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Plumbing Controls for Commercial Food Establishments

Lesson: Protection for Drains, Wells, and Septic Systems

Lesson Overview

This lesson describes the importance of and protection measures for drains, wells, and septic systems.

After completing this lesson, you should be able to:



This lesson will present information on preventing water supply contamination from:


Drains: Indirect Connections

There are two types of cross-connections for drains: indirect and direct.

An indirect connection between the water supply or food service equipment and the facility’s drainage or wastewater disposal system is necessary in most cases to prevent wastewater from backflowing into the supply or into equipment where food, kitchenware, or utensils are retained.

An indirect connection is a waste line or pipe from a fixture, receptacle, or device that discharges used water, waste materials, or sewage into the facility’s drainage system through an air gap (discussed in the previous lesson) or an air break.

An air break is a waste line or pipe from a fixture that discharges used water or liquid waste into another fixture or receptacle at a point below the flood level rim, such as the waste line from a vegetable preparation sink that drains into a floor drain.


Drains: Direct Connections

A direct connection is a waste line or pipe from a fixture, receptacle, or device that discharges used water, waste materials, or sewage directly into the facility’s drainage system.

A direct connection is permitted in a few limited instances:


Food Industry Applications

The table below lists appropriate cross-connections for drains or waste lines for various food service equipment.

Food Service Equipment Cross-Connection for Drains or Waste Lines
Booster heater for warewashing machine Air gap between the relief valve vent pipe and the floor drain or floor sink
Water-cooled compressor for an ice machine or other refrigeration system Air gap between the end of the supply line and the floor drain or floor sink
Drain lines for:
  • Salad cooler table or salad bar
  • Soda fountain/dispenser ice bin
  • Steam kettle or steam table
Air break
Condensate drain lines for refrigeration equipment Air break
Water softener with a brine tank that drains through a hose bibb Hose bibb vacuum breaker
Water softener with a brine tank with a gate or ball valve Air gap


Grease Interceptors and Traps

Oil and grease from foods and cooking processes entering a facility’s drainage waste system will eventually solidify somewhere downstream and clog the sewer line and/or cause potential problems onsite or in the public sewage system.

To prevent this, oil and grease in wastewater is collected in grease interceptors or grease traps. Grease interceptors are usually installed inside the establishment and may be any size. Grease traps are outside the establishment and must be a minimum of 1,000 gallon capacity.

Types of Oil and Grease


Grease Trap Size and Location

Grease trap installations are designed and sized based on anticipated flow rates and organic load for maximum efficiency. The size needed depends on:

Regardless of size, the trap should be:



The main types of wells are:


Reducing Contamination in Wells

Regardless of the type of well used as a water source, the following steps can help reduce the risk of contamination:

Contamination Threats to Wells

Shallow wells, such as dug and driven wells, are relatively easy to contaminate. Possible contaminants include:


Septic Systems

The main components of a septic system are:

As septic tank effluent percolates through the drainfield, soil microorganisms treat wastewater physically, chemically, and biologically before it reaches the groundwater, preventing pollution and public health hazards. In most cases, the wastewater requires no further treatment before reaching the underlying groundwater level.


Risks Related to Septic Systems

If the drainfield soil is overloaded with water, or when a specific contaminant cannot be treated by soil microorganisms, the quality of the underlying groundwater may be affected.

When septic systems do not function properly, the risks include:

Indicators of septic system problems include:


Managing Septic System Risks

To minimize risks associated with septic systems, ensure that:



Select the following links for more information on plumbing controls for commercial establishments:


Lesson Summary

This lesson described the importance of and protection measures for drains, wells, and septic systems.

You should now be able to: