Commercial kitchens are among the most challenging design projects for plumbing engineers, with a complexity comparable to the plumbing system of an entire household. More common plumbing designs, such as those in office buildings and apartments, only involve a limited number of plumbing fixture types: bathrooms, lavatories, showers, sinks and mop basins, among others. Plumbing engineers encounter these fixtures all the time and are highly familiarized with them. On the other hand, a commercial kitchen involves a more exotic array of plumbing fixtures and specialized equipment: various types of sinks, industrial dishwashers, waste grinders, soda dispensers and ice machines, to name a few examples.

Many plumbing engineers choose to specialize in commercial kitchen design. The starting point for the design process is an equipment layout with the respective specifications, requiring collaboration between the plumbing engineer and a commercial kitchen consultant. Factors such as piping size, water heater capacity and grease interceptor specifications are determined by the equipment installed.

In addition to being a demanding engineering field, commercial kitchen plumbing design is subject to requirements that vary by country or city. Given that public health is at stake whenever kitchen equipment is used, health authorities also play a role in defining requirements. In the case of New York City, requirements are outlined in the NYC Plumbing Code, NYC Building Code and standards from the Department of Environmental Protection.


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This article will provide an overview of plumbing requirements for the main commercial kitchen components.

Sanitary Drainage and Venting System

The sanitary drainage and venting system must be designed for various types of liquid waste, considering that their properties change based on the kitchen equipment that produces them. The following are some of the liquids encountered:

  • Condensates from refrigerators, air conditioners, evaporator trays, ice machines, drain pans, hoses, and cooling and plumbing lines.
  • Drained fluids from sinks and kitchen equipment in general.
  • Cooking by-products such as grease and oil, which are subject to stringent laws regarding their disposal procedure.

Commercial kitchen equipment may be required to have a direct or indirect waste connection, depending on the specific type of equipment.

  • An indirect connection leads to a private drain system, which then connects to the public sewage. An indirect connection is normally used for hot and cold storage, as well as mechanical food processing equipment. This type of connection must include a backflow prevention device.
  • A direct connection leads directly to the public sewage, as implied by its name. However, keep in mind that grease traps may be required for these connections in some cases. The direct connection is used for fixtures such as indirect waste spills, floor drains, floor sinks and mop sinks.

Plumbing vents are also an important element of commercial kitchen plumbing, providing waste pipes with an outdoor connection, typically through the roof. Their main purpose is getting rid of sewage gases, keeping them away from indoor spaces.

Hot and Cold Water Supply

Nearly all kitchen equipment requires a water supply, and there are specific requirements to meet in terms of temperature, pressure and flow. These requirements influence piping design, and also keep in mind that water may be required at a higher temperature than in normal domestic hot water (DHW) systems - leading to a larger boiler capacity.

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In addition to the specific requirements for commercial kitchens, all establishments must have an adequate potable water supply. In the case of New York, potable water requirements are defined in the State Sanitary Code, Part 5 (10 NYCRR, Ch. 1). The plumbing installation and fixtures in an establishment must be capable of delivering potable water safely and reliably to all building areas. Keeping the potable water supply clean is extremely important, preventing backflow, siphonage and cross-connection.

Isolation valves should be used to simplify maintenance, where considered necessary by the plumbing design engineer. The installation may also involve accessories like balancing valves, thermostatic mixing valves and pressure vacuum relief valves.

Use of Grease Interceptors

Guidelines for the use of grease interceptors are covered in the NYC Best Management Practices. In simple terms, grease interceptors are recommended for every direct and indirect discharge where there is a likelihood of receiving grease. This includes kitchen fixtures such as woks, food scrap sinks, meat preparation sinks, automatic dishwashers, pot wash sinks, stock kettles, scullery sinks, floor drains and scraper sinks.

Plumbing fixtures requiring grease interceptors are found in a wide range of locations: some examples are restaurants, cafeterias, butcher shops, fish markets, delicatessens, clubs, slaughterhouses and supermarket food processing areas. In general, these are non-residential locations where grease can reach the drainage system.

The following blog post will cover grease interceptor sizing and types.

Gas Supply for Kitchen Equipment

Kitchen equipment may be designed to use gas, electricity, or both. When dealing with gas, pipe sizing depends on pressure and volumetric flow rate. The gas volume is normally measured in cubic feet per hour, and is obtained from manufacturer input ratings. Also note that the NYC Fuel Gas Code applies for these installations and their related accessories.

Before initial construction or a major renovation of a food service or food processing establishment, the NYC Department of Health and Mental Hygiene may request construction documents showing kitchen equipment layout and specifications, along with plumbing installations and other required complementary systems. These reviews may be required again during operation, if considered necessary by the Department.

Conclusion

Working with qualified professionals is important in any engineering project, but especially so in the case of commercial kitchen plumbing. Requirements are extensive and very demanding, and missing them can bring legal and public health consequences. It is also in your best interest to avoid a lengthy design process with multiple revisions, since it delays the start of operations - better to work with experts who will get the design right with the first try.

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