Why does our unit smell like rotten eggs after a hot weekend?

The rotten egg smell in your standard portable toilet is caused by hydrogen sulfide gas, which is produced by bacteria in the holding tank when waste breaks down in hot, low-oxygen conditions. High heat accelerates bacterial activity, and a fresh service on Thursday means the tank had a new supply of waste that began decomposing rapidly during the 90-degree weather. The deodorizer blocks odors by masking them and slowing bacterial growth, but it can be overwhelmed by extreme heat and heavy use. For a family of four, the usage is reasonable, but heat is the main factor here.

There is little you should do between service visits. Do not add household chemicals, bleach, or extra water, as these can disrupt the deodorizer's chemistry and make odors worse. Keep the door and vent closed to minimize oxygen entering the tank, which fuels the bacteria that produce the gas. If the odor persists, contact the rental company. They may need to increase the service frequency during hot spells, which is a common adjustment for summer rentals.