SD2. I am out here in Northern Colorado and we use anti freeze wherever we can. I agree that in most large scale situations a dry system can reduce the cost (especially with a listed tank)but we have found ways around that. All of the AHJ's in our area have accepted figure 7.6.3.1 with a loop and the 1/32 hole check valve without the tank. The reason being that the wet system it's attached to will act as the expansion chamber. Depending on the situation (new system vs addition/Tenant improvement) the upgrade from a double check to RPZ is typically cheaper than installing a dry system. We have also been known to install a small RPZ at the beginning on the anti freeze as opposed to a large RPZ at the riser.
Just as a side note. Most of the water districts in our area are accepting glycerin in the anti freeze without the addition of the RPZ as it is food grade and does not pose a threat to public health.
