I purchased a house two years ago that had a complete basement renovation 5 years ago. Basement plumbing includes a 3 piece bathroom (shower, sink, toilet), a bar sink, a laundry room sink, and a drain for the washing machine.

About a year ago, the toilet began clogging. I tried unclogging it for several weeks with limited success. Called in a plumber who after three nights of investigation told me that the basement toilet had been inadvertently hooked up to an old septic tank and it would cost $7000 to properly connect it to the main sewer line. I choked on the price and decided to live without a basement toilet for a while.

This summer I tried to look further into what would be required to get the toilet working. Had a plumber in for a quote, and he suggested I get the septic tank pumped, and that might be a cheap solution to my problem. The problem is I couldn't find the septic tank (the tanks were disconnected in 1958, so there are no records as to where they're located on the property).

To aid in my septic tank search, I had another plumber come in to do a locate with the cable snake. He could not get the snake out of the house, and is questioning whether the original septic tank diagnosis was even accurate. He suspects there is a sewage basin under the floor in the laundry room. He provided me with a quote of $1400 to crack open the laundry room floor and find out exactly what is going on.

Before I start cracking tile, I'm going to do some more digging outside to see if there's a pipe coming out of the foundation outside the laundry room.

Knowing virtually nothing about plumbing, all of this has been quite strange to me. However, there's an even greater mystery.

On my electrical panel, there's one switch which is turned off. When I turned it on, my basement drains immediately started to back up. The assumption is that there is a sewage ejector pump in the basin which starts pushing water backwards up the drains since its outlet is blocked (either by a full septic tank, or a sewage basin clog, depending on who you talk to). The mystery is that all the drains in the basement work perfectly fine. All of the plumbers and contractors I've discussed this with are stumped.

Could there be two outlets from the basin - an unblocked one for wastewater, and a blocked one for sewage?

If anyone can shed any light on any aspect of my mysterious basement plumbing, I'd appreciate it.