I need some advice - my boiler setup right now has a Taco Vortech air seperator with it's stock hy-vent built in and a small bladder hydronic expansion tank hanging off the bottom. I haven't hooked up my storage but plan to do so this fall. I'm installing two 1000 gal vertical LP tanks and directly above the boiler room on the mezzanine I'll be putting a vertical 250 gal LP tank to act as my expansion tank. Originally I planned to connect the bottom of the expansion with a 1/2" pex to about any random spot in the system thinking it didn't matter. n reading the instructions for the Vortech though, I see it says "If using a plain steel expansion tank, you can direct connect a 3/4" line to the top ( in place of the Hy-Vent ). The pitch up to the tank can not be less than 1" in 5' and not exceed 7 feet total length. if the distance is more than 7 feet, increase pipe size to 1" " What advantage would there be to connect my expansion tank in place of the vent, and why would they ask for such large dia lines? It will take hours to bring my storage from 110* to 190* - a 1/2" pipe should be plenty to accomodate the movement of 100 gal of water into the expansion tank in that time.