I have freeze proof yard hydrants in an RV Park application. Of course they are only freeze proof when they are turned off and the water drains out of the riser. During freezing weather I can keep the above-ground portion from freezing when an RV is hooked up to it by using heat tape and insulation. All heat tape I have seen is not for use under ground. How can I protect the portion of the riser that is below ground from freezing when there is frost in the ground and I have long term guests that need to stay hooked up to the water? They also use heat tape and insulation on their hoses so the only vulnerable spot is the underground portion of the riser. I am getting ready to add a new section of sites. Is there anything I can do to insulate the new hydrants when I install them?