Preventing contaminated backflow with RPZs

20th June 2016

The Water Supply (Water Fittings) Regulations and Scottish Water Byelaws require domestic water supplies to be adequately protected from backflow. Where equipment is used with fluids or materials which could contaminate, measures to stop harmful substances getting into other parts of the system must be in place.

Preventing backflow can be particularly important in cities, such as London, where the mains cold water pressure can fluctuate, leading to dangerous situations where contaminants are inadvertently allowed to enter into drinking water services. Not preventing backflow is a criminal offence.

For water systems were contaminated with harmful substances may be present, a Reduced Pressure Zone (RPZ) valve or break cistern incorporating a Type AF air gap is required.

How is backflow caused?

Backflow is caused in the following ways:

  1. Fluctuations in water pressure can cause a lowering, and in some cases, a negative pressure or vacuum to occur in the water supply. This may result in fluids upstream being syphoned or sucked, back into other parts of the system. The fluctuations can occur when carrying out repairs or where there is high usage on the system.
  2. Where the pressure in the system downstream is greater than those upstream, fluids can be forced back towards the source into other parts of the system.

Once fluids are in a water system they can be re-distributed to other parts and in some circumstances back into the public mains.

Preventing backflow with Guardian

Guardian Water Treatment’s trained operatives are authorised to carry out both service and replacement of backflow prevention valves, or reduced pressure zone valves, commonly known as RPZ Valves.

Once installed, RPZ maintenance is essential – it is a requirement of the Water Supply Regulations that RPZ valves are annually checked by an approved tester in line with section 7.2 of WRAS AIM 08-01. On completion a copy of the test certificate should be sent to the relevant water authority regulations department for their records.

If an RPZ valve fails the test it must be repaired and retested within a 72 hour period, and where this is not possible the local water authority must be contacted and advised. It can sometimes be necessary to temporarily provide alternative backflow prevention measures depending upon the type of system being served and the assessment of risk.

Prevent contamination and fines, contact us to find out more about our RPZ installation and testing services. Contact us.