My kid bought a 1958 ranch on a slab in Framingham, MA. Now the main drain seems clogged, with whatever goes down coming up in the tub drain which is the lowest drain. So I look for an indoor cleanout everywhere I can imagine but find nothing. Then he digs about 36" from the foundation in line with where I figure the main drain comes from. There are two baths back-to-back. The sink drains go towards each other and meet in a Y and a single pipe drops into the slab. Each toilet's outlet goes straight back. So I figure the main picks up the sinks and then has a 4' double Y or a cross to pick up the toilets and then goes outside the slab since the toilets ate against an outside wall facing the street. Well needless to say we couldn't find a pipe down there. Next step was pull a toilet and run a motorized snake down. The snake however will only go into the opposite toilet. So I pulled that toilet too. I planned to reach in and force the snake tip into the outflow pipe. But I couldn't feel anything like a cross (couldn't be a double Y with the snake going straight through). So I got a small "See-Snake" video tool. Putting the camera in from either side I see the same thing: a flat metal panel with 2 holes straight ahead; the opposite toilet line and a hole thats's blocked with metal... almost like a giant electrical knock-out. I can't see or feel a pipe from the sinks or an outlet. It's like there's a metal box around 10" x 10" x 5" in the wall. So so far I seem to not be able to snake it... plus that strange seeming junction box scares me a bit (anyone ever seen this before?). So BTW there is a kitchen sink and tub which seem as though they tie into the main ahead of the twin sinks. I'm looking for tips cause I'm running low on ideas. Meanwhile my kid's staying in our guest room. I guess next stop will be the town offices to see if they have any sewer connection location info and if outdoor cleanouts were required in 1958.

Many older homes don't have any, a lot of homes I buy ( have not bought any in MA) don't have any clean outs at all, and I have to normally add a outside one.

Of yourse you can pull the toilet and run a snake though that opening.

IF you can't find any cleanouts, and snaking from toilet drains isn't an option, you may try snaking from the roof vent. Hopefully an option for you.
Did the see snake have an option to record. If so, I would sure like to see that tape. Are these wall hung toilets, or floor mount toilets? Interesting indeed.

The see-snake has no way to record. They're floor mount toilets.

Another instance of "here, son, let me show you how easy this is".

In my area we are mandated to install a clean out no over 18" out from the foundation and bring it up to grade. ( we have slab buildings) This will usually be found on the same side of the house the street main or septic tank is located. In time the cleanout may be covered over with dirt.
Then we take a pointed rod called a Probe and poke around until we hit it. If you can' locate a cleanout then follow Lees advice and snake from a roof vent, this will get you out in the sewer. Good lock, Tom

Well, he got the town to mark the location the line joins the main. He dug along that line about 24" from the foundation and at 38" he hit the top of the pipe. No sign of a cleanout however. Next step he'll expand the hole along the pipe and hopefully find a cleanout. If not, can I buy a new hubless sanitary "Y" and insert it in the line with hubless clamps? Or can I buy a new PVC sanitary "Y" and insert it in the line with hubless clamps?

I'm with Lee, go on the roof. However, since you have the pipe exposed opening the pipe is not a bad option but try the roof first. Can we assume the drain line is cast iron and not PVC or other material? A cast iron pipe can be a buggar for a DYIer to open.

Yes, the underground line is cast iron, 4" I believe. I have an angle grinder and a bunch of cut-off blades ready. I don't know if its possible to insert a PVC fitting into a cast drain line...in other words, is the OD of a 4" cast line nearly the same as the OD of a 4" PVC DWV fitting or line?

Since the junction of the toilet lines and the line to the street are so weird I have very little faith that a snake put down the vent would go down the line to the street. And holding the Rigid snake machine on the roof would be interesting.

Thanks, Larry