Online Pressure Monitoring for Fire and Water Networks: Points, Communications, Selection and Acceptance

For online pressure monitoring in fire and water networks, check points, power and communications, sensors, platform alarms and acceptance in order. Trend monitoring and water-hammer capture require different sampling strategies. This article supports equipment and system selection; required monitoring functions remain subject to project design and applicable requirements.

Step 1: Choosing monitoring points

Point type	Purpose	Placement guidance
Hydrant / network extremity	Confirm pressure at the most unfavourable point	Network extremities and top-floor outlets
Pump room outlet	Capture water hammer and fluctuation from pump starts	Straight run at the pump outlet, away from elbows
Around pressure-reducing valves	Detect valve failure	One point before and one after, for comparison
Zone boundaries	Locate leakage sections and abnormal pressure drops	Paired points at each zone inlet and outlet
Elevated tanks and reservoirs	Combine level and pressure judgement	Used alongside a level transmitter

Paired points help compare pressure, but two readings alone do not uniquely locate leakage or blockage. Combine them with flow, valve state, topology and synchronised timestamps. Select points against the project design and site validation.

Step 2: Power and communications

Site condition	Recommended approach	Notes
Mains power and wired network	Mains plus wired uplink	Simplest option; sampling rate can be high
Mains, no network	Mains plus wireless terminal	Prefer external supply with battery backup
No mains, coverage available	Battery plus wireless terminal	Rely on low-power design for service life
No mains, no coverage	Resolve power/coverage; select alternatives under project requirements	Manual inspection does not automatically replace required online monitoring

Design sampling and transmission separately. PM350-RTU standard acquisition is 6 seconds to 5 minutes, with transmission at 10 minutes to 24 hours, suitable for trends. This does not establish millisecond water-hammer recording; confirm effective sampling, triggers and buffering if needed. Include supply, battery version and external loads in the budget; the five-year description is not a project life guarantee.

Choose NB-IoT or 4G by the terminal configuration and measured coverage at the actual point; do not assume automatic dual-network fallback. Retransmission is limited by retention. Test buffer capacity, retention, recovery completeness and alarm delay; deep chambers and metal covers can alter radio conditions.

Step 3: Sensor selection

Need	Recommendation	Key parameters
Local reading for patrols	RS WA30 outdoor display transmitter	Check pressure reference, measuring range and IP configuration; range-specific overload; response as fast as 0.5 ms
Remote reporting, unattended	RS PM350-RTU wireless terminal	NB-IoT / 4G; configuration-specific IP; independently set acquisition and transmission
Level and pressure combined	RS PMLG150 level transmitter	Confirm actual product and project requirements

Size the range from project design pressure and measured transients, covering required peaks while meeting the error target. One-third to two-thirds full scale is only an initial heuristic; there is no single working pressure for every fire or water network. Check overload, repeated pulses and snubbing separately.

First establish whether measurement must reference local atmospheric pressure, then specify ingress protection. Do not substitute sealed gauge or absolute merely to obtain IP68. For possible immersion, confirm venting, connector, permitted depth and duration and test the complete assembly.

Step 4: Data and alarms

1. Sampling: define trend and transient requirements separately. Millisecond water hammer needs suitable bandwidth, effective sampling and validated triggering/buffering, not second-level intervals.
2. Alarm thresholds: define low pressure, high pressure and offline rules for the project. Offline status may involve power, coverage, platform or device faults; it does not uniquely identify removal or flooding.
3. Delivery: configure supported notification channels, recipients, acknowledgement and escalation. Test delivery and delay; do not assume every platform supports SMS or app notifications.
4. Retention: set the period by project and applicable requirements, distinguishing terminal buffering from platform storage. Test outage retention, retransmission, backup and historical retrieval.
5. Remote configuration — prefer terminals whose sampling and transmission settings can be changed remotely, avoiding a site visit for every adjustment.

Beyond its own pressure and temperature channels, the RS PM350-RTU can acquire external signals (multiple pulse inputs, analog, I2C and 485), so one terminal can also carry a flow meter or a third-party instrument, reducing duplicated installation and connectivity costs.

Step 5: Acceptance criteria

Criterion	How to write it
Pressure error	Specify temperature, configuration, allowable error and test method; typical is not a per-unit limit
Ingress protection	Name the IP rating for the specific pressure type and connector
Overload capability	State range-specific ratings and actual dynamic-pulse validation separately
Online rate	Monthly online rate at or above a stated percentage, with a cap on outage count
Data completeness	Whether buffered retransmission succeeded; cap on missing data points
Battery life	For battery points, state expected service years and a replacement plan

Acceptance must not say only “0.5% accuracy” or turn a typical value into a per-unit limit. PM350-RTU lists TEB ≤±0.50 % FS at -20 to 85 °C and 1–100 m altitude. Also agree configuration, test points, reference equipment and allowable error; other conditions need separate confirmation.

Next step

Pilot representative points to validate coverage, data completeness, alarms and maintenance, then roll out to the project schedule. Continue seasonal monitoring, but do not postpone required monitoring or acceptance while waiting for a full season. Fire-system obligations and local requirements must be met separately.

More answers in the FAQ.

Related documentation: downloads page

Specifications: View PM350-RTU datasheet (PDF) · Download PDF · View WA30 datasheet (PDF) · Download PDF