When a party to an arbitration becomes aware of facts showing the arbitrator is biased, the party must give notice of the arbitrator’s disqualification before a hearing of any contested issue of fact relating to the merits of the claim or after any ruling by the arbitrator regarding any contested matter.  CC\P 1281.91(c).  Here, the arbitrator revealed that the father of the defendant’s attorney had been his mentor.  Plaintiff took no step to disqualify the arbitrator after that disclosure and so waived any bias.