The default installation directory is as follows:.
/opt/Symantec/symantec_antivirus
The default work directory for LiveUpdate is as follows:
/opt/Symantec/LiveUpdate/tmp
Q. Common Disk space requirement for SEP for Linux.
A. Our documented disk space requirements can lag behind the state of our product and the maximum size of a definition update download. Please ensure that sufficient disk space is available in /opt/ and /tmp/. According to most recent testing with SEP 12.1 RU6, total pre-installation space requirements are about 9GB for /opt/ and 1.5GB for /tmp/. The /tmp/ requirement and about 4GB of /opt/ are needed for working space when updating definitions.
See here for reference:
Symantec Endpoint Protection for Linux Frequently Asked Questions (SEP for Linux FAQ)