When do they switch sides in beach volleyball ?

Question

has to do with score, but I can't figure the pattern

Answer 1

Every 7 points.

Answer 2

I assume your watching the olympics.

They play best of 3.  The first two games are up to 21, the third tie-break game is up to 15.

When the game is up to 21, they switch every 7 points.  The final tie-break game they switch every 5 points.