• HPS Flooring

What is A Trench Drainage System?

Updated: Feb 7

When it comes to facility design, floor pitch and drains are often overlooked. Drainage plays a critical role in the vital factors of food and beverage facility operations.

Food safety, hygiene, and cost control are all dependent on adequate drainage systems. Having floors pitched to drains is imperative to maintaining a sanitary facility.

In a worst case scenario, poor drainage can lead to food contamination, closure of a facility. At the minimum, inadequate drainage will lead to inefficiencies and a higher lifetime cost for facility maintenance. So how do you achieve adequate drainage?

Well for one you need to have professional consultation to figure out the floor drain layout, elevation calculations, and related issues.

These professional consultations should be done with a SQF specialist or a resinous flooring expert. The layout and type of drains will be dictated by the amount and properties of liquid runoff in your facility.

Standing water is an absolute breeding ground for pathogenic and non-pathogenic microorganisms. To prevent this, the floor needs to be adequately pitched at 1-2% grade towards drains.

If it is under pitched you will end up with standing water, over pitched and you will have solids runoff. It is also important to note that this will increase the height of the floor around the perimeter of the room.

A rough estimate is, at ¼ inch height per linear foot, add 2.5 inches to the perimeter height of the room for every 10 feet from the drain. You can see how pitching the floor to multiple drains can start to get complicate which is why it is imperative to have an experienced resinous flooring expert install your floor.

This can often be mitigated by use of trenching versus point drains.

Once your facility has sufficient sloping and drains the next major concern is cleaning of the drains.

Microorganisms occur either as free form, where microbes float in the drain water, or embedded as biofilm. In either case, they create the potential for transferring pathogens, including Listeria monocytogenes from the drain to food products.

According to data from the USDA, nearly 40% of Listeria are found in floor drains in food and beverage processing facilities. To prevent this, food processing drainage systems require thorough cleaning every day.

This can include scrubbing the surface of the drain and this can be a time consuming process. You may also want to implement a preoperational ATP or other swabbing program to ensure the drains are clean prior to start-up.

A part of every auditors inspection will involve a swabbing of the drain grates so by performing tests on your own you can feel confident in the results and be proactive about any issues.

Choosing a drainage system that can minimize your cleaning and labor costs is one of the best ways to also ensure your facility will be sanitary.

Traditionally in the food and beverage industry, trench drains with hard-to-remove grates are bolted down.  In most cases, smooth stainless steel is recommended as it can handle extreme temperatures and resist bacteria.

You will also want to make sure the drains are labeled food grade, have built-in slopes to prevent standing water, have smoothed edges and rounded corners, and have sealed connections or full welded joints to prevent the growth of Listeria in non-accessible areas of the drain.

Proper drainage is also necessary for passing strict FDA and USDA guidelines. Listed below are the FDA and USDA guidelines for drainage systems.

FDA Guidelines

You should take steps to prevent the accumulation of standing water in or around drains, because standing water in your plant can be conducive to contamination with L. monocytogenes. Examples of such steps include:

  • Designing and constructing the plant in a way that will make drains function adequately;

  • Designing and constructing the plant in a way that will make drains adequately accessible for cleaning;

  • Not installing trench drains in areas where RTE foods are processed or exposed and, where practical, replacing existing trench drains with enclosed plumbing to a floor drain. Where replacement of existing trench drains is not practical, we recommend that you keep them clean and consider whether equipping them for automatic flushing would be of benefit, taking care to ensure that automatic flushing does not create aerosols that could contaminate product;

  • Designing and constructing drains so that the drains do not flow from areas where raw foods are processed or exposed to areas where RTE foods are processed or exposed. In an older plant with existing piping that has some flow from raw areas to RTE areas, you should establish systems that ensure adequate control of L. monocytogenes in the environment if you do not re-pipe the plant;

  • Designing and constructing drains so that restroom drains are not connected to drains serving areas where RTE foods are processed or exposed;

  • Designing and constructing the slope of floors to drains so that floors drain freely and water does not accumulate; and

  • Not locating sewer lines above areas where RTE foods, FCSs, or food packaging materials are processed or exposed. If this is not practical, we recommend that you take steps to protect RTE foods and packaging materials from potential leakage, e.g., by shielding the sewer lines to prevent or convey leakage.

USDA Guidelines

6-202.19 Outdoor Walking and Driving Surfaces, Graded to Drain.

  1. Exterior walking and driving surfaces shall be graded to drain

6-201.13 Floor and Wall Junctures, Covered, and Enclosed or Sealed.

  1. In food establishments in which cleaning methods other than water flushing are used for cleaning floors, the floor and wall junctures shall be covered and closed to no larger than 1 mm (one thirty-second inch).

  2. The floors in food establishments in which water flush cleaning methods are used shall be provided with drains and be graded to drain, and the floor and wall junctures shall be covered and sealed.

§ 416.2(e) Plumbing.

Plumbing systems must be installed and maintained to:

  1. Carry sufficient quantities of water to required locations throughout the establishment;

  2. Properly convey sewage and liquid disposable waste from the establishment;

  3. Prevent adulteration of product, water supplies, equipment, or utensils, and maintain sanitary conditions throughout the establishment;

  4. Provide adequate floor drainage in all areas where floors are subject to flooding-type cleaning or where normal operations release or discharge water or other liquid waste on the floor;

  5. Prevent back-flow conditions in and cross-connection between piping systems that discharge wastewater or sewage and piping systems that carry water for product manufacturing; and

  6. Prevent the backup of sewer gases.

4-204.120 Equipment Compartments, Drainage.

Equipment compartments that are subject to accumulation of moisture due to conditions such as condensation, food or beverage drip, or water from melting ice shall be sloped to an outlet that allows complete draining.

4-202.12 CIP (Clean-in Place) Equipment.

  1. CIP equipment shall meet the characteristics specified under 4-202.11 and shall be designed and constructed so that:

  2. Cleaning and sanitizing solutions circulate throughout a fixed system and contact all interior food-contact surfaces, and

    1. The system is self-draining or capable of being completely drained of cleaning and sanitizing solutions; and

  3. CIP equipment that is not designed to be disassembled for cleaning shall be designed with inspection access points to ensure that all interior food-contact surfaces throughout the fixed system are being effectively cleaned.

4-202.16 Nonfood-Contact Surfaces.

Nonfood-contact surfaces shall be free of unnecessary ledges, projections, and crevices, and designed and constructed to allow easy cleaning and to facilitate maintenance.

Having your drainage adherent to USDA and FDA guidelines is essential to ensuring a hygienic facility and avoiding a plant shutdown. To learn more check out “Importance of Cove Base in The Food and Beverage Industry."