Water Supply Industry Interpretations and Advice

  • Area of Interest : Backflow prevention
  • Topic : Risk assessment
  • Title : Laboratories - backflow risk
  • Clause Reference : Regulation 3, Schedule 2 paragraph 15 & G15.3
  • Reference Number : B01
  • Decision Date : October 2000 (Revised July 2016) 

In all premises with a public water supply, every water system must be protected by the provision of adequate backflow protection to prevent backflow of fluid from any appliance, fitting or process from occurring.  In addition to point of use backflow protection, zone protection may also be required.

To determine the level of risk posed, distribution systems serving laboratories must be individually risk assessed by the local water undertaker. Factors taken into consideration when assessing laboratory installations will include, but are not limited to, the type of work undertaken and any equipment and chemicals/materials used in the work of the laboratory.

Taps in laboratories
The risk posed by a tap in a laboratory (including those with a hose attached)discharging into a sink or other receptacle can only be determined following a risk assessment by the local water undertaker. 

In the case of both sinks and other receptacles, appropriate point of use backflow protection is typically provided by an AUK3 tap gap. However, where the tap gap may be compromised an alternative form of backflow protection must be provided. 

The tap gap is considered likely to be compromised where:-

  • The tap is designed to accommodate the attachment of a hose; or
  • The tap is intended to be adapted to accommodate the attachment of a hose: or
  • It is unlikely that the appropriate distance (tap gap) will be maintained between the tap outlet and spill-over level of the sink or other receptacle 

When risk assessing laboratory taps which can accommodate hoses, two separate aspects are considered:

  1. Is it likely that a hose be connected which links the tap to any laboratory equipment? If so what are the risks associated with this equipment?
  2. Does the discharge point of the hose (which includes hoses discharging from laboratory equipment supplied via a laboratory tap) fall below the spill-over level of the sink?

Where an appropriate fluid category 5 tap or air gap cannot be maintained between the hose discharge point and the spill-over level of the sink/ receptacle alternative fluid category 5 backflow protection must be installed upstream of the tap.

Where laboratory equipment, process or experiment has been interposed between the tap outlet and the spill-over level of the sink or other receptacle, even where a fluid category 5 air gap is maintained between the hose discharge point and the spill-over level of the sink or other receptacle, a risk assessment carried out by the local water undertaker will be required to determine the level of risk associated with the equipment, chemicals/materials and/or processes involved.This will determine the appropriate level of backflow protection required upstream of the tap.

In cases where all laboratory taps (at the same level) are supplied from a dedicated storage cistern fed via a fluid category 5 air gap, additional backflow protection may not be required at the laboratory tap(s). Water supplied for domestic use such as hand-washing must not be connected to this type of system. Further advice should be sought from your local water undertaker.