Keep Drain Traps From Drying Out

Oct. 7, 2019

Recently, there have been several instances of unpleasant odors in laboratories that have elicited calls to EHS. In each case, the cause was dry sink and floor drain traps. 

Drains are equipped with a U-shaped pipe, called a trap, which blocks odors when full of water. Infrequently used drains and sinks will dry out, allowing these odors (usually a rotten egg, sewer, or occasionally gas, chemical or solvent odor) to escape. 

Dry traps can—and do—happen anywhere, eliciting nervous calls to plumbers from homeowners with out-of-the-way utility sinks or basement floor drains. They are more often noticed in laboratories, however. Most labs are kept in negative pressure, allowing air to circulate up and out fume hoods and ventilation systems. This makes it more likely that odors will be drawn out of dry traps. 

The solution to this problem is simple—run water in all sinks periodically or pour water down floor drains from time to time (once a month is recommended). This will keep the traps wet, preventing odors from escaping.  

When planning or renovating labs, Princeton EHS recommends, “Do not install more sinks or cupsinks than are necessary. Unused sinks may develop dry traps, resulting in odor complaints.” 

Read more health and safety design tips for laboratories on our website: