Chapter 2 of 59% of exam

Installation of Underground Fire Main Systems

CSLB weights Underground Fire Main Systems at about 9% of the C-16 exam: trenching and shoring, pipes and thrust blocks, hydrants and fire department connections. This page is a short survey; the PrepPass C-16 Fire Protection study guide teaches the section with worked examples, chapter quizzes and a full practice exam at CSLB's weights.

Trench and shore safely

Five feet is the permit and protective-system depth; four feet is the egress and atmosphere-test depth. Soil is classified as stable rock, Type A, B or C.

Permit
Trenches 5 feet or deeper into which a person must descend need a permit.
Title 8 section 341
Maximum slopes
Stable rock vertical; Type A 3/4:1; Type B 1:1; Type C 1-1/2:1.
Title 8 section 1541.1 Appendix B

Lay pipe and block the fittings

Thrust blocks bear on undisturbed earth and are inspected before the pour. The main is hydrostatically tested and flushed before it is connected to the overhead system.

Underground test
200 psi or 50 psi above static pressure, whichever is greater, for 2 hours.
Moreno Valley Fire Department guideline
Flush
At least 10 feet per second; 880, 1,560, 2,440 and 3,520 gpm for 6, 8, 10 and 12 inch pipe.
Idaho State Fire Marshal acceptance checklist

Set hydrants and connections

A hydrant keeps a 3-foot clear space and impact protection; an FDC is signed, capped and set 18 to 48 inches above grade.

Hydrant clearance
A 3-foot clear space around the circumference of a hydrant.
2025 CFC 507.5.5
FDC sign
Raised letters at least 1 inch high naming the system.
2025 CFC 912.5

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