I installed a garage htr several years ago and hve gotten a complaint of leakage through the venting. All others that I installed were side wall vent, This particular install was vertical through the roof. I looked at the latested install guide and see that the venting instructions now show a tee and a drip cap at the bottom of the verticle pipe. My original install was "B" vent. I don't think the IOM showed a drip T because I probably would have installed it that way 5 yrs ago when I put it in. Now that winter is here they called me and asked if I can do somthing about the leakage. In the past I/they thought it may be a roof issue so they didn't compain to me about it. I now realize that it is a condensate issue and must take care of it for them. They have been very patient about this but I know that it is my error. I do not do much install or resi work but I must make this right! I have checked with supply houses for the proper materials for this type of venting and I am having a hard time finding drip caps in the 4" size. I have seen boiler rooms that have venting with these types of caps with ball valves installed. Does any body have experience with venting these products and materials to use? Also do you simply caulk the gores?