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low spot in sewer line causing toilet backup?

Posted by laff66 (My Page) on
Fri, Jul 13, 07 at 16:01

We moved into a 30+ year old house in February and have been having intermittent toilet problems ever since. On two occasions we've had a sewer line backup that were opened up by a powered auger. It seems like the two problems are related, but now I'm not so sure. On and off the master bath toilet just refuses to flush completely about once every ten flushes. Plumbers were just here, pulled the toilet and ran a camera down the line. There was one point where the camera was completely underwater for several feet. They decided it meant that there was a low spot, and said that was causing the problems. There was still quite a bit of open space in the pipe but there was quite a bit of buildup on the lower half it, similar to what barnacles on a boat hull look like so I'm guessing its been that way for a LONG time. The fix was to tear up and re-install new sewer line with more fall to it. Is this a "must-do" repair, or is this a fairly normal condition that a lot of older homes have?

Follow-Up Postings:

RE: low spot in sewer line causing toilet backup?

All houses of your vintage had terracotta/clay pipes etc and will all eventually need to be repaired or replaced. The sooner u get on top of this the better. There are new systems to reline the pipe but will only be useful if the pipe is beyond repair. It sounds like you probably have tree roots that have infiltrated the pipe (due you have tree?). Basically what happens is a new pipe is placed into the old pipe using a felt core(bag) and then adhered to the old pipe which in turn increased the flow and if you use the correct lining system, then leakage will be eliminated. This system can save you thousands of dollars compared to replacing the pipes as there is no or very minimal digging required. I have suggest a website you may want to check out for just google blocked drains or pipe lining or unblock pipes etc or streamlinedrains&pipes.

RE: low spot in sewer line causing toilet backup?

We actually have cast iron pipes. There did not appear to be any roots on the camera, as we got a very clear picture all the way through. Its just that at one point the camera "eye" was underwater for a while, where it should not have been.

RE: low spot in sewer line causing toilet backup?

relining will not solve a dip in the line, the grade must be corrected. Based on your description there is a section with inadequate flow, this will allow solid and sludge to settle in that area. Also you say "it looked like there was still open space, but sewer lines are sized so the pipe is never completely full of water, something like only 1/3 of the pipe is supposed to be filled with water.

RE: low spot in sewer line causing toilet backup?

"All houses of your vintage had terracotta/clay pipes etc and will all eventually need to be repaired or replaced."


The post says the house is 30+ years old. Both PVC & ABS pipe have been available and in common use for 50 years. In addition, there was concrete hub&spigot SV pipe, Borosilicate glass pipe, vitreous clay pipe and orangeburg pipe.

The post also says the problem is a low point in the pipe where water is colleting.

That standing water causes two very distinct problems.
1. It creates a trap between the house and the sewer which prevents the movement of vent air.
2. The standing water creates a barrier which restricts the velocity of flow which then causes solid particulates in the waste water to settle and collect forming clogs.

Neither of these conditions would be remedied by religning the pipe as was suggested by Alexbar001.

RE: low spot in sewer line causing toilet backup?

Cast iron was still in use well into the 1970s, though with rubber 'donut' seals between sections.

The plumber should be able to tell you the approximate location of the dip.
It needs to be excavated and repaired.
Be aware that if the pipe leaked at the joints the repair area can be larger than just the dip.
Fill should be gravel under the pipe and gravel above.
The more gravel the less subsistence when the trench is refilled.

RE: low spot in sewer line causing toilet backup?

Correct, re-lining would not do us any good, as there does not appear to be a leak or a break. If anyone has had a similar problem repaired, were they able to "spot" fix it, or did you have to have a long section of pipe replaced. I know it depends on a lot of things, I'm just curious. The plumbing company also mentioned boring under the house and running a new line out to the sewer line. That sounds much less invasive, but I'd be worried about hitting two other drain lines that should be in the same area.

RE: low spot in sewer line causing toilet backup?

hello tim got a problem haveing sewer gases smell all over
the church building. I am a church janitor for 22 years we
have tryed many such as spray, water hose, fan. I think we
have a low spot in the line or we could need some roof vent. so air can get line. what can we do .

RE: low spot in sewer line causing toilet backup?

Less than 30 days ago a plumber unclogged the toilet with the claim that a plastic toy was the cause.Even after this was done the water slowly drained.Now no longer does a plunger help and there is a standstill.With only one toilet are there any quick fixes to this 30 yr unit ?

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