CUSTOMER STATED : Lavatory sink will not drain. TECHNICIAN NOTES : Out today for the tenants concerns of the full guest hallway bathroom lav sink not draining. Water will begin to backup after running for 5-10 seconds. While performing maintenance inspection, found both hose bibs to be piped before the prv. Prv located in the crawlspace. Water pressure from water heater tested at just below 80 PSI. RESOLUTION : Ran small sink machine and pulled back hair / some type of wipe material. Sink is now draining as it should after retrieving hair and wipe. Sink has ran for just under 19 minutes to properly test and is showing no further concerns at this point in time.