By Admin on Thu 18 July 2019 in WRAS/Certifications
BS EN 1717:2000 deals with the protection of potable water supplies from pollution caused by back-flow. The standard applies to water installations and connected appliances inside private premises. The standard details the type of protection device (if any), required to be used to prevent back-flow contamination of potable water in accordance with the potential hazard to human health.
Depending on the potential hazard EN 1717 divides flowing liquids into five categories. The higher the danger the higher the category number. The need for, or type of protection device required is determined by the liquids category number.
Category 1 - Covers water intended for human consumption, coming directly from a potable water distribution system. Under the standard water of this category does not require any back-flow protection.
Category 2 - Represents liquids that present no hazard to human health. These liquids are recognised as being fit for human consumption. Category 2 includes water taken from a potable water distribution system, which may have undergone a change in taste, odour, colour or temperature (heating or cooling). Examples of this include water from a drinks dispenser or vending machine. Category 2 liquids require the installation of type EA or EC devices: verifiable single or double non-return check valve.
Category 3 - Represents liquids presenting some hazard to human health due to the presence of one or more harmful substances. Such liquids include water used for bathing or in a heating system. In these situations a directly controlled mechanical dis-connector (Type GA), or a back-flow preventer (Type CA), must be installed.
Category 4 - These liquids present a hazard to human health due to the presence of one or more toxic or very toxic substances, or one or more radioactive, mutagenic or carcinogenic substances. These may include water from industrial, or medical processes or other activities such as cleaning. Here a through-flow controlled mechanical disconnector (Type GP) or a back-flow preventer (Type BA) should be used.
Category 5 - These liquids represent a high risk to human health due to the presence of microbiological or viral elements. Liquids in this highest risk group require an unrestricted air gap exhaust (Type AA or Type AB).
Back-flow Prevention Device Types
The F314 series of flow restrictor cartridges from RPE srl offer suitable protection in situations that include category 2 or category 3 liquids, these typically include applications such as ice making machines, vending machines, carbonated drink dispensing machines, hot and cold water mixing, unpressurised steam ovens and the like. See below chart for comparison protection requirements.
| Example installations | Fluid type | Appropriate back-flow prevention device | Device Type |
|---|---|---|---|
| Ice making machine | Fluid 2 | Verifiable single check valve | EA |
| Carbonated drink dispensing machine | Fluid 3 | Verifiable double check valve | EC |
| Hot and cold water mixing | Fluid 3 | Verifiable double check valve | EC |
| Drinks dispensing equipment, vending machines, coffee machines | Fluid 2 | Verifiable double check valve | EC |