I'm replacing my cast iron stack with PVC and have a question about the toilet drain/bend. When the house was built, the cast iron stack came up from the basement, cut diagonally across a joist, picked up the 2nd floor toilet, then continued vertically to the roof. Using the PVC pipe and fittings, the height of the new flange will sit a half inch or more above the finished floor. I have tried every combination of 4" and 3", all degrees, etc., and can't find anything that will leave me flush. I could lower everything by cutting further into the joist, but as it is, when they built everything they cut about 6" out of the 10" board. The closest I can get to flush is with a 90 degree elbow. I believe its a vent elbow. (no sweep, female fittings on both ends, no visible hubs). But I'd have to cut off about a 5/8" from one end. Is that acceptable? Thanks.

I am completely cahnging all the plumbing in the house I recently purchased , there was no maintenence and every vale leaks . I will be using Pex like the last house I had , and I would like to install a loop systym as I have seen on Holmes On Holmes . It consists of a main loop , with take off valves for the individual lines , and it's fed on either side by the main hot/cold line , so there is no loss of pressure when faucets are opened , and it's all in one spot to shut off and isolate each line . What is the technical name for this systym ? many thanks , jim