It’s hard to overstate the importance of proper due diligence when purchasing real estate. And one of the most overlooked, but important pieces of due diligence is scoping the sewer line. It only took a few thousand dollars flushed down a couple of broken sewer lines before it became clear to me that this was something that we needed to be doing.
On properties built in the last 30 years, this step can usually be skipped. However, a lot of properties, especially those built between 1940 and 1980, have sewer lines that were made out of a clay composite that has proven to wear down rather quickly (or Orangeburg which is even worse). Even if the sewer line is OK, it may need to be snaked out. The plumber scoping the line can tell you that. And it’s a lot cheaper to snake it now than the alternative of waiting for the tenants to call and yell at you for a sewer backup (which of course will happen at 11:00 on Saturday night).
A sewer inspection can cost over $200 if done by Roto-Rooter or the like, but I've found several plumbers who will scope a line for $100. And given the average cost to replace a line is between $3000 to $6000, it's well worth the cost.
Another major advantage is that a broken sewer line can be a great negotiating tool with the seller. If the sewer line is broken, go back to the seller and ask for a discount. If they won’t budge, then unless it’s still a great deal, back out, get your earnest money back and move on to the next property. For this reason, it is helpful if the plumber can record his scoping the line. But it’s not required so long as they provide a written report.
It is, however, important to be aware that there is a risk that the plumber will convince you that the line is completely shot and needs to be replaced when it simply needs to be snaked out. So make sure to go with the plumber when he scopes the line. A few roots here and there shouldn't be a problem. Just snake it out and remember to flush root killer down the drain every so often. Sizeable offsets, holes in line, large bellies or major root intrusions are the primary concerns. Indeed, it's probably a good idea to tell the plumber that you already know the company you will use to replace the line just to prevent there being a conflict of interest. Or sometimes you can find a plumber that scopes lines, but doesn’t replace them. Finding such a plumber would be even better to remove that potential problem.
Regardless, while it's important to be aware that the plumber may try to oversell the condition of the line, it's absolutely critical to know what condition that line is in. If the property is more than 30 years old, make sure that scoping the sewer line is part of your due diligence.