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Equipment washroom design advice

20 March 2023

David Childs discusses best-practice for the design of equipment washrooms on food manufacturing sites.

Incorporating a hygienically designed equipment washroom into a food and drinks manufacturing facility is fundamental to its hygiene function.  If effectively managed it will ensure any equipment processed through the facility can be decontaminated to eliminate/reduce hazards (microbiological, chemical, physical and allergens) to safe levels and ensure that label claims are also adhered to.

The washroom should be segregated from manufacturing areas (food storage, processing, and packaging areas) to prevent any risk of spreading hazards during the cleaning process into surrounding manufacturing areas. 

The washroom should be designed so that it can be maintained in a clean and hygienic condition and should be constructed of corrosion resistant materials. Fabric that may be subject to damage should be protected and the facility should be easy to clean and have adequate supplies of hot and cold rinse water, compressed air (to operate chemical supply satellites) and cleaning and disinfection chemicals – ideally supplied pre-diluted. The facility should also be watertight to prevent egress of fluids into manufacturing areas.

Walls, floors, ceilings, drains and doors must be designed, constructed, and maintained so they do not pose a risk to any of the manufacturing equipment being decontaminated within the washroom facility. 

Floors are areas where microorganisms, such as Listeria monocytogenes, could persist so it is vital that they are impervious, non-absorbent, non-toxic, robust, resistant to chemicals, resistant to temperature and thermal shocks, made of slip resistant material and contain minimal floor joints which can deteriorate over time, especially in wet environments. Most floor resins can be laid without floor joints, providing that the substrate concrete is jointless. Heavy duty polyurethanes work particularly well in wet environments. 

Floors should allow adequate surface drainage of cleaning fluids to prevent pooling fluids which can result in microbiological issues, chemical degradation and potentially slip accidents. The fall to drain on a washroom floor is greater than that found within other manufacturing areas due to the amount of cleaning fluids in use and a typical floor fall to drain should be up to 2% (<20mm/metre). The floor should fall away from all walls and doorways to prevent fluids from collecting around the extremities of the room, eliminating challenges at the wall/floor interfaces and reducing the degree of soiling on the floor.

Drains should be present in every partitioned area within the washroom to allow cleaning fluids to drain away during area environmental deep cleans. The drains should be accessible for cleaning and proofed to prevent any pests from entering the facility. Drains should also be designed and large enough to cope with the volume of fluids being generated within the rinsing areas, to reduce the risk of wastewater backflow and to ensure the water level does not rise above the drain. 

They should be manufactured from stainless steel, be fully drainable, feature continuous welded joints and rounded corners with no crevices or dead spaces and should incorporate an air lock which acts as a barrier between the washroom and the effluent system. Sediment baskets should be in place to catch any debris which may enter the drain channel. 

Drains should always flow from the high hygiene areas (decontaminated equipment storage area - clean room) to medium hygiene areas (the main cleaning and disinfection area) and finally through to the dirty equipment storage area).  

Drain design and accessibility is important when designing a washroom to ensure the drains can be routinely inspected and decontaminated. The drain baskets in the main cleaning area will require routine emptying to reduce the risk of the drains overflowing. Care should be taken when decontaminating any drains within a washroom facility. Dedicated colour coded cleaning equipment and PPE should be used during this process and drain parts should be decontaminated off the floor within a dedicated colour coded vessel and not within any of the other washing facilities in the washroom.

Walls within washrooms can be subject to damage so it is important to ensure wall panels are manufactured and installed correctly and protected from damage. 

Wall panels designed to be impervious, smooth, hard wearing; resistant to fire; resistant to corrosion and chemicals; and suitably strong and stable should be used. These can be further protected from damage by cladding with stainless-steel sheets to provide protection, improve the washroom aesthetics, provide some thermal resistance, and allow the panels to be easily cleaned and disinfected.

Wall-to-wall, wall-to-ceiling and wall-to-kerb joints must be sealed, with tight fittings and waterproofed with no visible cracks or crevices. The wall panels should be positioned and sunk into prefabricated kerbs to reduce the risk of any floor damage compromising the internal fabric of the wall panel. Kerbs should incorporate a sloped top edge to allow cleaning fluids to run off and prevent soil building up on the surface. 

To separate the washroom facility from manufacturing areas, suitable doors should be installed which must be kept closed when the facility is in use. An air lock featuring sliding doors would be preferable over other alternative barriers, such as strip curtains or rubber swing doors, which are not as effective, particularly if there is a requirement to maintain positive air pressure within the clean equipment storage area and negative pressure within the main cleaning area of the washroom.

Doors should be easy to clean, impervious, smooth, tough and resistant to chemicals, corrosion, and thermal shock. They should be close fitting to the floor, with a maximum clearance of ~ 6mm. Hollow rubber door base seals should be avoided, as these can act as harbourage points for soil, moisture, pests and microorganisms. 

Ceilings should be manufactured from smooth, impervious, durable, fire resistant, corrosion and chemical resistant sandwich type panels and installed to at a height of at least 3m to help prevent condensation, facilitate air flow, and allow for easy access for cleaning. 

The junctions between the ceiling and the wall panels need to be rounded, sealed and cleanable. Any pipes that feed into the washroom from service voids should be well sealed, with a sealant or a collar and all throughputs should be vertical.

Adequate lighting – ideally integrated into the ceilings to eliminate a soil harbourage area – must be in place to enable the hygiene staff to operate safely but also to ensure good visibility for the inspection of equipment. For inspection areas, recommended illumination levels should be between 550-1500 LUX (lm/m2). Shatterproof light bulbs and shatterproof watertight covers should be used to eliminate the risk from broken glass.

To control humidity levels and reduce the risk of condensation formation and subsequent microbial growth to control odours and to ensure there is suitable visibility for the staff carrying out the cleaning and inspection of equipment, suitable air handling systems need to be installed, separate from any installed in other manufacturing areas. 

The extraction systems should be powerful enough to ensure that there is always clear visibility during cleaning and to maintain a negative pressure (extraction rate is higher than the supply rate) to retain cleaning residue aerosols within the main cleaning area. Air change rates within the main cleaning area should match the predicted moisture load in accordance with the room temperature (higher the temperature the higher the water holding capacity of the air). Humidity and temperature levels can be assessed within the washroom using a simple humidity/temperature meter.

Position and flow
During the design process, there should be consideration with regards to the flow of equipment through the facility. 
To ensure equipment being decontaminated within the washroom is not cross-contaminated during the cleaning process, segregation between dirty equipment waiting to be cleaned, equipment that is being cleaned and finally equipment that has been fully decontaminated, is vital. Through effective design, the washroom can be laid out to facilitate this process – ensuring cleaned equipment never comes into contact with dirty equipment.

To ensure there is no crossover between dirty equipment and equipment that has been fully decontaminated, there should be separate entrances and these should be labelled accordingly.

There should also be partitioned areas within the washroom to reduce the risk of cross contamination during cleaning.

Finally, It is best practice to position the washroom as close to external factory walls as possible. This will reduce the length of extraction pipework, as exhaust vents will be on external walls, venting to atmosphere. 

David Childs is Technical Services Manager at Kersia UK.

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