Plumber's Licensing Exam: Indirect And Special Wastes

This guide examines the theory, purpose, and proper installation of indirect wastes and special wastes. Often, the simplest solutions to a problem are the most elegant and ideal. The indirect waste is a perfect example of a faultless solution to a problem. How do we ensure that wastewater and sewage from a drainage system do not contaminate food and related items that are being cleaned and prepared in a fixture that has to drain into that potential source of contamination? The indirect waste is the most dependable preventer of contamination devised. As long as the laws of gravity and physics remain reliable, we can always depend on the indirect waste to protect our lettuce and spatulas from sewage contamination in restaurants, among other places.

Objectives
- State the reasons for using indirect and special wastes
- Explain the practical installation of indirect and special wastes
- Identify places where indirect wastes are not needed
- Classify special wastes and explain their proper handling

Key Terms:
air gap

Objective of Indirect Waste
The indirect waste protects food that is being cleaned or otherwise prepared in a plumbing fixture. Generally, this means a sink (Figure below). In a food-handling establishment, this would mean all sinks in which food preparation may occur. A sink, or multiple compartment sink, in a smaller food preparation establishment that is primarily used for washing dishes and pots, but could be used for food preparation, will probably be required to drain through an indirect waste in order to ensure the safety of the food prepared at the site. Larger restaurants with specialized food preparation areas and dishwashing and pot-scrubbing areas will now be required to drain the dishwashing sinks through an indirect waste. In healthcare locations, sterilizers, steamers, and rinsers must be drained through indirect wastes. Any fixture that is not required to be drained through an indirect drain must be directly connected to the building drainage system. (Refer to IPC 801.1–802.4; UPC 801.0–814.3)

Real-Life Situation: Carlos, the owner of Ace Plumbing, has taken Evan, one of his installers, to his favorite diner, Dogs N Donuts, for a little visit. Carlos isn’t buying lunch though. Evan is there to install the new three-compartment sink for washing pots and pans, and the new dishwashing machine. Carlos is more of an executive than a plumber, so he doesn’t know what the code is for these fixture drains. Evan is on his own. See if you can decide how he should go about installing these drains. Then, go to your favorite diner and see if the owner will let you check out the drains at that establishment.


Figure:  Typical Indirect Waste Configuration

Often, the sink involved is a two-compartment or three-compartment commercial stainless steel sink. The drains from the two or three compartments can be connected to each other and discharge through an air gap into a receptor, or they can individually drain through an air gap into a receptor or receptors. Receptors cannot be located in bathrooms or in any inaccessible place. The distance of the air gap must be at least 1 inch or twice the diameter of the waste pipe, whichever is larger. An air gap is now the only acceptable discharge means for a sink used for the washing, rinsing, or sanitizing of utensils, dishes, pots, pans, or serviceware in the preparation, serving, or eating of food.

Tips
One of the most common complaints of restaurant owners involves the overflow that occurs when an indirect waste drains into a receptor that cannot drain fast enough to accommodate the discharge of the indirect waste pipe. Sometimes owners take things into their own hands and make a direct connection that prevents the overflow but renders the backflow prevention capability of the indirect waste useless. Be sure to properly size an indirect waste to handle the full flow of the fixture drain.
When the developed length of an indirect waste pipe is more than 30 inches long in developed length measured horizontally or 54 inches in total developed length, a trap is required on the indirect waste. This trap requirement reduces bacteria and odor in indirect wastes. No vent is required for this trap because the pipe is open at both ends and there is no direct connection to the building drainage system, and therefore no imbalance in air pressures can be created within the drainage system. Waste receptors cannot be located in plenums, crawl spaces, attics, or interstitial spaces above ceilings or below floors.
All clear water wastes must drain indirectly. These types of wastes include the many kinds of condensate that drain from refrigeration equipment, condensing heating equipment, water treatment equipment, and other such equipment. Wastewater from swimming pool maintenance equipment also falls under this same category and requires an indirect waste. Dishwashing machines also must drain indirectly. However, they can be drained through an air break or an air gap.

Figure: Air Break Indirect Waste for a Commercial Dishwashing Machine

Caution: Whenever there is a question about whether an air break or an air gap should be used, use the air gap due to the greater level of backflow prevention that an air gap affords. Remember, an air gap will always be approved in an application where an air break is accepted.

Specific Waste (Special Wastes)
Steam, water above 140°F, corrosive liquids, radioactive liquids, and toxic liquids are considered special wastes. Wastewater above 140°F is not permitted in a building drainage system. Hot wastewater must be cooled to below 140°F, usually in a retention tank, before it is allowed to flow into the building drainage system. A code official could potentially permit the use of special heat-resistant piping for water above 140°F. (Refer to IPC 803.1–803.3; UPC 810.0–813.0)
All corrosive liquids must be neutralized before flowing into a drainage system. Chemical and toxic wastes cannot enter a drainage system without being rendered harmless. Any waste that cannot be neutralized satisfactorily cannot be introduced into a building drainage system.

Fact: An indirect waste pipe is still considered to be a part of the sanitary drainage system and must meet all the other applicable provisions of the plumbing code that is adopted. Even though the indirect waste is disconnected from the sanitary drainage system, all the code provisions must be applied to the installation.

Specific Fixtures
This section outlines some of the basic requirements for specific fixtures. Some fixtures have special designs that require unique accommodations. (Refer to IPC 802.1, 802.1.6, 802.1.7802.1.4; UPC 801.2.3, 807.4, 807.1, 813.0)

Sinks
- Any sink in which food is prepared must drain through an indirect waste.
- Any sink that is used for other purposes, but would likely be used for food preparation as well, must be drained through an indirect waste.
- Any sink that is used exclusively for washing dishes, pots, and pans and will not be used for food preparation must be directly connected to the sanitary drainage system.
- Floor sinks are receptors designed and intended to receive drainage from indirect wastes (Figures below). Their design allows for many drains to go to one receptor, as long as the receptor and direct drainage piping connected to the floor sink is sized adequately.

Figure: Floor Sink

Figure: Floor Sink Diagram

Dishwashing Machines
Domestic
- In the IPC, domestic dishwashing machines can drain through a deck-mounted air gap or the drain hose must be looped up as high as possible under the countertop, following the manufacturer’s instructions.
- In the UPC, all domestic dishwashing machines must be drained through a deck-mounted air gap.

Commercial Dishwashing Machines
- Commercial dishwashing machines must be indirectly drained, but they can be drained with an air break rather than an air gap.

Swimming Pools
- The discharge from pool filter backwash must be drained through an indirect waste if the filter drain is connected to the building drain.
- If a pool drain is connected to the building drain, it must pass through an indirect waste.