What can cause a blockage in an otherwise decent main sewer pipe?

Question

I purchased my first house (on city water and sewage system) about 6 months ago and the main sewer drain clogged and backed up through the basement drain within the first week being there. We're talking a couple of showers and some typical toilet use. Plumber used a rooter to clean it and I haven't had a problem since. He showed me using the camera a small dip in the cast iron pipe where he believes the clog was, but other than the pipes being old (house 1963) he says they still have life left. No roots found, and I believe he checked all the way to the end of the pipe (to the street).

My question is: why did they clog for me and not for the previous owners of 30 years (assuming they are being truthful and also based on the rusted shut clean-out access point). Not knowing if/when the pipe is going to back up again still keeps me up at night.

Possible reasons I could come up with:

• The house was sitting unused (how long I am not sure, 1 week if I had to guess) which gave time for gunk to solidify in the slight dip
• Something crawled up the sewer and died in the slight dip
• I introduced something large enough to block the sewer, but I am very aware of what I would put down the drain

The blockage was in a section of the pipe still under the house, maybe 20ft from the clean out access point.

Any thoughts whatsoever appreciated.

Answer 1

I'm not saying this happened, but in my experience previous owners tend to say: "Gee, my basement never leaked," "Gee, my roof never leaked," and on, and on, and on. You did the right thing by having your sewer line cleaned and checked professionally. If the blockage becomes an ongoing issue at the dip, you may decide to have it dug up and that portion replaced, or perhaps the entire line. Camera inspections are extremely valuable for finding problems and determining solutions. I've known many who have their sewer lines rodded yearly (or so) in order to preclude problems.

Retired Contractor

Answer 2

You have a camera view and a Plummer that says the pipes are good . In this case "shit happens" the drains can be fine for years then you do some cleaning and a hair ball runs into a feminine hygiene product and the drain clogs. Since the Plummer is not trying to get you to replace the cast I would not worry because of the case I have listed seamed to happen with rentals after cleaning and new tenants.

Answer 3

Are you using so called 'flushable' wipes? Because in reality you should never flush those things down the drain, it's probably the most common thing to clog drains behind turkey drippings, and improperly discarded tampons/maxis.

Answer 4

I've worked on several old clay tile drain lines (mine and friends' using high-end HO tools - drum auger & pipe cam - for homes 90-130 yrs). The tiles develop leaks at joints and occasionally crack elsewhere, allowing roots to grow in. Finding water, they proliferate and grown into a screen which catches stuff and clogs the line. I've cleared most of the roots with a cutter blade and then used a foaming root killer overnight. The foam bathes the roots coming in from the top, and is best applied right after cutting and then annually in the Spring - times when they are most vulnerable. (I chose a non-systemic root killer because I like trees.) You may have a rust hole in the cast iron or a loose joint. It could be hard to spot with a camera.
Too bad your plumber didn't start the clean-out with the spring screw. It screws into the blockage, then you pull it back and see what you've got: hygiene products, roots, clay, pieces of tile. That could have provided a pretty good indication of the cause and potential for repetition. Two other notes from my experience: if water backs up into the basement and there's rain coming, disconnect your downspouts outside and divert the water away from the house until you get the drain cleared. And be clear with the plumber that you want the drain cleared - all the roots cut away. The biggest franchise for drain problems just pokes a little hole in the clog and gets the water flowing. It can still back up with a heavy rain, and eventually clogs up again.