Long-term mortgage rates fell for the third week in a row, with 15-year fixed-rate loans hitting a new record low and the 30-year fixed-rate hovering at just above 5 percent, Freddie Mac said in releasing the results of its weekly Primary Mortgage Market Survey.

The 30-year fixed-rate mortgage (FRM) averaged 5.04 percent -- with an average 0.7 point -- for the week ending Sept. 17, Freddie Mac said, down from 5.07 percent last week and 5.78 percent a year ago.

Rates for 30-year fixed-rate loans hit a record low of 4.78 percent in April, in part due to the Federal Reserve's commitment to purchase up to $1.25 trillion in mortgage-backed securities issued by Fannie Mae, Freddie Mac and Ginnie Mae.

The 15-year FRM this week averaged 4.47 percent with an average 0.6 point, down from 4.5 percent last week and 5.35 percent a year ago. It's the lowest the 15-year FRM has been since Freddie Mac started tracking it in 1991.

Five-year Treasury-indexed hybrid adjustable-rate mortgage (ARM) loans averaged 4.51 percent with an average 0.5 point, unchanged from last week and down from 5.67 percent a year ago.

One-year Treasury-indexed ARMs averaged 4.58 percent, with an average 0.5 point, down from 4.64 percent last week and 5.03 percent a year ago.

Those rates are for borrowers with an 80 percent or lower loan-to-value ratio on loans eligible for purchase by Freddie Mac. Borrowers making smaller downpayments or seeking loans too large or risky for Freddie Mac can expect to pay more.