Sewer line camera inspection and repair

[Curt Bixel]

Just sat with a service tech from a plumbing company and watched the video from the camera they pushed down the sewer line in a 4 family property.  It is a 4 inch pipe, and there seemed to be a fair amount of what they called scale.  The bottom quarter of the pipe is mostly filled with scale with a small trench running down the middle.  The full length of the pipe they said needs to be addressed is about 60 feet.  

The suggestion was to clean it with a combination of hydrojetting and some sort of spinning chains with carbide tips to break down the scale.  They will need to dig a 8 foot by 4 foot trench just in front of the house to a point in the line 9 feet below the surface, and unfortunately, under the sidewalk and front stoop of one of the units.  

The estimate for the hydrojetting and spinning chain treatment is about $10,000, and if the line ends up being replaced, the estimate was between $30,000 and $40,000.  

I curious if this seems like a normal cost for this service and what other options their might be.  The line most definitely has a problem with clogging every few years.