0.617
           = 21.26 Kg

Total Weight Of 8 Mm Dia Main Reinforcement

Weight Of 8 Mm Bar Per Metre Length = 0.395 Kg /M
Weight = 34.45 X 0.395
           = 13.60 Kg

Total Weight Of Reinforcement For This Slab = 21.26 + 13.60
          =34.88 Kg



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Compaction Of Concrete And Methods Of Compaction Of Concrete


Compaction is  one of the process of concreting. Compaction is the process of exhaust of air voids from the concrete. Because the presence of air voids make honeycomb in concrete. It will total make the concrete strength less. 1 % of air voids reduce the concrete strength approximately 6 %.

 Compaction of concrete can be done either by manually of mechanically. Manual compaction is the hand compaction without use any machines just it is done by using tamping rods. 

 Mechanical compaction in term machines is used to make compaction they are vibrators. 

 The compaction process is explained below deeply.


 They are many factors consider for choosing compaction method such as reinforcement quantity and spacing, depth of concrete structure, nature of availability of machines, location of concrete structure, concrete paste consistency ,form work difficulty. Methods of compaction are below.


 Hand compaction is done by three methods Roding, ramming and tamping.

 In Roding method a 2 m long and 16 mm dia rod is used. The edges of the rod should be sharp. Thickness of concrete is 150 mm to 120 mm this method is followed

 Compaction process is done throughout the concrete area.  Compaction should be proceeding until it is get fully compacted.

 Another method is tamping. In tamping method 10 cm x 10 cm size cross beam is used to compact the concrete. Compaction and concrete surface level is maintained uniformly. it is used for road pavement flooring concrete and roof concrete works.


 In mechanical compaction method vibration technique is mostly used. Vibration causes temporary liquefaction so the stored air between aggregates is removed immediately. Various types of vibrators are used. They are following below.


 Internal vibrators or needle vibrators are used for compaction of slabs , beams, columns . Vibrator needle head is having diameter of 2 cm to 18 cm and the shape of the head is cylindrical. Internal vibration is maintained accurately because over vibration time make the concrete segregation. Vibrator needle should be submerged into concrete element.


 External vibration method is used where internal vibration can’t be used. Because thin concrete layer or heavy reinforcement structure. External vibrators consume more power compared to internal vibrator, also it give less effect. Form work required extra strong for external vibration method.


 This method is used only laboratories. Concrete is placed above table and the vibrator is fixed below table.


 Surface vibrators are fixed a long board, vibrators are activated then the vibration is transferred into concrete surface. This is not effective method. Also this method is normally used where the depth of concrete is 10 to 15 cm like roof slab and floor slab.


 Concrete structure required adequate compaction otherwise the following problems may be arise.


 In adequate compaction or without compaction make honey comb in concrete structure. Honey comb is nothing but air voids between it is after settlement of concrete it is formed pit. It is totally affect concrete strength.


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How To Calculate Volume Of Trapezoidal Footing

Individual Footings Are Mostly Used In Residential Buildings And Small Building. Usually Individual Footing Have The Shape Of Rectangular, Square And Trapezoidal.

Rectangular And Square Shape Footings Are Calculated The Volume By Simple Steps

Volume Of Rectangular Footing = Area ( A x B ) X Height
Volume Of Square Footing = Area ( A2)  X  Height

Also Trapezoidal Footing Volume Calculation is The Easy Process. I Will Explain Broadly About Volume Calculation Of Trapezoidal Footing Below.

V = H / 3 ( A1 + A2 + ( A1 X  A2 )

H = Height Of Trapezoidal Portion
A1 = Area Of Bottom Of Trapezoidal Portion
A2 = Area Of Top Trapezoidal Portion

Example Calculation For Trapezoidal Footing Volume Calculation.

V = H / 3 ( A1 + A2 + ( A1 X  A2 )
Where H= 0.3 M
A1= 1.5 X 1.5 = 2.25 M2
A2= 0.9 X 0.9 = 0.81 M2
V = 0.3/ 3 ( 2.25+ 0.81+ ( 2.25 X  0.81 )
V = 0.1 ( 3.06+ 1.35)
V = 0.441 M3



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Derivation for d2/162

Hello every civil engineers. We know that d2/162  is the formula to find out the weight of circular steel bar per metre length . but some persons don’t know how  is arrived

So I will explain  how this formula is arrived.
Weight of circular shape steel bar per metre length = area x length x unit weight of steel

Unit weight of steel = 7850 kg/m3
Therefore,  weight = πD2/4 x 1000 x ( (7850/1000 x1000 x 1000 ) )
put all the values in ‘mm’
= 0.7854 x D2 x ((7850/1000 x 1000 ))
= D2 x ( ( 6162.25 / 1000 x 1000 ) )
= D2 X 0.006162
= D2 x 1 / (0.006162 )-1
= D2 /162.28
So we take
Weight of steel bar per metre length = D2 /162

Note : why use this step 1 / (0.006162 )-1  . because 0.006162   is equal to 1 / (0.006162 )-1   but 0.006162  is six digit value It is not remember in our mind therefore this step is used for our remembrance. 



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