Employee was helping set water pump in pit sump he stepped out of way, felt something pull in lower back, stated he was ok. Continued to work through 1/6/14. Due to weather was told to stay home on 1/7/14. Employee called in on 1/7/14 said he was going to ER due to the incident that happened on 12/5/13. He received no medical treatment and no lost time till 1/7/14