How to unclog a main drain line

You can sometimes clear a main sewer line clog yourself, but only if the line has a working cleanout and the blockage is soft and close. The attempt is a hand auger at the cleanout, with a bucket, gloves and eye protection. If water rises as you open the cap, or the cable stops against something hard, stop. Our guide to main line drain cleaning shows what the professional version involves.

How do you know it is the main sewer line and not a single drain?

It is the main sewer line when more than one fixture is affected, and the lowest drain in the house backs up first. A toilet that gurgles when the washing machine drains, a shower that fills while you flush, or sewage in a floor drain all point to the main. A single slow sink does not.

Run a quick test. Flush the toilet farthest from the main line, then watch the lowest drain in the house, often a shower or a floor drain. If water rises there, the main sewer line is partly or fully blocked. Other signs of a main line clog:

• Several drains slow at once
• Gurgling from toilets and tubs
• A sewer smell that returns after you run water
• Wastewater pooling around a cleanout or a yard drain
• A sewer backup that returns after you clear it

Tampons, wipes sold as flushable, grease, and paper towels all create blockages, but a common cause in older homes is a pipe problem: roots in a joint, a belly in the line, or a cracked clay or cast iron section. A bigger plunger will not fix those.

Can you unclog a main sewer line yourself?

Yes, in simple cases. If you have a cleanout, a 50-foot hand-crank or power auger can clear a soft clog such as paper or grease. You cannot reliably clear roots, a collapsed pipe or a long blockage with a hand tool. Know the limits before you start, because a failed attempt can push the clog further in.

What suits a homeowner:

• A cleanout you can reach and open
• A soft, close blockage
• No sewage coming up as you work
• A willingness to stop at the first hard stop

What does not:

• Roots. Rotating cutters made for roots are heavy equipment. A hand snake will just poke a hole through.
• Long blockages beyond about 50 feet. Many home augers stop around there, and a long lateral can run farther.
• Broken or collapsed pipe. The cable will not pass, or it will snag and tear.
• Anything that happens more than once in a few months. That is a reason for a camera, not another round of cable.

If you are curious about rented machines, hydro jetting with a rented high-pressure unit can do damage in a weak pipe and injure the person using it. It is work for a trained operator.

How do I unblock my main sewer line at the cleanout?

Find the cleanout, a capped pipe, usually about 4 inches wide, at ground level near the house. Put on gloves and eye protection, place a bucket and towels, and loosen the cap slowly. If water rises, stop and retighten. If not, feed a hand auger in and turn the handle until it releases.

Steps:

1. Locate it. Check the front or side of the house, near a wall, and by the garage or a bathroom wall. Some are in a flower bed or under a cover.
2. Open slowly. The line can be full. Loosen the cap a quarter turn and let pressure out. If sewage pushes up past the thread, tighten it again and call for help.
3. Feed the cable. Push it in until it meets resistance, then crank clockwise. Pull it back slowly to bring up what it caught.
4. Flush with water. Run a hose into the cleanout, never a pressure washer, and watch whether it clears.
5. Clean up. Disinfect tools and the area. Wastewater carries bacteria, so wash your hands thoroughly.

Before any digging to reach a line you cannot find, call 811 or DigAlert. California requires notice at least two working days before excavating, and the call is free. Do not dig near the lateral until utilities are marked.

How do you use Instant Power main line cleaner?

Read the label on the bottle, since products differ. Products sold for main lines are usually poured into the cleanout or the toilet nearest the line and left for a set time. Treat them as maintenance for soft buildup. They will not remove roots, break a hard blockage or repair a damaged pipe.

Three cautions apply to any bottled main line product. Do not combine one with another drain product, with bleach or with acid. Do not use a chemical if sewage is already backing up, because it ends up sitting in the pipe and the standing water. Tell any plumber what you poured. Fumes that leave you coughing mean fresh air first, then a call to Poison Help at 1-800-222-1222.

The same applies to home remedies. See the best chemical to unclog a sewer line for what chemicals can and cannot do in a long line.

How to unclog a main sewer line without a cleanout?

Without a cleanout, the usual access points are the toilet, a tub or a roof vent, and each is harder and riskier than a cleanout. A toilet auger is not made for a main line. Some older Los Angeles homes have no cleanout, which is a good reason to have one installed.

What people try, and the trade-offs:

• Through the toilet. The toilet has to come off the floor to run a cable, and it must be reset with a new wax ring. It is a plumber's job to avoid cracked porcelain and leaks.
• Through a roof vent. It reaches the line but means working on a roof, which is a fall risk.
• From the street side. The lateral is yours to the public sewer, but the street connection is not a place to work.

If you have no cleanout, installing one is usually a good conclusion to a main line job. A cleanout allows a cable or camera in without pulling a toilet, and it can create a clean point of entry for every future visit. A local drain cleaner can quote it. See cleaning out a sewer cleanout for how they work.

When should you call for help with a sewer backup?

Call right away if sewage is coming into the house, if the water level rises at a fixture while you work, or if the cable meets a hard stop. A sewer backup is a health matter as well as a plumbing one. Keep people and pets away from the affected area and do not run more water.

In the City of Los Angeles, a blockage in the public main under the street is for LA Sanitation, and the number for the 24-hour Customer Care Center is 1-800-773-2489. A blocked private lateral is the property owner's responsibility, all the way to the connection under the street. If neighbors also have backups, mention that when you call.

For a backup in progress, see emergency sewer backup. You can schedule service online through the quote form, and a local drain cleaner will be lined up to look at the main line. The home page explains the wider process.

Questions people ask

How much does a plumber cost to unclog a main line?

Published Southern California prices for cabling a main line are often around $200 to $500, and hydro jetting is more, often $350 to $900. Emergency calls, no cleanout, roots and long runs raise the price. These are guides, so get a written quote. See main sewer line clog cost for more.

Can I do hydro jetting myself?

You can rent a small pressure jetter, but it is not a good idea for a main line. Misused, high-pressure water can damage old clay, cast iron and Orangeburg pipe, and the hose can whip. The nozzle also has to be matched to the pipe. Hire an operator who does this routinely.

What can I pour down my sewer line to unclog it?

Nothing you can buy reliably unclogs a main line. Hot water can soften grease, and enzyme products may help with soft buildup over time. Neither removes roots or a collapsed pipe, and strong chemicals add risk without a better result. Mechanical clearing, then a camera look, is the reliable route.

Can tampons clog the main sewer line?

Yes. Tampons, applicators, wipes and paper towels do not break down quickly. They snag on rough pipe or roots and catch more paper behind them. Even wipes sold as flushable can build up. Put them in the trash, not the toilet.

How do you unclog a pool main drain?

A pool main drain is not part of the sewer, so none of this applies. It is the suction outlet at the bottom of a pool. Do not dive down to clear it, since the suction is strong. Call a pool service technician.