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House Trap

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  • House Trap

    I do alot of work in neighborhoods, that have houses built in the 1940's & before. Alot of them have problems with the house traps, under basement floors, that is connected to the sanitary sewer, & serves the sanitary drains, inside,(not the storm). These traps are known to be problematic, as they age,cuz the cast iron gets rough on the inside, & toilet paper & other debris get stuck, causing frequent backups. I have had many of the traps rot out, & would cause nasty odors, sewer flies, and whatever else, in basement, from sewage leaking out underground. Also makes it harder to clean out sewer line, & impossible to camera.
    Well I take alot of these out, & just put in a straight piece of pipe, w/ wye & cleanout, thus eliminating house trap altogether. I am in the midst of starting one of these next week, & the customer asked me,: why did they install a house trap on the main sanitary drain in the 1st place? I didn't have a good explanation, cuz everything in the house is individually trapped anyway. So I'm asking the pros.
    Why did they put in house traps, on the sanitary sewer, (or main drain) in the first place?

  • #2
    Re: House Trap

    In Eastern Pennsylvania, house traps are extremely common but we have vents on them and they are located outside in the yard. Townships and Sewer Authorities require building traps here, and they are only legal here because the powers that be can supersede the Plumbing code. I personally like having a building trap because I can stick my cable down either way without going inside the house or to the roof to cable a drain. Yes building traps could be considered "double trapping" or a "running trap" but our Plumbing code clearly states an exception can be made.

    However in your situation, I wouldn't want a building trap because is not vented from what you described, and it's under the concrete floor.

    My best guess would be that your area required building traps back in the day as a secondary precaution against fixture trap evaporation or siphonage.
    Last edited by Flux; 10-20-2011, 06:26 PM.


    • #3
      Re: House Trap

      Never heard of such a thing but my guess? Would be to still pertect the hous from sewer gas back when houses werent vented and back siphonage of traps may have occured just a guess i cant see why or what other purpose they ould serve besides additional service work for plumbers ?