It will be interesting to see "how" he does it. If he doesn't want to wreck the concrete he first has to find a way to cut the pipe below the present concrete level from the inside of the pipe. It can be done using some ingenuity, but not easy. Any fitting he then puts on the pipe will be larger than the exterior of the pipe so he would have to chip away at the concrete a little. He might be able to use a 4" x 3" bushing and then a 3" adapter and plug. This would be smaller than the present hole. He would then have to fill in around it. I'm not positive if going down from 4" to 3" for a clean out meets code or not.
In short, if he's ingenious he might come up with something that's pretty acceptable, but it's going to take some work.

---contractor says he'll put a fitting in the pipe---

If this is correct, in the pipe, then I see a 15 minute job without chiseling.

Rough cut the pipe, dremel type tool on the inside of the pipe for final cut, glue in fitting and hold for one minute, screw in cap, slap on metal cover, done.

As hendricus says,

An inside pvc cutter or dremel will suffice and an insert pvc c/o body and brass/metal cover. Some can be screwed in and others sit in body against gasket and held with 2 screws.

With the deck concrete at 4" thickness the dremel tool fianal cut will have to be at a level below the concrete in order for the c/o fitting and then the metal cover to fit flush with the decks surface. Will this really be possible to do? Tom

yes yes yes

You're cutting on the INSIDE of the pipe, you can go as deep as you can reach.

That's the process I was thinking that he could use also. To get really picky the question I had was is there a problem with code using a 3" plug in a 4" line which is what he would have to do. I mean I wouldn't hesitate to do it at my own house, but would it meet code?

Since the cleanout is outside the house the building department doesn't look at it. It's under the health dpt and they really don't have any specs. A 3" c/o in the 4" line will be approved. Thanks, Tom

Happened to be looking for something else but, here is what we are talking about-

Here is a link that might be useful: 4

Quote:"Since the cleanout is outside the house the building department doesn't look at it. It's under the health dpt and they really don't have any specs. A 3" c/o in the 4" line will be approved. Thanks, Tom"

WRONG!

Although your Plumbing Inspector works out of the building department, the entire Plumbing Code is a health code and the Plumbing Inspector is in fact a health official. It should also be noted that in most jurisdictions the Plumbing Inspector has full arrest powers and he/she can pull your certificate of occupancy and order you to leave the structure immediately pending a court hearing.

Now in regards to the size of a cleanout on a 4" house sewer line. Both the International Residential Code and the Uniform Plumbing Code permit a 3.5" cleanout.

Ref:
IRC-3005.2
UPC-707