Hydrant pressure is measured by attaching a pressure gauge to one of the hydrant's outlets.
Measuring hydrant pressure is a key process for assessing water supply capabilities, crucial for firefighting and ensuring the overall health of the water distribution system. The primary method involves the use of specialized equipment directly connected to the hydrant.
The most common method, particularly during assessments like flow tests, involves using a pressure gauge.
Here's a breakdown based on standard procedures:
- Equipment: A calibrated pressure gauge is required. These gauges are specifically designed to handle the pressures found in water distribution systems.
- Connection: As described in a typical single hydrant flow test procedure, a pressure gauge is attached to one of the outlets of the hydrant.
- Preparation: Before taking readings, air is often expelled from the hydrant and the connecting hose/fitting to ensure an accurate water pressure reading.
- Taking Readings: Two critical types of pressure readings are commonly taken:
- Static Pressure: A pressure gauge reading is taken before the hydrant is flowed. This represents the pressure in the system when water is not actively flowing from that specific hydrant.
- Residual Pressure: A pressure gauge reading is taken while the hydrant is being flowed (usually from a different outlet on the same or a nearby hydrant). This indicates the remaining pressure in the system when water is actively being demanded.
| Pressure Type | When Measured | What it Represents |
|---|---|---|
| Static | Before water flow starts | System pressure at rest |
| Residual | While water is flowing from outlet | System pressure under flow conditions |
Measuring both static and residual pressure, along with the flow rate, allows technicians and engineers to determine the available water supply and assess system performance.
Understanding these pressure measurements is vital for:
- Determining water availability for firefighting.
- Evaluating the capacity and condition of water mains.
- Planning system improvements or expansions.
In essence, hydrant pressure is typically measured directly at an outlet using a pressure gauge to capture system pressure both before and during water flow.
