Friction Loss Tutorial Used in conjunction with the Friction Loss Check Sheet and any Irrigation Plan

Some terms and abbreviations gpm = gallons per minute fps = feet per second cu.ft. = cubic feet ft. or ‘ = feet in. or “ = inches Sch = schedule Cl = class PVC = polyvinyl chloride PE = polyethylene

In the beginning... Start with any sprinkler head layout plan

Next... Familiarize yourself with the drawing and the drawing’s legend Use the information in the drawing’s legend to determine the “available flow”

The Legend

Information from the legend Water meter size Static Pressure City water service – pipe size and type Sprinkler heads and nozzles Sprinkler valve sizes and types Drawing scale

Available flow... Is the amount of water available to build the system Building to the available flow insures the system will work It typically insures there will be enough pressure at the last sprinkler head as well Determine the available flow using the three “available flow” rules

Rule #1 – 10% Rule Acceptable pressure loss through a water meter (for irrigation) should not exceed 10% of the minimum static pressure available at the city water service This limit is imposed to prevent further, heavy pressure loss through the system

Rule #1 From the legend: Determine the static pressure: 60 psi Then determine 10% of the static pressure: 6 psi

Rule #1 Using the water meter table and the appropriate size water meter Find the pressure loss of 6 psi on the water meter table If there is no 6 psi in the pressure loss column go to the next lowest reading NEVER go to the next highest reading

Rule #1 6 PSI does not exist in the table under the appropriate meter size of 5/8” Move up to the next lowest psi loss to determine the flow Rule #1 = 12 gpm

Rule #1 Add the flow determined by Rule #1 to the drawing near the legend Rule #1 = 12 gpm

Rule #2 – 75% Rule Maximum safe flow through a water meter (for irrigation) should not exceed 75% of the maximum flow of a water meter

Rule #2 Determine the maximum flow through a water meter Find the correct meter size on the table Match the last pressure loss number to the adjacent flow The maximum flow of a 5/8” meter is 20 gpm

Rule #2 To find rule #2 determine 75% of the maximum flow 75% of 20 gpm = 15 gpm (20 x.75 = 15) Rule #2 = 15 gpm

Rule #2 Add the flow determined by Rule #2 to the drawing near the legend Rule #1 = 12 gpm Rule #2 = 15 gpm

Rule #3 – Safe velocity rule Never exceed 5 fps (feet per second) through plastic pipe (PVC or polyethylene) and... Never exceed 7.5 fps through metal pipe (galvanized steel or copper) Use this rule for both the city water main and job’s water service

Rule #3 Use the appropriate table for the pipe type being used Locate the pipe size on the table Follow the velocity column down to last velocity not exceeding 5 fps for plastic pipe or 7.5 fps for metal pipe Match the velocity to the flow

Rule #3 Refer to the legend The “city main line” is 1” Type K copper pipe

Rule #3 Not exceeding 7.5 fps with copper pipe we have a maximum flow of 18 gpm Rule #3 = 18 gpm

Rule #3 Add the flow determined by Rule #3 to the drawing near the legend Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #3 – 18 gpm

Determine the available flow After resolving the 3 available flow Rules: Determine the “limiting factor” or the rule with the lowest flow. Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #3 = 18 gpm

Determine the available flow Rule #1 has the lowest flow of 12 gpm Rule #1 is the limiting factor Therefore the available flow is determined by Rule #1 The available flow is 12 gpm

Available flow Add the available flow to the drawing below the 3 rules Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #3 – 18 gpm Available Flow = 12 gpm

Next... Label the plan With ALL of the obvious information, including: Flows to each nozzle in the legend – multiplying the flows times the number of nozzles to determine the demand Flows to each nozzle along the pipe runs Flows through each length of pipe

Next... Label the plan Type and size for each piece of pipe Determine the length of each piece of pipe Type and size the main line if given Determine the type and size of the main line if not already given Fill in the valve callout with the appropriate information

Label and add the flows to the nozzles in the legend Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #2 = 18 gpm Available Flow = 12 gpm x 4 = 1.56 gpm x 10 = 7.9 gpm = 9.46 gpm

Label the flows to all the nozzles along the pipe runs Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #2 = 18 gpm Available Flow = 12 gpm x 4 = 1.56 gpm x 10 = 7.9 gpm = 9.46 gpm

Label the flows through each length of pipe Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #2 = 18 gpm Available Flow = 12 gpm x 4 = 1.56 gpm x 10 = 7.9 gpm = 9.46 gpm

Size and type each length of pipe Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #2 = 18 gpm Available Flow = 12 gpm x 4 = 1.56 gpm x 10 = 7.9 gpm = 9.46 gpm

Determine the length of each piece of pipe Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #2 = 18 gpm Available Flow = 12 gpm x 4 = 1.56 gpm x 10 = 7.9 gpm = 9.46 gpm

Size and type the main line Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #2 = 18 gpm Available Flow = 12 gpm x 4 = 1.56 gpm x 10 = 7.9 gpm = 9.46 gpm

Fill in the valve callout with the valve number, valve size and flow through that circuit Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #3 = 18 gpm Available Flow = 12 gpm x 4 = 1.56 gpm x 10 = 7.9 gpm = 9.46 gpm

The next step Using a “friction loss check sheet” determine the available pressure at the last head This tells if the system will work... or not

Filling in the check sheet Referring back to the irrigation plan x 4 = 1.56 gpm x 10 = 7.9 gpm = 9.46 gpm Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #3 = 18 gpm Available Flow = 12 gpm

Filling in the check sheet Fill in the number for the lateral line in question Fill in the actual flow for the lateral line Add the “rounded-up” flow next to the actual flow Also fill in the static pressure found in the legend

gpm 60 psi

City main line losses Refer to the plan, fill in the information for the city main line: Main line size and type, pressure (friction) loss per 100 feet, length of the main line converted to a decimal (divide the length by 100) The friction loss in the main line

City main line losses The loss per 100’ of 1” K-Type copper pipe is 3.53 psi/100’

gpm 60 psi 1” Type K Copper 3.53 psi 15’ (.15) 0.53 psi Loss/100’ x Length = Loss

Change in elevation losses (*or gains) Fill in the elevation change for the city main line Multiply the change in elevation times.433 to determine the pressure loss caused by the elevation change *If the water meter is above the level of the valve there will be a gain in pressure

gpm 60 psi 1” Type K Copper 3.53 psi 65’ (.65) 2.29 psi Loss/100’ x Length = Loss 8’3.46 psi

Water meter losses Fill in the water meter size Refer to the water meter table to determine the friction loss for the flow being used Add the city main line losses for the total city main line losses

gpm 60 psi 1” Type K Copper 3.53 psi 65’ (.65) 0.53 psi Loss/100’ x Length = Loss 8’3.46 psi 1.6 psi 3/4” 5.59 psi

Back flow and shut-off valves When applicable list the necessary information for the backflow and shut-off valves found in the appropriate catalogs and tables

gpm 60 psi 1” Type K Copper 3.53 psi 65’ (.65) 0.53psi Loss/100’ x Length = Loss 8’3.46 psi 1.6 psi 3/4” 5.59 psi N/A

Referring back to the irrigation plan x 4 = 1.56 gpm x 10 = 7.9 gpm = 9.46 gpm Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #3 = 18 gpm Available Flow = 12 gpm

gpm 60 1” Type K Copper 3.53 psi 65’ (.65) 0.53psi Loss/100’ x Length = Loss 8’3.46 psi 1.6 psi 3/4” 5.59 psi N/A

Service line losses Referring back to the plan: Input all of the necessary information for the service line losses (from the meter to the irrigation valve) List each section of service line involved – line type, line size, flow, flow rounded up, length of pipe, length of pipe converted to a decimal

Referring back to the irrigation plan x 4 = 1.56 gpm x 10 = 7.9 gpm = 9.46 gpm Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #3 = 18 gpm Available Flow = 12 gpm

Service line losses For this example use the pipe tables for Schedule 40 PVC Determine the loss per 100’ for (in this case) the 1” SCH 40 PVC service line at the flow of 10 gpm The pressure loss is 2.40 psi/100’

gpm 60 1” Type K Copper 3.53 psi 65’ (.65) 0.53 psi Loss/100’ x Length = Loss 8’3.46 psi 1.6 psi 3/4” 5.59psi N/A SCH 40 1” 9.4 gpm 10 gpm 2.40 psi 65’ psi Loss/100’ x Length (in decimal) = Friction Loss

Service line losses Add the losses for each section of pipe(s) for the piping loss Add 20% for fitting losses Add the piping loss plus the 20% to determine the total service line loss

gpm 60 1” Type K Copper 3.53 psi 65’ (.65) 0.53 psi Loss/100’ x Length = Loss 8’3.46 psi 1.6 psi 3/4” 5.59psi N/A SCH 40 1” 9.4 gpm 10 gpm 2.40 psi 65’ psi Loss/100’ x Length (in decimal) = Friction Loss 1.56 psi.31 psi 1.87 psi Fitting Loss = Piping loss x 0.2

Irrigation valve losses Referring back to the plan: Input the irrigation valve size Enter the friction loss for the correct size irrigation valve found in the appropriate parts catalog

1.87 psi.31 psi 1.56 psi Friction Loss = Piping loss x 0.2 3/4” Rainbird ASVF 4.6 psi

Lateral line losses Referring back to the plan Start at the farthest sprinkler head from the valve List each section of lateral pipe working from the farthest head back to the valve List pipe types, sizes, flows, flows rounded up and lengths

x 4 = 1.56 gpm x 10 = 7.9 gpm = 9.46 gpm Rule #1 = 12 gpm Rule #2 = 15 gpm Rule #3 = 18 gpm Available Flow = 12 gpm

1.87 psi.31 psi 1.56 psi Friction Loss = Piping loss x 0.2 3/4” Rainbird ASVF 4.6 psi Cl 315 Cl 200 1/2” 3/4”.39 gpm 1.18 gpm 1.97 gpm 2.76 gpm 3.55 gpm 4.34 gpm 4.73 gpm 9.4 gpm 1 gpm 2 gpm 3 gpm 4 gpm 5 gpm 10 gpm 9.5’ 45.5’

Lateral line losses Refer to the appropriate pipe tables to determine the lateral line losses In this case: Class 315 PVC for all of the 1/2” PVC and Class 200 for the 3/4” PVC

Lateral line losses Input the lateral line losses per 100’ Multiply the losses per 100’ x the decimal length of each section of pipe to determine the losses for each section of pipe Add the losses and include the fitting losses for the total lateral line loss

1.87 psi.31 psi 1.56 psi Friction Loss = Piping loss x 0.2 3/4” Rainbird ASVF 4.6 psi Cl 315 Cl 200 1/2” 3/4”.39 gpm 1.18 gpm 1.97 gpm 2.76 gpm 3.55 gpm 4.34 gpm 4.73 gpm 9.4 gpm 1 gpm 2 gpm 3 gpm 4 gpm 5 gpm 10 gpm 9.5’ 45.5’ psi.78 psi 1.65 psi 2.82 psi 4.26 psi 4.31 psi 1.96 psi.40 psi.27 psi.16 psi.07 psi.02 psi 4.02 psi.67 psi 3.35 psi Fitting Loss = Piping loss x 0.2

Total of all friction losses Add all of the accumulated friction loss totals from above, including: Total city main line losses Back flow device loss Shut-off valve loss Service line loss Irrigation valve loss And lateral line losses

1 9.4 gpm = 10 gpm 60 psi 5.59 psi N/A 1.87 psi 4.6 psi 4.02 psi Add the losses for a total of all friction losses: = psi psi N/A

Will the system work? Determine the available pressure at the last head Subtract the total of all friction losses from the static pressure Static pressure - Total of all friction losses = Available pressure at the last head

1 9.4 gpm = 10 gpm 60 psi 7.35 psi N/A 1.87 psi 4.6 psi 4.02 psi Available pressure at the last head = Static pressure – Total of all friction losses 60 psi – psi = psi psi N/A psi Available pressure at the last head = Static pressure – Total of all friction losses

Will the system work? Static pressure - Total of all friction losses = Available pressure at the last head 60 psi – psi = psi The sprinklers require 30 psi to work as the system was designed

Will the system work? The sprinklers require 30 psi to work as the system was designed We have 44 psi (43.93 psi) remaining The system should work Congratulations!