Our kitchen drain pipe became clogged below the basement floor on Thanksgiving. Aside from the inconvenience factor, this would usually not be a big deal. It would involve opening the cleanout and running a snake or auger down to the blocked section of pipe and working it until the pipe was cleared. Unfortunately, whoever ran the most recent drain line from our kitchen sink to the basement ran a continuous pipe to the floor and didn't bother to add a cleanout. This was crazy because the kitchen drain line is only 2" pipe - a size that is very prone to clogging, especially if any food scraps accidentally make their way down the sink. The drain line feeds into 2" cast iron pipe beneath the basement floor. This pipe eventually feeds into a larger sewer line going out the back of the house.
The clog was caused by the gradual buildup of scraps slipping down the drain. A piece of onion skin here, a stray chunk of celery there, you get the idea. We keep a strainer basket in the drain, but it seems like there's always something that manages to slip down. These wayward scraps collected in a trap beneath the basement floor until they completely blocked the pipe.
The drain line in the basement was 2" PVC pipe and looked to have been replaced sometime within the last decade. It was coupled to a very short piece of 2" cast iron pipe on the floor using a rubber coupling. The cast iron pipe was too short for the rubber coupling and a slow leak had formed at the floor. The first thing we did was remove the length of PVC pipe.
Here is what we started with. The broken piece of cast iron pipe sticking up out of the hub in the floor is way too short to have had another pipe attached with a rubber coupling. Evidence of the leak can be seen on the floor surrounding the hub. The light gray ring between the hub and the inner pipe is lead. When sections of cast iron pipe were joined, plumbers packed oakum in the bottom of the hub. Molten lead was then poured into the hub on top of the oakum, joining the two pieces of pipe together. To properly join a piece of PVC pipe to a hub in a floor like this, the inner pipe needs to be removed.
The first thing we did was pack the pipe opening with a rag to catch falling debris and prevent anything from falling down into the pipe and causing us even more trouble than we had already endured. We then used a hammer and chisel to break up the inner pipe to where it was level with the top of the hub. We made sure to have the Shop Vac on hand for frequent collection of debris.
The next step was to get the old lead out. The easiest way to do this is to drill several holes in the lead as pictured above.
We then used a screwdriver to pry the lead out. As we expected, there was a layer of oakum under the lead. We pried this out with the screwdriver as well. Again, the vacuum was used frequently throughout this process.
Once the lead and oakum were removed, this is what we were left with. Note the concrete outside the top quadrant of the hub that has eroded away due to the leak. We patched this with some cement while the hub was open.
There are two ways we could have fixed this. One way was to insert a piece of 2" PVC pipe, re-pack the joint with new oakum, and then epoxy the new pipe in place. The other way was to skip the oakum and epoxy and insert a rubber "donut" fitting in the hub and insert the 2" PVC pipe into the donut.
A donut is designed to be inserted into a cast iron pipe hub. It basically does the same job as oakum and lead - it holds the pipe inside the hub. A donut should fit snugly into a cast iron hub, but that is not always the case. This donut fit into our hub, but it could be pulled back out with a little work. To help make the joint more secure, we used some silicone on the outer walls of the donut to help hold it in the hub. Once the silicone had dried, we inserted a 12" length of 2" PVC pipe into the donut.
The next step was to add a cleanout so all this can be avoided if the drain were to ever clog again. We placed a wye fitting about a foot above the floor, then tied the line into the kitchen drain using a rubber coupling.
And here's the finished product!
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