OSHA and eye wash station checks

I have a physician client who is conducting weekly eye wash station checks. In a conference earlier this year attending by the office administrator, it was mentioned that medical practices need to be doing these checks twice a week to meet OSHA standards. However I have not been successful in finding this regulation and a person I know in a hospital system says you only have to do it weekly.

The "testing" of the eyewash stations is really 3-fold in it's purpose:

1) You want to make sure it works.
2) You want to make sure the water temperature is appropriate.
3) You want to flush the lines weekly, to assure that nothing is growing in the stagnant water in the line.

These three measures assure the safety of the worker who runs to the station, turns it on and flushes their eyes in an emergent situation. I'm not seeing (no pun intended) the purpose of a bi-weekly test - unless you've cultured the water and found that you have something that grows on a more frequent basis.

Thoughts?