Frost Proof Draining Check Valve

[John Johnson]

I'm installing an above ground 1000 gl water storage tank. To prevent freezing of the exposed supply line running to the top of the tank, I'd like to install an underground check valve which also acts like a Frost Free Valve. The idea is for this check valve to allow the water to drain from the vertical supply line when water is not flowing into the tank. When water does flow, the check valve would prevent the water from going out the frost free drain port.

Anyone ever hear of a valve like this?

Thank you in advance for your advise.

JohnJ