Funky Smell? It Might Be a Dry Drain

April 19, 2023

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. 

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.

This issue is noticed more frequently in the summer and other periods with decreased activity. Lockdowns due to COVID-19, for instance, increased the number of unused drains all over campus.

While dry traps can happen anywhere, they are most often noticed in laboratories. 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. 

When planning or renovating labs, Princeton EHS recommends not installing more sinks or cupsinks than necessary, since unused sinks may develop dry traps. 

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

Downloadable Information Card

Click on image below for a downloadable PDF.

Dry drain mitigation info with information found in article.