The level of sheep scab has increased in recent years as many farmers have moved away from plunge dipping in favour of low labour, pour-on products.

As useful as these pour-on products are, only plunge dipping using correct methods will help to eliminate sheep scab. Whether it be constructing a new dipping tank or upgrading an existing one, there are several factors that farmers can work on to reduce labour and improve the safety of dipping facilities.


The fundamental consideration when laying out a dipping tub is the environment. Dipping tubs should not be located near watercourses of any description, nor should they be located in an area where spillage may flow towards a watercourse.

It is best to source a precast concrete or plastic dipping tub, as it is difficult to construct a fully leak-proof tub using blockwork plaster.

For operator safety, dip tubs should not be located under a roofed area, nor should there an outlet pipe for emptying tubs at their base.

A forcing pen is essential within a handling yard operating a dipping tub and it should be located either in front of the dip tub or used to funnel sheep into a race leading to the tub. This pen can be circular with two gates hung on a central post, which allows them to revolve round continuously with latches at various points. For very small flocks, a semi-circle or funnel-shaped pen may be used. A space of 0.3m2 per animal should be allowed. Surrounds should comply with clauses 5 and 6 of the Building Regulations.

Depth and size

Dipping tubs should be 1.1 metres in depth. Dip tub size should be related to flock size. A 1,050-1,250 litre capacity tub is suited to flocks of 100-250 ewes and can handle one /two sheep at a time. Larger flocks of 250-500 ewes will require a 1,818-2,000 litre capacity tub, capable of holding three or four ewes or five/six lambs at a time. The Department specifications state that the dipping tub should contain a minimum of 2.25 litres/animal dipped.

Larger dipping tubs are more costly to prime. Long dip tubs are 7.6 metres to 12.5 metres long with the theory being that the sheep will be sufficiently dipped after walking down the ramp and swimming through the bath.

The long swim bath allows continuous dipping and reduces handling, but are very expensive to build and fill. To justify the cost, a dipping rate of 500 ewes per hour is required, ruling them out for nearly all Irish farms.

But whatever the size, the tub should allow ease of access for a tractor and vacuum tanker to remove spent dip or replenish a tank with clean water. The spent dip should be diluted and spread as per the dip manufacturer’s instructions.

With an average flock size in Ireland of roughly 100 ewes, the most cost-effective method of setting up a dipping tub is to locate the tub at the edge of a semi-circular forcing pen. Sheep can then be manually placed in the tub, but full PPE is essential to protect the farmer from splashing.

Draining pens

The exit should be stepped with a guillotine gate in place to allow sheep to exit through to a draining pen without the operator having to cross over/close to the dipping tub each time. Two side-by-side pens are recommended, with 0.5m² required per ewe. Flocks of 100 ewes should have 15m² of draining pens, equating to 30% of the flock. Floors should be of non-slip concrete construction of 100mm depth, with a slope of 1:60 directing drained dip back towards the dipping tub. The edges of the drainage yard should be tapered towards the dipping tub, with kerbing installed at gateways to prevent leakage.

In brief

  • Plunge dipping is the only effective control for sheep scab.
  • Dipping tubs should be between 1,050-1,250 litres capacity or 2.25 litres for each sheep.
  • Locate the tub close to main sheep grazing block.
  • Ensure good access for vacuum tanker for emptying/filling the tub.
  • Slope draining pens 1:60 back towards the dipping tub.