11/18/2014 12:11 PM
I've probably have done it a dozen times or so by now. It's not a lot of fun but what works best is to have someone try to listen and watch for the heads as the heads are blowing out. Run the heads whatever way you choose and have someone walk the line to each head. They will be able to tell if the head is blowing air, water, or neither. Most of the time it pretty obvious even from a distance.
The more difficult part is trying to find the q.c.'s buried in snow. That's why we stake everything and color code the stakes to tell us if it is a valve, q.c., air relief, etc. We do this a few weeks before blowing out just in case we wind up in a situation like you are in now. A metal detector will help but its still a slow process.
It's really not anything to worry about though. You'll get it done.