Sump Pump Discharge - freeze protection

I have a sump pump discharging through a 1 1/2" PVC line to a drainage swail, about 80' run. I have a check valve installed immediately after the pump to prevent the line from siphoning back into the well at the end of the pump cycle. To prevent freezing (we are in upstate New York) I have had to drill a 1/8" hole at the top of the discharge line to break the vacuum and allow the line to drain after each pump cycle. Although this works well, indicating the drainage line has proper pitch, it is a problem in that the small amount of water that comes out of the 1/8" hole, over a period of several days in sub freezing weather, forms enough ice to start to block the hole.

I am thinking that what is needed is some sort of a vacuum relief valve, installed on the inside of the house to avoid freeze up issues, to break the vacuum and allow the line to drain. I have been to several local plumbing supply houses, and they have been of no assistance. Any thoughts other than replacing the 1 1/2 line with a 3 or 4 inch line and letting the 1 1/2 dishcarge line break vacuum where the two lines meet?

On an irrigation system that is pumping out of a 10,000 storage tank, unless I break the vacuum after the pump cycle it will siphon the tanks dry.

I use a spring loaded check valve above the siphon level of the tank, when the pump turns off, the check valve lets air in to break the siphon effect.

Rancher

One of the products I've seen around here is called "IceGuard" and is made by Basement Systems. It's basically just an opening between the discharge pipe and a larger drain pipe placed immediately outside the house. You could probably come up with your own version pretty easily if you can't locate a dealer/distributer in your area (or if you are cheap like me!).

Here's some info from the manufacturer:
http://www.basementsystems.com/basem..._discharge.php