Ok, I have a 4" flex pipe under my hearth floor (between joicing) going out side of house, and it is terminated at my hearth floor behind the stove, with a 4" flex pipe connector "barrel" (the kind you would use to simply attach two peices of flex pipe together). I'm not sure if I will need or use the OAK for my stove, but since the OAK pipe was already there, I worked it into my new hearth just in case. I would like to connect it to a Y type valve, that would allow me to "select" either outside air, or inside air (other side of Y). This way I can get the OAK for my stove, connect it up, and then select outside or inside air with the simple switch of the Y valve selector/damper. So where do I get a 4" Y valve pipe?