Im trying to figure out the best way to solve a problem I am having with moisture buildup in the exhaust of my high efficiency gas water heater. I am using 3" PVC and it is ducting horizontally about 70-80 feet before exiting the house. Every few weeks the water heater stops working because of the water buildup in the exhaust line and I have to take apart a joint in the line and drain the water. It is probably 2-3 gallons. I am well within the length limitations stated in my owners manual for the length of exhaust line specified at the 3" size i am using. (It says i can go up to around 160') Am I going to have to put drains in the line to stop this, or can I just put a slight angle on it so it slopes towards the outside? I could do that for part of ithe run but not all of the run. It is possible that I could exit the house another way and shorten the run about 25', it would just be a pain to do. Would shortening the run help?

Any help would be greatly appreciated.

Todd in WV.