If you are using mod_jk you can disable a worker. If a worker is disabled, mod_jk will route requests for existing sessions to it, but will not route requests for new sessions (unless there are no non-disabled workers available).
http://tomcat.apache.org/connectors-doc/reference/workers.html discusses this. Look for the 'activation' property (for mod_jk 1.2.19 or later) or the 'disabled' property for earlier mod_jk releases.
Thanks for the quick response. We do use mod_jk for load balance.