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The Old Method of Trapping Sewer Gas.

In areas of Massachusetts and Rhode Island, sewer blockages and clogged drains are often the result of having a main line trap. Main line sewer traps were originally installed with a few purposes in mind. One reason to install a trap on the sewer line was to literally trap debris or objects accidentally finding their way into the sewer line. Intended to be easy, trap cleanouts were installed with the idea of a home owner being able to remove the obstruction by removing clean out plugs and physically removing the items in the trap. The vision was lost somewhere in history and main line sewer traps have shown up in places where they are difficult to service from day one of their installation.

Throughout Rhode Island, a drain cleaning technician will encounter difficulty with main line traps being buried in such cities as Pawtucket, Cranston, Providence and Woonsocket. The locations around South Eastern Massachusetts where a sewer trap may or may not be installed are not consistent. For Example, throughout New Bedford, the drain cleaning technician may find a street where a few houses have traps and others do not have main line sewer traps.

In the drawing above, you can see the trap as a ‘u’ shape in the sewer line. It has two caps pointing to the sky. Here in the drawing, the capped ends are labeled as “clean outs”. This is where the Sewer Cleaning Technician will first attempt to clear a blockage from since sewer backups often occur here at the trap or “house trap”. However, if the trap cleanouts are not accessible, then removing the cleanout plug from the downstream side is not an option. In some cases, the trap is unearthed by excavation and clearing the line of a blockage is much more expensive than if the trap were accessible to the technician. The trap is no longer necessary. If the trap has to be excavated to service it, do not allow it to remain in the line. Replace it with a strait piece of pipe. Or, if your home or place of business is in Rhode Island, the plumbing code in Rhode Island requires the trap be replaced with a back water valve. Back water valves are a great idea, anyway. Ask anyone who has had sewage from the main city sewer, back into their home. Not just sewer water from your house. So, you can’t control it. You will get sewage from upstream of your house with out a back water valve if the city main backs up!

Reasons for drain cleaning difficulty

  • the trap itself inhibits the ability of the sewer and drain cleaning technician from getting the sewer cleaning cable across the trap. So, the outlet side of the trap must be opened.
  • the trap may not have been opened in decades. For the sewer and drain cleaning tech., this often means cutting the cap out or using a chisel to pry it out.
  • the trap is often buried in the ground, making the task of opening the trap impossible for sewer and drain cleaning technicians. This would then mean the technician will have to play a game of skill against the trap to manipulate a cable or a jet hose through the trap to clear the clogged sewer line.

More purpose was given to main line sewer traps. Traps were installed in mainline residential sewers to prevent sewer gas and rodents from entering the house and allow the home owner an opportunity to prevent sewer blockage by trapping foreign objects that are not flushable. However, if the trap is not serviceable, and buried in the earth, one of the advantages to having a trap is gone.

House traps are also irrelevant due to the fact once the piping on the house side of the trap becomes soiled, noxious and dangerous gases still infiltrate the home. So, the practice of installing a trap at every fixture in the house was implemented.

Having a house trap in the mainline and a trap at a fixture is what is known by plumbers and drain cleaners as double trapping. The international plumbing code forbids double trapping. Double trapping in itself can inhibit the flow of sewage and promote sewer and drain back-ups. So, it is worth having the main line trap removed in order to avoid inconvenience and costly sewer clogs.

House traps are very common in Pawtucket, Rhode Island; Cranston, Rhode Island; Providence and Woonsocket. However, they are spotty and often unpredictable as to where the sewer and drain cleaning professionals will find them with in the cities of Massachusetts.


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