we are having a problem with clogged pipes in the master bath area and were told to try flush them out from the outside pipe (I don't know the vocabulary for it) that we would find in the atrium. We even checked with a neighbor who has a similar house plan and found that the pipe is in the ground near the water faucet. But we don't have anything like that in our atrium. There is the original cement slab with open space along the windows and solid walls. If I can't find the pipe opening in the open space, could it possibly be under the slab?
There will be a clean out somewhere. In my atrium model, there is one on the side of the house (near the ground) close to our master bedroom. There may be a second one too. My second clean out was found in the front flower bed about 3 feet from the front of the house under a concrete top. Of course there are two large birch trees on either side of this which are always causing problems.
A plumber can also go onto your roof and clean the system via the roof vent. Of course this is much smaller and they can't clean it out nearly as well, but at least it could help out. Going up on the roof is an extra charge. I think I've had the system cleaned out via all three over the various years of residence here.