Grounding Rod Through Main Sewage Line - Who Pays?

Location: Connecticut

Over the course of the three years we've lived in our home, our basement has flooded due to the main sewage line becoming blocked. As new homeowners, we assumed there was a fault in the line that we'd have to fix down the road, but the professionals we hired to clear the line suspected it was a fault in the pipe itself. We were advised to save up, because at some point in the future we'd need to dig up our front yard and replace the line completely.

We installed solar panels just a few months ago. As part of the installation, the installer put in new grounding rods. Several days after this, our basement flooded. We had a professional run a camera down the line, at which point he discovered a copper grounding rod rammed straight through the main line (clay). The video, which we recorded, showed water continuously flowing down through the break rather than out the main line to the sewer.

Assuming it was our solar installers' fault, we contacted them with pictures and video, and they came right out to remove the rod. They removed the rods they installed, but none had pierced the main line. they did locate the rod driven through the main line, but upon closer inspection the rod was dated back to 2011, and we were able to locate a building permit which shows an electrician performed a service upgrade at that time. In short, our solar installer did not ruin our main line, but our basement has been intermittently flooding for the past fourteen years due to work that was done in 2011.

Since then, we've taken the following steps:

1. Reached out to our insurance. We could put in a claim, but our rates will likely rise and our insurer seems unconcerned about the state of our foundation. Our fear is that we will put in a claim, then find out down the road that fourteen years' worth of water flooding our foundation has caused even more damage than we currently see. Our other fear is that the cost of the eventual work required will exceed the 10,000 backup coverage we have.

2. We reached out to the town because records show that they inspected the installation and passed it. We asked how it passed given there was an electric rod driven through the main line. They said they don't check for that, and suggested it was the electrician's responsibility.

3. We reached out to the individual electrician who completed the work and asked for his insurance information. He said he would talk to them and get back to us. Naturally, that's the last we ever heard of him.

We're at a loss as to how we should proceed. We have photos and videos of the rod where it pierces the mainline as well as of the date on the rod. Of course, we also have town records clearly indicating the electrician by name.

Is there any legal route forward? If so, what would it entail?