During most laboratory design projects, there eventually will be a discussion about drains at the safety shower locations. Many shower manufacturers recommend floor drains be provided, and my thoughts here may be met with some scrutiny from many of my lab planning colleagues, but my very short answer to the question of including drains is usually an emphatic “No”.
Let me offer a few facts and opinions for consideration:
The shower is for emergency-use only. Hopefully it is never used, except for your routine flow tests. In reality, you’ll be using large containers to capture water during testing and minimal, if any, water should get on the floor.
Floor drains will not effectively collect the water deluge released from the shower. ANSI Z358.1-2014 sets the requirements related for these devices. The shower must deliver 20 gallons of water per minute, for a minimum of 15 minutes. A 15-20-minute rinse time is recommended for moderate to severe irritants and chemicals that cause acute toxicity if absorbed through the skin, 30 minutes is required for most corrosives, and 60 minutes for strong alkalis.
For reference, 20 gallons/minute is about four times the flow of a standard hose bib or home shower head. A 20-minute shower would disperse about 400 gallons of water. That begs the question, where does all the water go once released? ANSI requirements (Section 4.14) state that the water pattern is at least 20” in diameter, 60” above the floor. That means a large majority of the water won’t make it to the drain, but rather to the lowest point of the floor in the lab. So, in reality, the drain piping doesn’t need to be sized for 20 gallons/minute.
Hazardous Waste. If you need a safety shower in your lab, I assume you have hazardous chemicals in that space. Any hazardous waste that may go into the sanitary sewer should be routed through a neutralization station or into a hazardous waste collection tank. Proper chemical resistant piping from floor drains will likely be required.
Mitigating sewer gases. All drains require traps but that doesn’t mean that traps always work perfectly. Trap seal loss will allow methane to pass into occupied space, thus creating a potentially dire health and safety consequence. A guaranteed source of water to maintain this trap seal must be assured by the designer. Mineral oil is commonly used to prime the traps because, unlike water, it doesn’t evaporate. There are several alternative trap priming devices available, however most can be expensive and/or require maintenance that owners aren’t usually interested in. The Trap Guard® device, relatively new to the market, is a reasonable option to consider if you require or desire a drain.
Dishing or sloping the floor to drain. If a floor drain is required or desired, can it be recessed in the floor or perhaps could the whole floor even be pitched toward the drain? Admittedly, I haven’t worked with a client to date who believes this is a clever idea. However, I believe the potential for chemical spills in a lab is greater than the potential for someone to have to shower in the lab, and we’d like to avoid chemicals accidentally going down the drain.
While some local plumbing codes, campus or company facility guidelines may require installation of “emergency drains,” read the language carefully and consider a conversation with the AHJ (Authority Having Jurisdiction) early in the design process.
S+T Lab Expert Contributor