What's causing the sewer to back into the tub?

Question

We've lived in our house for several years with no sewage problems to speak of.

A few weeks ago, my wife was sick of the sinks not draining very well so she went online and learned about cleaning out the traps. She did this. Around the same time, I learned where our DWV plug is, because I thought it was a rock and ended out breaking it off trying to remove it (it was buried in the dirt).

The cap was off for several days before I learned what a DWV plug was and what it was for and bought another one.

I put the cap on, but I didn't have anything to tighten it very well.

After she cleaned the drains for the next several days occasionally we would smell sewage from our bathroom sinks. We put it down to just the traps being clean and maybe something else. Then last Friday night, my wife called me to say that sewage was coming up in the showers and leaking from the bottom of one of the toilets.

She cleaned it up, and a friend came over and pulled the DWV plug, and there was sewage up to the top of the pipe, which is about 3' deep. He had one of those accordion style plungers and plunged the DWV pipe and after only a couple of plunges the pipe cleared.

We thought that everything was OK, though today I smelled some sewage from one of the bathroom sinks. Then about an hour ago my wife got home, went inside to take care of some stuff and surprise! More sewage. I was able to pull the DWV plug and plunging had the same effect: about 20-30 plunges and the sewage drained again.

We just spent the last hour or so pulling up laminate flooring and sucking up wastewater. It's been a crappy day, let me tell you. It's really the pits. It stinks.

So what could be causing this problem with the sewage going on in our house? And better yet, how can we fix it?

Answer 1

It turns out that there was a partial blockage in our drain between the DWV and the main sewer line.

Because it was a partial blockage, some water could drain, but when there was a lot of water, and especially solids going down the drain, the line got blocked, and plunging opened a smaller hole in the blockage.

We called our water department and they brought out an inspection camera and shoved it down the drain. We couldn't tell what the blockage was, but it was right at the end of the line. They stuck this bladder thing on the end of a hose and fed it down the line, hooked the other end up to our faucet, and turned the water on. It produced a bunch of pressure and forced the block out through the main sewer line. No clue what the block actually was.