I had freeze damage on a section of main line at this apartment complex I take care of. I've blown out the system the last two winters and this is the first time with damage. Anyway, I dug up the area today and found that they ran this section of the main down hill and then just capped it at the bottom of the hill. So, this section never gets blown out and the entire section is above the frost line. Why did it break this winter? This system is pretty old and has gone through many a winter. Can PVC handle a number of freeze/thaw cycles before cracking?