How to Unclog a Main Sewer Line

411 plumb The first thing you have to do is find the best place to gain access to the clogged sewer line. This varies in different types of construction but the most desired location is always an outside cleanout. Other locations may be a cleanout in the basement, cleanout in a floor, via a pulled toilet, from an opened septic tank back towards the house, or in some areas going down a roof vent. You will also have to look at evidence to determine where the clog is and how to best get access to allow the snake to reach the clog. This is a decision easily reached by a Drain Cleaning Pro but is often difficult for a DIYer.

Once the location of the clog has been determined the next thing to do is select the proper drain snaking equipment to clear the clog from the line and how long it needs to be. There are a variety of machines used and the cable length they need to reach to clear the clog is important. A cable too short may not reach the clog and a cable too long if fed out too far will get tangled and knotted in a septic tank or, city sewer line. In any case the cable should be a minimum of 1/2″ diameter and that would be woefully inadequate if roots are encountered. Equipment selected may be a “sectional” or, a “drum” machine. Rental equipment selection may be very limited usually only provided with minimum sized blades and in questionable condition due to abuse by inexperienced users.

A Sectional Machine has a power-head which is set up near the cleanout and the sections of cable are fed through the machine and added on as needed then after the drain is cleared the cable is backed out and sections are removed as they come out. This would be the top choice if you are going up on a roof to snake through a vent.

Drum Machines have a drum mounted on a hand truck which usually contain between 75 – 150′ of cable coiled inside the drum. The drum spins and the turning cable is fed out of the machine into the line. This would be my choice for almost everywhere except taking on the roof.

Either machine would have a cutter blade fastened on to the end of the cable. This cutter should be large enough to scrape the outside walls of the drain pipe to scrape all deposits from the inside wall of the pipe and cut roots that are coming into the pipe. Special gloves called “ugly gloves” are often used, to hold the cable while feeding it in and out of the pipe. These ugly gloves are rubber gloves coated with hard plastic grit that allows the cable to turn in the gloved hands without sticking to the rubber yet allow you to grip the turning cable to push and pull it in the line.

The turning cable is like a giant spring that has a tremendous amount of torque applied to it by the machine and you must hold it in your hands to guide it into the line. If you fail to control the torque of the spring it can turn into a pretzel instantly, and yes it may severely injure you. This is very likely to occur when you hit a strong root and the cable stops turning. You need to know just how much to let it build and be ready to snap the cable back and free for just a moment to allow it to unwind and plunge it back into the root while it is spinning fast. If the rental machine cable is in bad shape where it has been kinked previously it will easily wind up into a pretzel once again when under pressure.

Okay, are you really getting what I’m saying here? Drain cleaning is serious business and it takes about a full year before a drain cleaner gets really good at what he does. The skills needed involve diagnosis to determine the best way to approach the clogged line, skills to safely and effectively operate the equipment, and the ability to detect problems with the line that require repair…

A DIYer seldom has the knowledge and skills required to do a good job and if they avoid the possibility of serious injury at best they may punch a small hole through a clog as rental equipment is seldom provided with maximum blade sizes. Most often the DIYer tries unsuccessfully for a day or two then gives up and takes the best option. Your best option is to first call in a drain cleaning pro. Call a plumber and your drain can be clear within a couple of hours from when the call is placed.

Posted in How To Plumbing Tips, Sewer & Drain Tagged with: , , , , , , , , , , , ,
48 comments on “How to Unclog a Main Sewer Line
  1. Ed says:

    We are on a septic system. We bought the house 4 years ago and always had slow drain in both bathtubs. The kitchen drain / washing machine / clean out (coming out of a brick wall under the kitchen sink) is on the West side of the house, while the baths are on the East side. About 2 months ago we noted that some water on the floor after flushing the guest bath toilet. I thought maybe it was a bad wax ring, so I bought one to replace. We stopped using that toilet, until I had time to do repairs. Friday night, the toilet in the master bath didn’t flush and nearly overflowed. (We do not put paper down the toilets, plus use Rid-X on a 4 to 6 weeks basis) After a container of some liquid setting for 8 hours in the guess tub, and then flushing with hot water – the toilet in the guest flushed great and the tub drain ran good. No so for the master bath – still clogged. It was backing up in the guess toilet which was removed. I took up the old toilet from the guest and going to install a new one. But I will call a plumber on Monday (which is another headache trying to figure out which company to trust) because I could spend many days and many $$s on trying to clear the main sewer line myself. This will be a great lesson for me to watch and hope to find out where the septic tank is (different people say different spots!) Am I correct in thinking if they snake the cleanout by the kitchen through the house to the bath that – that is the way? I have never had problems like this – the house is brick with cement floors, I am used to wood floors that the plumbing is against outside walls. I guess I am looking for different scenarios, because I don’t understand all the things that could be wrong. I am a very good handy man but pipes in cement have me concerned. I don’t want to feel like I know nothing (but maybe the truth) on the issue. Thoughts please, thank you.(Tyler, Texas area)

    • Redwood says:

      Hi Ed,
      When was your septic tank last serviced? Is your home a 1 story home? If not are all the problems on the lowest floor?
      Hard to say what’s going on without being there or, more information. 4 years is within the time when a septic tank should be serviced but that depends on the system size and the number of people using it. If there is any possibility that the problem is a septic tank requiring servicing I’d have that done, many septic service companies will also take care of line problems to the tank.

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