Water Supply Industry Interpretations and Advice

  • Area of Interest : Backflow prevention
  • Topic : Fluid category
  • Title : Backflow risk assessment for allotment hose union taps:
  • Clause Reference : Schedule 2 paragraph 15 & G15.3
  • Reference Number : B28
  • Decision Date : October 2003

Where a hose union tap on an allotment garden is used in accordance with the following conditions, it can be considered as being of no greater risk than the equivalent tap in a domestic garden. That is to say that would be categorised as a fluid category 3 risk. If these conditions are not met or do not apply a risk assessment will be required and may result in a higher level of backflow protection due to the increased risk.


  1. Hoses will be hand-held in use, with “fail-safe” means of flow shut-off (i.e. self-closing trigger mechanism) or, if connected to irrigation systems, will have fixed sprinkler heads or outlets not less than 150 mm above ground and will not use additives (fertilisers, pesticides).
  2. Hoses are permitted to be used with hand-held sprays containing readily available domestic fertilisers (but NOT insecticides or herbicides etc.);
  3. Seep hoses in direct contact or less than 150mm above the soil are considered to be a fluid category four backflow risk and must not be connected to a mains-fed hose union tap equipped only with a double check valve. These may be permitted when used with a type DB pipe interrupter (Refer to G15.23 of the Defra Guidance for further information) or other fluid category 4 protection device.
  4. Garden chemicals: where the formulation and concentration of chemicals used by allotment holders are the same as those available for purchase and use in domestic gardens.
  5. The use of animal wastes (farmyard manure etc.) is possibly greater on allotments than in domestic gardens, but these materials are used on soils in domestic gardens and the risks from their presence are similar.
  6. Presence of drains etc. into which hoses could be immersed is considered to be no more likely than in domestic gardens.