Specific Installation Guidance

Backflow Protection

Laboratories

Laboratories and similar scientific facilities are considered to be a fluid category 5 risk, requiring fluid category 5 backflow protection.

In addition to point of use backflow protection, zone and wholesite protection may also be required.

Taps in laboratories

Point of use backflow protection can be provided in various ways including:

T​ype AUK3 tap gap:

A Type AUK3 tap gap may be accepted as point of use backflow protection. Unless it is considered the tap gap may be compromised, where this is the case 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?

If laboratory taps can accommodate hoses, two separate aspects are considered:

1. Is it likely that a hose will be used to connect 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 or receptacle?

Where a Type AUK3 tap 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.

Alternative backflow protection will be required where laboratory equipment, process or experiment is directly connected to the tap, even if a Type AUK3 tap gap can be maintained between the final discharge point and spillover level.  The level of backflow protection will be determined by the level of risk associated with the equipment, chemicals/materials and/or processes involved. 

T​ype DC arrangement:

A Type DC arrangement installed on a laboratory tap may be accepted as a means of point-of use fluid category 5 backflow protection providing:

The outlet, including the outlet of any hose attached: -

• Remains unrestricted which would mean that it could not be attached to any apparatus that would create a back pressure
• discharged at least 150mm below the air vents of the DC device, ruling out raising the hose outlet above this point
• the spillover level of any receiving vessel is at least 150mm below the air vents

Only Type DC arrangements which satisfy these requirements will be acceptable. If these conditions are not maintained the water undertaker reserves the right to require the installation of alternative means of backflow protection.

Type DC arrangements are permitted to be used on outlets in fume cupboards which are handling chemicals. But are not suitable for outlets in biological safety cabinets or microbiological safety cabinets (biosafety cabinets) used with materials contaminated with pathogens which require a defined biosafety level. Water outlets in biosafety cabinets should be fed via a Type AA, AB or AD air gap. 

For further information please refer to the advice booklet for schools, colleges and higher education establishments or contact the local water undertaker. 

Additional information: