Technical investigation for underground fire mains
Underground Fire Hydrant & Fire Main Leak Detection
Frequent jockey-pump cycling, unexplained pressure loss or a failed pressure-holding test may indicate leakage in an underground fire-main system. Before selecting a method, we review how the system is arranged and how it behaves.
Common reasons for an investigation
- The jockey pump starts more often than expected.
- Pressure falls when the system should remain stable.
- A pressure-holding test fails without a visible leak.
- An underground fire-main route is suspected of leaking.
- The excavation area needs to be narrowed before repair work begins.
Information to Send Us
- Total pipeline length
- Pipe material and diameter
- Estimated burial depth
- Current route drawing, branches, hydrants and valves
- Water source and normal operating pressure
- Whether the supply is directly connected to the water authority or supplied through a storage tank and pump system
- Pressure-drop range and how long the drop takes
- Jockey-pump start and stop behaviour
- Jockey-pump cycling frequency
- Available sectional valves and isolation options
- Site noise, access, shutdown and safety requirements
“Not sure” is acceptable for technical details that are genuinely unavailable. The information provided helps us decide what should be checked on site.
How We Check the Pipes
Acoustic ground listening and contact listening can be used to compare suitable points along a pressurised fire main. Wireless noise correlation may help where the route, pipe data and accessible contact points support it.
Nitrogen-assisted testing may be considered only when suitable for the system and separately agreed. It requires proper isolation, safety planning and approval; it is not used on every job.
How the work progresses
- Review the fire-main system — Check the route, branches, valves, hydrants, pumps and test history.
- Understand the pressure and pump behaviour — Review pressure loss, test records and jockey-pump cycling.
- Plan access and safety — Confirm isolation, shutdown, permits and suitable inspection periods.
- Compare sections and accessible test points — Use suitable acoustic or correlation checks along accessible parts of the system to narrow the priority area.
- Mark and explain — Mark the suspected location or zone and explain the recommended excavation or follow-up work.
Understanding water loss
Where reliable meter, flow or pump-performance data is available, the apparent water loss may be estimated in m³/day, m³/hour or L/min. Pressure-drop and jockey-pump cycling records can also help us assess the severity and behaviour of the suspected leak. These figures do not identify the underground leak location by themselves.
What You Receive
- A marked suspected location or investigation zone
- A technical explanation of the observations and limitations
- Inspection photographs and a report when included in the quotation
- Recommendations for excavation, repair or further inspection
After marking
This is a leak investigation, not a certification of the whole fire-protection system. Your appointed contractor confirms the defect after exposing the pipe and carries out the repair.
System evidence
Pressure loss and pump cycling are symptoms to investigate
They do not by themselves prove that one specific buried pipe location has failed. Findings from suitable hydrants, valves and other test points must be compared before an area is recommended for excavation.
Fire-system valves, pump shutdowns and isolation must be handled by authorised site staff under the agreed safety arrangements. Do not shut down or adjust the fire system without authorisation.
Send us the fire-main details.
Send the route drawing, pipe length, material, size and depth where known. Include the water source, normal pressure, pressure-drop records and how often the jockey pump starts.