Drainage Designs for Restaurants and Kitchens

By Michael J. Whiteside

MIFAB

Many different kinds of drainage products are found throughout restaurants and kitchens. Products such as floor drains, sanitary floor and indirect waste drains, trench drains, garbage can wash drains and cleanouts are the most common. To assist the specifying engineer, this article will review the function and application of each of these drainage products.

Floor drains

Floor drains are required throughout restaurants and kitchens to receive and drain surface water from many sources common in these areas - hose bibs, washdown areas, kettles, etc. The grating can be square or round to suit the floor design and should be of a size relative to the outlet connection size. The  ASME Floor and Trench Drain Standard, A112.6.3-2001 outlines the sizing formula for floor drains.

The grating material can be nickel bronze, stainless steel, cast or ductile iron or polished bronze. Most of the equipment in restaurants and kitchens is stainless steel; some manufacturers now provide heavy-duty stainless steel drain grates for the same cost as the industry standard nickel bronze. This provides the owner with two key benefits:

(1) Load rating - Most manufacturers' stainless steel grates and covers are heavy duty ANSI rated to withstand loads between 5,000 and 7,499 lbs. This compares to a 2,000-lb. load rating with the industry standard nickel bronze material. The benefit to the owner is less dishing of grates or covers, which is unsightly and, potentially, a trip hazard. (2) Corrosion - The material composition and properties of Type 304 cast stainless steel are such that corrosion does not occur to the same extent as with nickel bronze material. Often, one sees nickel bronze grates or covers that, over time, will tarnish to a black or gray color that no longer matches the finished floor or surrounding material finishes. This will not happen as often with Type 304 cast stainless steel.

Since there is often a large amount of debris in the kitchen and restaurant environment, it is good practice to specify a sediment bucket with each floor drain. Without a sediment bucket, the debris can enter the drainage line: This can lead to clogging and, eventually, to expensive drain line repair and maintenance. The sediment bucket will capture most of the debris passing through the strainer but must be cleaned regularly to ensure effective performance. Most floor drain manufacturers produce a type of floor drain that is designed with a sediment bucket that supports the grate. This ensures that maintenance staff cannot remove the sediment bucket permanently (because they do not want to clean the bucket regularly) since the grate will not sit flush inside of the drain without the placement of the sediment bucket.

Sanitary floor and indirect waste drains

Sanitary floor and indirect waste drains are typically manufactured of cast iron material with an acid resistant porcelain enamel coating so that they can withstand the corrosive cleaning agents that are often discharged into them during the cleaning process. For the most demanding applications, the drains are also available in Type 304 and Type 316 fabricated stainless steel. Stainless steel will provide greater corrosion resistance and durability.

The ASME Enameled and Epoxy Coated Cast Iron and PVC Plastic Sanitary Floor Sinks Standard, A112.6.7-2001 outlines the sizing formula for these types of drains.

They are designed in large sizes (12"x12" or 12" round are common), so that they have a large grate-free area to receive large amounts of wastewater. Rounded interior corners ensure that there are no obstructions to prevent wastewater from draining quickly.

The large openings also permit these drains to be used in indirect waste applications. Many codes require that drainage lines from a sink, for example, have an air gap between the sink and the drain. In these applications, a sanitary floor and indirect waste drain is often specified, since the large opening of the drain can accommodate the various drainage pipes positioned above the floor sink to ensure that there is no direct connection to the drainage line.

As with floor drains, it is good practice to specify sediment buckets with these drains to ensure that debris washed into them from the surrounding floor area does not enter into and eventually clog the drain lines.

Trench drains

Trench drains are often required in the areas between the freezers or coolers and the main kitchen area and also in areas that receive large amounts of wastewater from such sources as kettles, washdown areas, etc. The ASME Floor and Trench Drain Standard, A112.6.3-2001 outlines the sizing formula for trench drains.

Trench drain bodies and grates are manufactured of cast iron, various types of plastic and stainless steel. The bodies may be manufactured with or without anchor flanges and membrane clamps. Sediment buckets are also available and recommended with all trench drains to prevent drain line clogging.

Garbage can wash drains

Garbage can wash drains are designed to wash out the interior of garbage cans after most of their contents are disposed of through normal means. These drains provide a means for the kitchen and restaurant staff to clean the inside of garbage cans thoroughly to prevent bacteria growth. The garbage can is placed upside down on top of the drain, which has a spray nozzle and water supply that rinses the inside of the can. The drain has a 12" diameter grate (stainless steel provided by most manufacturers), a deep sump for large volume capacity and a sediment bucket as standard to capture the debris.

Cleanouts

Cleanouts are installed throughout kitchen and restaurant areas to provide emergency access to the drainage lines. This may be necessary for drain line maintenance due to the infrequent use or lack of sediment buckets in the drains. The specifier should always consider a cleanout that is designed for easy access by the maintenance person and one that can easily and effectively be resealed to prevent gases from entering the restaurant area.

As with floor and trench drains, many manufacturers now offer heavy duty stainless steel round or square covers (depending on the floor design) to provide a long lasting and sanitary product.

In summary, because of the need to drain the large amounts of water generated in these areas, restaurant and kitchen areas have a large number of floor drains. Food waste and debris often accompany this wastewater through the drains. Therefore, it is good practice to specify stainless steel grates to ensure long life and good sanitation and sediment buckets to prevent clogging in the drainage lines. Careful thought to these two design criteria will save the owner a significant cost in the long-term use of the facility.

Michael J. Whiteside is the owner of MIFAB Inc. 1321 West 119th Street, Chicago, IL, 60643, phone (773) 341-3001, fax (773)341-3046,or visit www.mifab.com. He has been with the company since 1992. He currently serves as the vice president of the Plumbing and Drainage Institute (P.D.I.). Whiteside can be contacted by e-mail at mwhiteside@mifab.com.