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I visited with our facilities’ safety officers about the questions regarding drains for safety showers and he brought up some additional items that were not mentioned in the earlier discussion. The following is from his message back to me (by the way, a POTW is a publically owned treatment works):
Some do not install floor drains in labs, even under safety showers, in order to avoid having chemical spills make their way to the sewer system. Some jurisdictions are apparently adamant that spills, even small ones, do not occur to the sewer system. We took this approach when we built our main lab building but have since changed back to putting floor drains in labs under safety showers. My thoughts are that a lab spill would be a small spill - one that might be a small regulatory breach but not cause environmental damage if the small amount of chemical(s) made their way to the sanitary sewer. Again, some POTWs will not accept any such chemicals to their system and apparently so not allow such floor drains. That is not the case here.
Major spillage, especially from fire conditions are another issue, of course. Lab-scale chemical spills, along with fire sprinkler water, from a laboratory will likely make its way to the environment untreated, via sump pumps, etc. under such conditions. Personally, I would rather see this "lightly" contaminated water pass through the POTWs treatment system before entering the environment where much of it will be handled biologically or via much greater dilution before entering the environment.
Some issues with floor drains under showers are:
- They, more often than not, become a nice place for dirt to drop when floors are swept/dry mopped. The drains tend to become plugged so liquids will not pass through anyway. This can be avoided by good maintenance practices, of course.
- Drain traps tend to dry out and allow sewer gas to enter the building if not maintained wet or with a special seal.
- According to ANSI/ISEA Z358.1-2009, emergency showers are supposed to flow at a rate of at least 20 gpm. Drains installed under them may not be designed to handle the large volume of water put out by these systems, especially if the shower and eyewash are tied together in the same drain pipe.
Hope this sheds some light on the subject.
Nicholas V.C. Ralston, Ph.D.
Health Effects Research Program Leader
Energy & Environmental
In order to understand a system, you must first understand the system of systems that comprise each system.
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