Hi... I'm from Colorado and helping my family add on an addition to a small Orange County Beach City home. Code issues have me somewhat confussed. The BO (building official) is not too forthcoming with any explanations... he may not be too well versed in the intricacies himself and is somewhat..."Do it my/this way." Obviously, I don't want to press him or get on the wrong side. That's not my intent... but I would like to understand a couple of issues and don't want to make dumb mistakes.

Hopefully someone can help me understand what is correct to three questions. I have pretty thouroughly studied "Code Check Plumbing" which addresses 2006 UPC. I believe Ca is 2007 Ca Plumbing Code based on 2006 UPC.I do not have the 400 page Ca Plumbing Code book.

The existing home is a one-level one bathroom and kitchen on a 4" CI (cast iron)(hub and spigot) main. We are adding on an addition which will be upstream to the existing main with three baths (one on a first floor and two on a second level.)

Question 1 The BO asserts that my main (which he interperts to be my existing 4" main and its new extension into the addition and first floor bath) has to be 4 inch... and I can not add on just a 3 inch extension to the existing 4 inch main to serve the upstream three bathrooms. The existing DFU's are 10 on the 4" CI main. I will be adding upstream 21 DFU's total (9 on first floor and 12 on second floor). Total DFU's are under 35 and the extension and upstream DFU's are well under 35 for 3 inch service. I would like to use ABS 3 " for the extension of the main upstream into the addition. He says that all 4 bath homes require a 4 inch main, and apparently he considers my extension of the main into the additions first level to still be the main (and not just a horizontal branch on the end of the main). Is he correct??? My abbreviated code books do not specifically address or indicate this rule. 1) Why couldn't my entire main be 3" as it's under 35 DFU. If such a rule is written somewhere that 4 baths require a 4 inch main regardless of DFU's, can't an upstreaqm part of the main be smaller at three inches when it is serving only 21 DFU's at max. And lastly, why isn't my extension of the main just a branch, even if it is at the same horizontal level of my existing main. As a branch, it could be 3". Thanks for any education or help on this. The BO read something that said 4 baths required a 4' main, but I did not get a copy nor did he want to give any explanation.

Second Question: My code check book references a Vertical Wet Venting section, a Horizontal Wet Venting section, and then a Combination Waste and Vent section. Under UPC, it states a design for Horizontal Wet Venting that applies only to a 1 or2 bath groups on same level(all fixtures in baths including WC's) and sizes the horizontal wet vent per DFU and table 13 that indicates a 3' horizontal wet vent is allowed specifically for one or two bathrooms applications. BO says I (he) don't want that and I would have to go up two sizes in pipe to 6 inch pipe, and that I should just vent each fixture individually. My research indicates that this relatively new rule for two bath wet venting was put in for builders convenience (not inconvenience). However, then the code check book addresses a section called Combination Waste and Vent. This section says CWV requires approval from BO and addresses seemingly entirely different circumstances than the "two bathroom only horizontal wet vent" section. For instance it states no WC's and other different fixtures (than specifically provided for in the other section), requires traps and waste pipe upsizeing, and seems to address specifically designed/engeneered systems.

My question: Is the UPC Combination Waste and Vent Systems Section further limiting and qualifying their Bathrooms Horizontal Wet Venting Section, or is it an entirely different or individually designed/ engineered system. Is the BO official correct that the Horizontal wet venting bathroom design requires upsizing of wet pipe, or is Table thirteen and 3 inch fine as my book indicates. What's going on here.????

Third question: Would you have any recomendation of the best way to connect 4" ABS (or 3 inch if I were allowed as the first question asks,) to 4" CI hub and spigot. I cant's cut off the hub and just use a Fernco on un-hubbed pipe because the end connection is in a combo in the main vent stack which I can't tear into and break apart. Will Fernco make a donut type bushing that 4 ABS will fit into a 4' CI hub. If so, any idea where to find one or any other ideas/recommendations.

THANKS for any help. By the way, I want to do it right and to code. If it's questionable on these issues, I'll do it the long and more expensive way that he is ordering. I want/need to be coopertive, but I really would like to understand it. (He also says I can vent the WC conventionally with 1.5. My book indicates UPC minium is 2". He also says that I can drill studs and top plate on bearing walls at 25% and non bearing at 40%. My book indicates respectively 40% and 60%. ????

By the way, I have read and tried to research this on the internet, and everyone on here has shown their best to help others. I applaud you all. Additionallly I am hopefull lazypup is listening and could assist. He really does understand and explains so damn well the issues, I just want to say that rarely have I ever seen such good advice and knowledge... but I doubt he is lazypup... probably more like smartdog or hardworking dog.

Thank You... Peter