How to extend a CO?

I have a 45-deg Wye with a CO glued on at bottom of a drop.... problem is a new wall was added behind CO that makes access difficult. What I want to do now is extend the CO back to the face of the wall so access will be from other side of the wall. Can I do this simply by screwing in a male threaded adapter into the CO and gluing pipe and new CO onto that?

If that will do what you want, the yes, assuming it is NOT a 3 1/2" cast iron cleanout.

You will want to make sure that you use long turn radius fittings for any extension. Make sure also that the clean out at your final finished wall isn't tighter than the one that is buried.

hj said:

If that will do what you want, the yes, assuming it is NOT a 3 1/2" cast iron cleanout.

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No, but I do have another 3.5" CI CO elsewhere... I thought my building sewer CI pipe was 3" ... but I measured the floor CO to 3.5" as you suggest... does that mean my building sewer is really 3.5" or 4" or what? I sized my vents assuming it was 3"! Am I in trouble?!?

DavidTu said:

No, but I do have another 3.5" CI CO elsewhere... I thought my building sewer CI pipe was 3" ... but I measured the floor CO to 3.5" as you suggest... does that mean my building sewer is really 3.5" or 4" or what? I sized my vents assuming it was 3"! Am I in trouble?!?

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Your building sewer can be either 3or 4in., the c.o.s were made in off breed sizes to stop people from attaching pipe to them