We just bought an old stone farm house. The contractor and previous owner recently abondanded the septic field and connected the house waste to the city sewer system. He did this after we bought the property. I observed that the sewer clean out junction was not a "t" connection but a "u" shaped connection. Similar to what you see under a sink. Is this acceptable?

" I observed that the sewer clean out junction was not a "t" connection but a "u" shaped connection. Similar to what you see under a sink. Is this acceptable?"

What it sounds like is a running trap,(see image). The running trap was installed in the sewer line to prevent sewer gases from entering the house from the septic tank. Unless it impedes the flow of sewage it isn't doing any harm. A running trap will prevent backdraft from the sewer in the present configuration. Cheers, Tom