Sewer Main to Street has poor slope and bellies

[scottk123]

Hello All,

Our house was build in the 1950s or 60s, but was remodeled 17 years ago (at the time of the remodel, the sewage was completely redone up to the property line cleanout). The contractor used black ABS pipe. See my picture to give an idea of the house sewage system. There are two sewage lines coming from the house and one coming from the guest house. They all joint together into one line that goes out into the street. Overall, the sewage is traveling about 260 feet from the house to the manhole in the street.

Our plumbing does work (meaning toilets do flush, and sinks drain) but it gets clogged/backs up a few times a year. Sometimes, when it backs up, sewage comes out of our shower in the guest house (lowest point).

As you can see in the picture, we have bellies at the end of the driveway near the street (cameras go underwater and water/material is not flowing) and we have a belly closer to the house (camera goes underwater here but the water looks to still be flowing).

Some contractors told us we need to replace all the pipe from the clean out in the driveway to the manhole in the street. Others said it needs to be redone all the way from the house to the manhole in the street.
My fear is that even with all new sewer lines from the house to the street using a rigid pipe like C900 to prevent sags, we still wouldn't be able to get enough slope in the pipe to make a significant difference over out current plumbing.

The other option (instead of new sewer lines) would be calling a service to hydroblast 2 times a year or whenever it starts to back up just to keep the lines cleared.

 

[scottk123]

Regarding slope, the our pipe drains into the manhole and is about 8 feet deep at that point, at near out front door, it is about 3.5 feet deep at the front of the house. So it drops about 4.5 feet over the 260 feet.

 

[Chris]

That's sounds like almost 2% fall which is good if the ground is perfectly level on top. Usually we use a laser to check level of sewer pipe. A system can work fine with 1% fall if installed correctly. You might want to check with your city, town ,sewer district to see if they own the part from the manhole to your property line. Usually they do. It is also possible to just dig up and replace the section with the belly. Shouldn't have to replace the entire line.

 

[pasadena_commut]

but was remodeled 17 years ago (at the time of the remodel, the sewage was completely redone up to the property line cleanout). The contractor used black ABS pipe. See my picture to give an idea of the house sewage system.

As you can see in the picture, we have bellies at the end of the driveway near the street (cameras go underwater and water/material is not flowing) and we have a belly closer to the house (camera goes underwater here but the water looks to still be flowing).

Is there some reason that those particular regions would sag? Nearby trees? Some sort of drainage feature? (Like a low point on the property and/or a pond or stream of some sort.) Is this in a region prone to collapse, like parts of Florida?

One would hope that when the contractor installed it originally there were no low points like that. Since there are now, and the pipe wouldn't move by itself, that suggests soil movement, which in turn suggests moving water outside the pipe. A leaky drainage (or other) pipe could cause that but as suggested above, purely external factors may be involved. In any case, you really want to know why the pipe moved because otherwise after it is dug up and replaced (just the bad sections, why replace sections which are not having issues???) the problem could return in another 10 years.

 

[journeyman]

Yes abs is a foam core pipe it bows easy. It is a terrible product due to the flexibility. I strictly use box because it is a stronger pipe. Whoever put pipe in either put a bowed piece of pipe in or it was not compacted properly see it all the time. Abs is junk pipe

 

[Chris]

Yes abs is a foam core pipe it bows easy. It is a terrible product due to the flexibility. I strictly use box because it is a stronger pipe. Whoever put pipe in either put a bowed piece of pipe in or it was not compacted properly see it all the time. Abs is junk pipe

Don't forget it could be a poorly graded trench too. or dug too deep then fluffed dirt in to get grade then when compacting it pushed it all down.

 

[journeyman]

Your absolutely right chris but I don't know how many supply shops I go to and all the abs on racks is bowed. If he has 2 percent grade then it almost sounds like a belly. Only a camera would be able to see