STS prepaid meters

A prepaid meter consists of a water meter and electronic latching valve that is connected to a prepaid water controller and neatly packed in a wall mount or above ground box. Waterwatch uses the Honeywell Kent meters for this purpose.

The Prepaid Water Controller (PWC) is an intelligent controller that manages the delivering of prepaid water to residential or commercial installations. The controller is designed to fit into a variety of above–ground or wall-mount meter boxes, compatible with any water meter that facilitates a metrological output pulse. A pulse is generated according to the volume of water consumed that is interpreted by the PWC and that will operate the latching water valve to open or close the water supply through the meter according to the credit status.
Mounted inside the consumer’s house is a remote wall-mount Keypad or Consumer Interface Unit (CIU) that links up with the PWC on the meter box outside, via RF communications link – no additional cables or electricity is required. The CIU indicates the available credit on the meter, and is also used to enter the 20 digit credit tokens bought by the consumer. The CIU refreshes itself automatically every hour, or on demand. A series of user commands are available, to view credit history, water usage as well as many other user-friendly features.

The PWC uses the Standard Transfer Specification (STS) as the credit transfer technology for the loading of purchased credit. Credit tokens are purchased from any participating STS compliant vending platform available at local retailers, ATM’s, the Internet or via SMS. Thousands of STS compliant vending platforms are already established globally for the selling of prepaid electricity and water.

A Credit Token consists of 20 numeric digits, printed on a receipt or voucher and loaded using the CIU keypad. Credit is transferred in units of Litres, and not a monetary value. Units are transferred in multiples of 100L. The token is either printed on paper, or transferred electronically for example per SMS, grouped into 5 blocks of 4 digits each. For example: 3726 4859 5483 4837 1930

The CIU is used to enter the tokens, and forward it to the controller. The token is entered and displayed in the same block format as printed on the token voucher. Once the token is decrypted and validated, the meter credit register is updated, with a response message sent to the CIU, indicating the credit value of the token loaded. A few seconds later the CIU automatically refreshes itself with the new credit value.

Due to the open specification nature of STS, third party vending infrastructure is already established and operating in about 180 countries, including Southern Africa. These Vending Systems all conforms to the same IEC specification and are approved by the STSA.


  • Above Ground box or Wall mount box installation
  • Consumer Lock to shut off water supply on demand
  • Leak detection and minimum flow measurement
  • AMR (Automated Meter Reading) with no duplications
  • Valve with 15 Bar maximum pressure rating
  • Water Conservation Limit per day to limit loss due to pipe bursts etc.
  • Credit low indication on CIU
  • Resettable user totalizer for checking different consumption patterns such as washing machine consumption
  • Consumption History - Consumption data logger for 90 days on CIU and 12 months on PWC
  • Automated meter configuration by the Utility – no need to visit each meter
  • Token History - The PWC stores the last 10 tokens entered
  • Credit use History – The PWC stores the monthly total Paid Credit used over the last 12 months


STS (Standard Transfer Specification)
The PWC is certified for compliancy to IEC62055-41 & IEC62055-51 standards
Certificate Nr.: STS544

NRCS(National Regulator for Compulsory Specifications)
The system is approved to SANS1529-1:2006 and SANS1529-9:2008.

ICASA (Independent Communications Authority of South Africa)
The RF Radio equipment is registered and approved to EN 300 220, EN 301 489-1&3 and EN 60950