Pesticides - Best Practice Guides

After 
Spraying

Sprayer Cleaning


Why Sprayer Cleaning Matters?

Good sprayer cleaning is essential as it avoids risks to other crops sprayed and ensures the sprayer is ready for the next job. It is especially critical after using herbicides where even tiny traces of chemical left in machinery can damage later sprayed crops. Washing also helps avoid blockages. Using pesticides according to the label and following best practice should ensure their impact on the environment is minimised, however there is clear evidence that poor practice when cleaning up after spraying can pollute surface and groundwater. To reduce the risk of Groundwater contamination any disposal to land of surplus spray and washings that does not take place in the crop requires a Groundwater Authorisation from the office of the local environment agency.

The Sprayer

  • The Sprayer manual will give guidelines on best washing procedure. Use this advice together with any specific product advice;
  • Sprayer cleaning can be speeded up dramatically by tank rinse nozzles. They allow the job to be done in the field quickly with minimal water
  • Electronic rate measuring devices can help you spray accurately and ensure a suitable area is left for placement of tank washings if required;
  • A hose and brush attachment, which is available on some sprayers, can be used to clean the outside;
  • Remember it is easier to clean the sprayer before any spray solution has dried on to the sprayer.

Keep Water Clean

  • Make sure that streams and watercourses are not contaminated;
  • Never pour pesticide in any form (including pack washings) into soakaways, sewers, drains, ditches or rivers etc.

Where to clean the sprayer ?

The best place to clean the sprayer is on an unsprayed or under dosed area of the field last treated. The field is also the best place to clean the exterior of the sprayer. Cleaning the sprayer in the field does not require a Groundwater Authorisation. It is also possible to clean the sprayer in the farmyard; however any washings must be collected and sprayed back on the crop. Advice on pesticide handling facilities is included in the CPA Guides on Pesticide Handling Areas and Biobeds.

Disposal of any washings to a site other than a crop for which the pesticide(s) is approved will require a groundwater authorisation. A Groundwater Authorisation application pack can be obtained by contacting the relevant environment agency . These sites may only be used after approval by the office of the local environment agency. Authorisation will only be granted if there is no risk of surface or groundwater contamination.

Environment Agencies

Environment Agency (England & Wales)
0845 933 3111

Scottish Environment Protection Agency www.sepa.org.uk

Environment and Heritage Service, Northern Ireland
www.ehsni.gov.uk

Preparation before Spraying

  • Check the sprayer is clean
  • Sequence spraying operations to minimise the number of rinsing operations needed
  • Make sure the sprayer is calibrated
  • Check the product label for any special cleaning advice and warnings about sensitive crops
  • Mix enough pesticide for the job, just too little is better than too much
  • Identify when and where you will be cleaning the sprayer
  • Choose an area of crop suitable for spraying out washings; make sure there is no risk of exceeding the maximum recommended dose by washing out in the field

After Spraying

  • Ensure sprayer and spray tank are empty
  • Remember to wear face shield, coveralls and gloves especially when cleaning the exterior
  • Clean the sprayer at the end of the spraying every day; if you are using the same product on consecutive days it may not be necessary to do a full clean
  • Use clean water to clean the sprayer thoroughly and follow the procedure overleaf
  • Make sure the sprayer is drained when you have finished
  • Dont forget to clean the outside of the sprayer with clean water and a brush; wet fresh deposits are easier to remove and is two minutes well spent at the end of the day
  • Store sprayer under cover especially if it has not been possible to clean the exterior
  • In frosty weather and before long term storage it is a good idea to conduct the last rinse with some anti-freeze in the rinse water

Standard Sprayer Cleaning Procedure

Sprayer manuals and product labels should be carefully checked for special cleaning procedures. These may be necessary for specific machines or chemicals and should be closely followed. Otherwise the following procedure is recommended:

1. Surplus spray solution should be diluted with at least 10 parts clean water and sprayed onto a part of the field which has been treated at less than the maximum recommended label rate.

2. Thoroughly hose all the inside of the spray tank with clean water, including the tank top and lid. If tank rinse nozzles are fitted then follow the manufacturers instructions. Re-circulate the rinse water within the sprayer (i.e. pump, agitation system, control unit, pipes and the induction hopper) for a full 2 minutes.

3. Spray the rinse water out of the sprayer. If washing in the field, spray onto an area as described in Disposal of Washings (below)

4. Remove suction, main and in-line filter elements. Wash thoroughly in clean water with a soft brush. Re-assemble filter housing without filter element.

Tank Cleaning Procedure

If tank rinse nozzles are fitted: Add clean water to the spray tank until it is approximately a quarter (25%) full then mix in a cleaning agent recommended for sprayer decontamination at the correct dilution rate for the volume of liquid in the spray tank. No further water needs to be added. Use the tank rinsing nozzles and recirculate for 2 minutes and spray out as described in Disposal of Washings (below)

If tank rinse nozzles are not fitted: Add clean water to the spray tank until it is approximately a quarter (25%) full then mix in a cleaning agent recommended for sprayer decontamination at the correct dilution rate for the full volume of liquid in the spray tank. Fill the sprayer tank to the brim and then re-circulate for 2 minutes and spray out as described in Disposal of Washings (below).

NB Some herbicides must be deactivated with ammonia-based agents and may require leaving in the tank for a short period check the label. Do not mix chlorine and ammonia based cleaning agents.

1. Remove the boom end caps and repeat the Tank Cleaning Procedure but without the cleaning agent

2. Wash the outside of the sprayer with clean water. A low volume washing brush is more effective and uses less water than a high pressure spray gun

3. Remove nozzle and nozzle filters, and scrub clean with a soft brush. Refit these and the other filter elements

4. Completely drain tank, spray booms and all water pipes

Hot Spots for Cleaning - Don't Forget

Key areas where spray solution can remain after the initial clean are: the sump, the pump, all pipe work, filters and the induction bowl . The areas most likely to have spray deposits on the outside of the sprayer are the booms, the back of the tank and the rear wheels.

Disposal of Washings

Provided the treated crop has not received the maximum dose, it is possible to put the washings back onto the crop. It is important to ensure that the statutory maximum dose on the label is not exceeded. To make sure you have a suitable area either leave a weed/pest free area untreated or under dose a selected area. Alternatively spray out onto another approved crop but remember not to spray out onto a sensitive crop or land intended for cropping with a sensitive crop.

Otherwise washings may only be disposed of onto an area, such as a Biobed, that has a Groundwater authorisation from the office of the local environment agency.


The advice in this Guide has been prepared after consultation with the Pesticides Safety Directorate, the UK environment agencies and equipment manufacturers.
This guide was produced by the Crop Protection Association as part of The Voluntary Initiative.
The Voluntary Initiative is a programme of measures agreed by Government to minimise the environmental impact of pesticides.

(C) Voluntary Initiative November 2003

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