The new and old systems should be tied together in two places, at the top for venting and at the bottom for draining. Before cutting, acquire several Mission transition no-hub shielded couplings. The coupling is a thick rubber tube with a metal fastener (this also serves as the shield). It is used to connect a metal pipe to a plastic tee.
Besides their material practicality, these plumbing parts have a psychological use. Whenever your wife asks why the plumbing is taking so long to finish, simply mention "Mission transition no-hub shielded couplings". You don't even need to go into detail, the mere sound of the words will cause her eyes to glaze over, or, at least, impress her into believing you know what you are doing. She will imagine that there are unfathomable difficulties inherent in your work.
"Mission transition..." is one of those technical terms that can make you look more intelligent than you are. Handy words for other stages of construction include: ground fault interrupter, polypropylene and henway.
To interconnect the vent pipe, it will be necessary to make another excursion into the attic. You will want to make the first two cuts in the old stack near the roof line.
In my attic, I keep two small boards to facilitate movement across the joists. On the occasion of cutting into my stack, I laid down one, crawled on it, then laid down the other, alternating them until I reached my destination.
As usual, it was hot in the attic. Before I had even reached the stack, sweat was dripping from my brow, and fiberglass stuck to every appendage of my body that was not clothed.
Avoiding the roofing nails that were coming through the sheathing above, I positioned myself near the stack. I sat on one of the boards, and propped my feet against a joist. Grunting and groaning, I wrapped the chain around the stack. Moving it back and forth, I could hear the wheels cut minutely into the pipe. I soon fell into a rhythm. I could have used the same motion to row a boat. At every stroke, my head poked between two rafters and came perilously close to where roofing nails jutted out at me like so many spikes in Ty Cobb's cleats (only they were not aimed at my ankles).
I stroked and tightened, stroked and tightened, until I was bathed in sweat and heartily sick of rowing and going nowhere. I removed the chain and found I had barely
scraped the surface of the cast iron. When I replaced the chain, I screwed it down with a pair of pliers to get the deepest possible cut. Then I again pushed on the rowing handle. Only I had tightened the chain too much. To get the rowing motion started, I leaned all my strength into the handle.
As in every other time I have hurt myself, I had a presentiment of what was to come. It was not a psychic thing. It was my latent common sense manifesting itself just as I felt the cutter wheels giving way. I flew forward in a headlong rush to meet the sharpest, meanest roofing nail ever to poke through a piece of sheathing.
"Arrrghgh!" I shouted.
The nail momentarily blocked my rational thought process by stabbing the top of my head; I believe it squeezed between my frontal lobe and the medulla oblongata. Fortunately, my reflexes were still intact; I quickly pulled back from the nail.
No distinct word passed my lips for over a minute. I pressed both my hands against my head as if that would squash the pain. I considered for a moment I might also be preventing some gray matter from seeping through the hole made by the nail.
When the synapses in my brain finally restored some semblance of logical thought, I looked at my hands. They were wet, red and sticky. I only vaguely wondered at the seriousness of my injury; for I was now faced with a serious dilemma, the same dilemma I had confronted last time I was in the attic. I could take the long arduous trek back to the attic access, climb down to the bathroom, deal with the wound, then crawl back to finish the job, or I could stay and row the cutter until I collapsed from loss of blood and fainted with exhaustion. A rational being would have taken the first choice, but two factors motivated me to stay: 1) I was angry enough to slice through the pipe with my bare hands; and 2) The clock was running on the pipe cutter. I had rented it by the hour.
I gripped the handle with my bloody hands and went to work with a will. I found that tightening the wheels with pliers had succeeded in making a quicker cut. I only had to be careful about applying force to the handle. With my painfully acquired knowledge, I made short work of the two cuts.
Dragging my tools behind me and keeping my head low, I slowly crawled out of the attic and trudged into the home hospital. In the bathroom, a vague smell permeated the air; I thought it might be the smell of my mingled blood, sweat and tears. I also was subjected to an image far more frightening than any I had ever seen in a horror movie. It was my own face streaked by dried blood and hair matted with the sticky stuff. I hastily wiped my face. The blood in my hair proved stubborn, so I left it for later.
Only slightly refreshed, I slung the pipe cutter over my shoulder and went to tackle the downstairs cuts. The smell I had noticed in the bathroom had grown stronger in the laundry room. I forced myself to ignore it and fell to cutting the pipe. Given the space and time constraints, my plier technique made the job easy.
A hazy look at my watch told me that the end of the next hour on the pipe cutter rental was approaching. That pipe cutter was worth about five times more per hour than I was. There was no sense letting it sit around like an idle worker.
Without further ado, I climbed into my pickup (which was still pointing skyward from the cement load) and returned to the rental shop. The open windows in the cab seemed to dissipate the odor that had harried me inside the house.
At the rental store, I humped the cutter out of the truck and dragged it to the counter. "I'm back," I announced.
The man behind the counter looked at me closely. My matted hair and rosy cheeks gave him plenty to wonder at.
He hesitantly produced the rental agreement, passing it over the counter top. "Sign here," he said tersely, pointing at a red X.
"Sure." I tried to sign with the wrong side of the pen. It was a mistake any one could have made.
"Are you OK, Mister?" The salesman put a hand on my arm.
I nodded my head.
"Are you sure?"
I touched my wound. The bleeding had stopped. "I'm OK." He shrugged, chinged the register and returned my deposit. I stuffed the money in my shirt pocket and wandered toward the door. Before I could make my escape, the man called out, "Hey, Mister..."
I turned to see him holding the pipe cutter.
"What did you do with this thing?"
"Cut a pipe," I explained. I had made an effort to wipe down the handle. Evidently I had not removed all the blood.
He looked at the handle, then at me. I was sure he thought I had gotten into a fight and used the cutter as a weapon. "I didn't hit anyone," I said. Then again, he might have thought I had been beating myself over the head with it. It was the more likely story. "I didn't hit myself either."
"Yeah, sure," was the skeptical reply.
I stumbled through the door, thinking the nail might have done more damage than I had suspected. To this day, I marvel that I not only drove home without mishap, but that I never got a visit from the police as a result of that episode.