On Sat, 05 Dec 2009 09:18:55 -0500, Lawn Guy wrote:

Chris Tidio wrote:

Tired of paying to have the sprinkler lines blown out every
winter, but I also don't want to have to replace lines and
sprinkler heads in the spring :-)

I've got a 7-zone sprinkler system at a small commercial office
building. Each zone has about 6 or 7 heads. Each time the system comes
on in the summer, every head in each zone belches air for about 15
seconds before water starts shooting out of them. This doesn't just
happen the very first time the system comes on for the season - it
happens every time the system comes on.

I'm thinking that the heads or the lines have an automatic drain
function that always kicks in when the system turns off, and therefore I
don't need to blow the lines out in the fall.

Comments?

Sounds like a 'positive drain" at the end of a zone. Under pressure
the valve will close and when the water pressure is off it opens and
drains the zone of water.

Sand (pit) is used and promotes drainage at the location of the valve
(underground).