Dynamic Pressure Loss Worksheet

An interactive tool to determine the dynamic pressure at the "worst-case sprinkler" in a sample irrigation system.

Reference Answers (Diagram 1)

Determine the dynamic pressure at the "worst-case sprinkler" using the diagrams below. Note: Two diagrams are used to reduce crowding.

Diagram 1

Determine the dynamic pressure at the "worst-case sprinkler" using the diagrams below. Note: Two diagrams are used to reduce crowding.

= Hunter "PS" Type - Model 15A, Full Circle, 4.0 GPM at 35 PSI

= Control Valve

= Lateral Lines: 1/2" Class 315 PVC, 3/4" & 1" Class 200 PVC

= Main Line Pipe

Initial Pressure at Valve:

35 PSI

Diagram 1: Pipe Sizes

Diagram 2: GPM & Head Spacing

Friction Loss Worksheet

Carry over selections (Type, Size, GPM) when adding new section

Auto-Calculate PSI Loss

Section	Type	Size	GPM/Flow	Length	PSI Loss / 100	PSI Loss this item

		Total PSI Loss in Pipes:

Estimated pressure loss in fittings (10%)

Calculation Reference

These are calculations you must learn and memorize for accurate friction loss estimation. You will be doing these calculations frequently on your Exam.

1. Section PSI Loss

Formula: Length ÷ 100 × Chart_Value

Calculator Tip: Convert feet to decimal factor first. For 150', enter 150 ÷ 100 = 1.5. Then multiply 1.5 × Loss/100.

2. Fitting Loss (10%)

Formula: Total_Pipe_Loss × 0.10

Calculator Tip: Sum all your individual pipe section losses (the result in the table footer). Leave that number on your screen and hit × .1 to find fitting loss.

3. Remaining Pressure

Formula: Start_PSI - Pipe_Loss - Fit_Loss

Total PSI loss in pipe from the valve to the last head:
Pressure at the valve discharge:
Estimated pressure loss in fittings (10% of pipe loss):
Pressure loss in pipe from valve to last head:
Pressure remaining at the last head: