FDT Event Duration Monitoring for CSO Overflows

Radio Data Networks Deliver Affordable 2-Minute EDM for CSO Overflows with 5-Year Failure Free Service History and Real-Time Spill Mitigation Controls


It may sound incredible but the Radio Data Networks FDT (Flow Detection Transducer) has now been in service for over 5-years without a single reported issue due to battery failure or moisture ingress. However, as others now struggle to get their systems to respond at 2-minute intervals many are not aware that the FDTs actually detect and report flow at an astonishing rate of 2.5-seconds, meaning that no intervention whatsoever is required in the chamber and there is no impact on the FDTs typical 10-year battery life to achieve compliance with the new Environment Agency’s 2-minute reporting requirements at Combined Sewer Overflows for EDM (Event Duration Monitoring).

In practice actual reporting rate of the FDT is set by the above ground collection/logging device, the choice of which as grown enormously since 2012. The original system and by far still the most popular, utilises a battery powered “Booster“, a small wireless repeater box attached to a lamp post to relay the status of a FDT back to telemetry or SCADA, using an Ofcom licenced data channel where it operates a simple relay contact proportional to the duration of the event.

Now in 2017, we offer a wide range of solutions that include use of the Tetra data channels, LAN and also the Iridium Satellite network permitting an FDT to be installed virtually anywhere on the planet! Data can also now be delivered in a wide variety of formats from SDS Tetra Messages, SBD satellite packets, IP packets, e-mails to files in JSON, CSV, XML and the aforementioned volt-free relay contacts.


Comparison Table:

FDT vs GSM/GPRS + Ultrasonic Combination: Typical Performance

Parameter FDT GSM/GPRS + Ultrasonic Head Notes:
Sampling Rate

2-Minute EDM Compatible


2.5 seconds

Yes with limitations

2 or 15-min

The FDT reporting rate is set by the associated Booster or Gateway
Health Message Yes No Every 4-minutes
Deployment Depth 4m and 10m 3m
Real-Time Data & Control Yes No Direct Link to Pumps and valve Controls
Battery life 7-10 years 6-16mths
IP68 + 100% Potted Design for Constant Submersion Yes Partial
Field Programming Not Required Yes FDT Trigger set by cable ties
Confined Space Entry Not Normally Required Yes FDT Normally installed from the surface – no brackets required
Visual Verifiable Trigger Point Yes No FDT is easy to align with spill channel
Live Drive-By Status Report to Vehicle Yes No
Location Function Yes No
SIM Card Required No Yes
Impact protection IK07 ?
Communication Options Licenced Radio

Tetra / DMR


100% Cyber Secure Internet Free Options


No – Requires GPRS/ 3G IP Backbone

Relay Option to existing Outstation and SCADA


CSO Containment valve

CSO Containment valve

The last option, that of relay contact is the most powerful of the FDT’s delivery modes. The local relay contacts aside from providing a totally cyber secure interface to telemetry and SCADA have already been used in anger to instigate a number of local mitigation strategies from switching off pumps that may be feeding the CSO to closing valves at the outlet in dry weather.

In Summary, the FDT is an ideal, high reliability, low maintenance; low TOTEX solution for 2-minute EDM with a proven track record and that has won multiple awards for its ease of use, testability and ability to integrate with existing systems. Further, as the cellular industry migrates fist to 4G and then 5G by 2021, the FDT with it SIM free operation also offers the assurance of operation well into the next decade.

Finally, existing FDT deployments can be upgraded to 2-minute reporting without the need to access the installed device as the only alteration required is the reporting rate of the above ground mounted collection device typically a “Booster”.

Press Office

Radio Data Networks Limited October 2017