How many PWD toilet stalls are needed if there are 20 water closets for female users?

The correct number of PWD (Persons with Disabilities) toilet stalls required when there are 20 water closets for female users is one, which aligns with the standards set by accessibility regulations. Typically, building codes stipulate that when there are a certain number of water closets designated for one gender, a sufficient number of accessible facilities must also be provided to ensure inclusivity for individuals with disabilities.

In this case, the requirement typically calls for at least one accessible stall when there are a specified minimum number of other stalls available. Given that 20 water closets provide ample capacity for female users, having one PWD toilet stall meets the legal requirements while ensuring that individuals with disabilities have equal access to restroom facilities.

As a reference, most building and accessibility codes typically dictate that one accessible toilet stall must be constructed for every group of a certain number of standard stalls (often starting at 6-20 stalls). Thus, having one stall would sufficiently accommodate the needs of those who require accessible facilities.