Water, water everywhere and not a drain in sight: a primer on kitchen drainage

Nation's Restaurant News, March 18, 2002 by Foster Jr. Frable

The quantity and variety of drains found in a commercial kitchen differentiate it from almost any other type of retail or commercial facility. Almost every piece of equipment in a kitchen can be moved or changed, but since drains usually are cast in the floor slab, they are there almost forever. Therefore, it is important to plan and install the proper type and number of drains before the floor is constructed.

Each type of drain used in a commercial kitchen has its own purpose and application. General-purpose-area drains are used for floor cleaning and catching standing water. Funnel wastes, hub drains, stand pipes and floor receptors capture condensate from refrigeration equipment and waste from food-prep sinks. Trough drains are used in front of steam kettles, braising pans, and ice machines and in other areas where they need to handle large quantities of liquids that may be poured over a wide area.

Most foodservice drainage falls into two categories: direct and indirect. Examples of direct drains include hand sinks, prerinse and pot sinks -- through grease traps -- and bathroom lavatories. Direct drains usually include a U-shaped device called a trap to prevent sewer gases from returning to the kitchen.

Indirect drains are the most common drain in foodservice since they provide a gap of open air between the drain and the pipe going to the equipment. They are required in most health and building codes for any sink used for food preparation, condensate drains from refrigeration coils and cooking equipment and any other device where back flow from the waste line could come in contact with food.

The two most common indirect waste drains are funnel drains and floor sinks. Funnel drains have a brass or stainless funnel welded on one side of the grate. Funnel drains function well for applications with limited flow, like condensate drains and beverage equipment troughs, but they often are overwhelmed by drains from dishwashers and large prep sinks. Floor sinks or receptors are popular because they serve three purposes: as general-area drains, as collectors for indirect drains from equipment and as reservoirs to buffer higher flows of liquids before they enter a small drain pipe.

When using floor sinks, one needs to verify local code requirements. Fifty years ago most plumbing codes required that the rim of floor sinks be raised 2 inches above the floor surface. That stipulation was intended to prevent fish scales and sawdust used to collect the blood from butchering from clogging the drain. Since very few commercial foodservice operations today butcher meat or fowl or use sawdust on the floor, that requirement was relaxed or eliminated in most areas. However, in some municipalities the codes remain on the books" but rarely are enforced, except in commercial meat-processing shops.

Problems occur when building inspectors and engineers who may not be familiar with commercial kitchens interpret the code as applicable for every kitchen. The result can be a disaster if a kitchen is planned with floor sinks intended to provide a dual purpose of both general drainage and indirect waste. If the plumber installs the floor sink rims above the floor, the kitchen will have no area drainage to which water can be mopped or brushed when the floor is hosed down. The raised drains become a hazard in work areas and aisles. The local "attitude" regarding raised or flush floor sinks needs to be verified carefully before you begin construction of a new kitchen or its renovation.

Drains are intended to eliminate puddles of liquid on floors and should reduce slips and falls, not contribute to them. When drain covers rise above the floor or are constructed with highly slippery material, such as stainless steel, they can create more problems than they may resolve.

The top surfaces of drains should be as slip resistant as possible, whether it be through the use of "file finish" stainless or fiberglass grates with an abrasive finish for floor troughs or sand finish castings on a floor drain in a traffic area.

Most codes require drains from dish-wash prerinse and pot sinks to be connected to a grease interceptor - a recessed or surface-mounted tank with baffles to collect the grease before it can clog pipes downstream from the kitchen. Some health and building departments now are mandating that all drains in food preparation areas where grease might be present also be connected to the grease trap. That requirement significantly increases the size and cost of the grease trap and mandates a dual-drainage system under the slab.

Drainage systems are a critical part of any commercial kitchen. Missing or improperly installed drains affect safety, with slips and falls on fallen ice or standing water; sanitation, when drains are clogged, and floors and equipment cannot be washed down; and even the day when you open for business, when the health department withholds approval of the facility. Since drains are very hard to add or change after installation, make sure that they are properly planned from the beginning, including meeting all code requirements.