Sewer odor has experts stumped

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    • #278684
      Avatar photoAnonymous

        Our home is 16 years old. The leech field failed & last Sept. we had a new septic system and field put in. Last winter when it was real cold we smelled sewer odors – just on the north side of the house, and the sewer is on the south side.

        This summer we smell it strong in the mornings after we all take showers. Once in a while when doing lots of laundry we have a small amount of gray water back up into the garage from the drain hole.

        Fearing our new system had failed, the engineer inspected it, and said it was working properly. He said to call a plumber who was a drain expert and have him snake the lines from the house. When the guy came out yesterday he inspected the sewer and said it is working great. We ran over 100 gallons of water, and no back up in the garage. The leech field is dry and the water is pouring into the spetic tank very quickly. He said snaking it would not solve anything and only cost more money.

        Curiously, he said there were two vents on the roof above where the toilets are, and since the toilets are on the same wall, he said it was odd to have two. There is also another vent on the garage, (on the north side where the smell is) and it is lower than the other two, and he said it is larger in diameter than normal.

        He feels the odor is coming from the vent and suggested we duct tape it shut as long as the indoor plumbing still works fine.

        We never had any problems in 16 years, not until the new system was out in, which everyone says is working wonderfully. Why all of a sudden are we getting this smell? One night after two of us took baths I went outside to see if there was an odor, and there was not ANY sewer smell. Yesterday when we ran 100 gallons of water through there was only a slight odor, and again on the north side.

        ANY suggestions are appreciated!

      • #299061
        Avatar photoRichard

          I am not a plumber, but a chemist that does water testing. Does this gas smell like sulfur? If so, your problem is probably bacterial. I would (if its possible, again, I’m not a plumber) take a sample from your tank and check for bacterial contamination.

        • #299062
          Avatar photoJohn Aldrich1

            Sue44, over the course of my career, I have replaced many septic systems, and have had the opportunity to peer into many other septic tanks. The inlet structures of some of these older tanks consisted of 90 degree elbows turned down into the water. In conversations with some of the ‘old timers’ who installed these systems, it was revealed that this practice was performed to minimized the populations of small flying insects, who made their homes on the scum layer in the tank. The insects would be flushed with the sewage into the tank, and then have no means of escape. This practice also prevents the odorous gasses, created by microbial digestion, from being vented up through the vent system to the roof. Occasionally, on some systems, the odorous gasses are carried down into the yard by downdraft air currents.

            The inlet structures of the newer systems consist of sanitary tees with the top of the tee above the water, and scum layer. This allows the digestion gasses to be vented through the house vent system to the roof. I have found that on those few systems that have the downdraft problem, the tops of the tees were capped to exclude the gasses.

            The septic system contractor that installed your new system, no doubt, followed the requirements of the regulations, and installed an uncapped sanitary tee in your new septic tank to allow the gasses to be vented.

            The solution to the downdraft problem is to install “Sweet Air” activated carbon roof vent filters on all of the vents on the roof. Do not block the vents with duct tape. The vent filters can be viewed, and obtained on the web page of Richard Septic Systems, of Torrington, Connecticut. The web page address is:

            Good luck, and I hope this solves your problem. JWA

          • #299063
            Avatar photoSue44

              Thanks John! We extended the pipe on the north side of the house about 2 feet and it has helped immensely, but there is still a slight odor. I am checking out the sweet air filters, but these only last 3 months. I live in Alaska and don’t relish the idea of climbing up there every 90 days to change them. There is another brand that sound like they do the same thing, but they are around $50 and last 5 years. Then they can be recharged for $10. What is the difference between these two products?

            • #299064
              Avatar photoJohn Aldrich1

                Sue44, I think the Sweet Air Filter is “GUARANTEED” for 3 months, but actually function for a much longer period of time. The first filters that I installed have been functioning for 6 years now on the original activated carbon load. The carbon can be replaced when all of the sorption sites are taken, and the odor removal effect is diminished. The activated carbon odor removal effect is a diminishing effect, and is determined by the volume of odorous gasses that pass through it, and the volume of activated carbon that is contained in the filter. As the volume, and concentration of the gasses passing through the carbon increases, the service life of the activated carbon decreases.

                I have no financial interest in the Sweet Air Filter Company, nor in their distributor that I recommended, Richard Septic Systems, Inc., so it matters not to me which brand of filter you purchase, nor from whom the purchase is made. Make your buying decision on the basis of a comparative analysis of the value received from the 2 products.

                My recommendation is based on the experience that I have had with these filters. Good Luck. JWA

              • #299065
                Avatar photoGuest

                  put a mech vent on stack or some people call it a oneway vent lets air in but not out

                • #299066
                  Avatar photorbspry

                    John–I have a question regarding the sweet-air vents. We had/have a strong sewer smell coming from our roof vents after we added on an addition to our home. We put the sweet-air vents on and HORRAY!! the smell dissapaited and life was wonderful again. Ok, the next day a strong sewer gas smell is seeping from our toilet in the basement. We replaced the wax ring and the smell remained. So, we took the sweet-air vents back off and now the basement bathroom smells great. Back to square one. Please help!! I have been trying to figure this out for seven months. The sweet-air vents shouldn’t be blocking THAT much air–why do you think this is happening?? I am so disheartened. Any replies would be appreciated.

                  • #299067
                    Avatar photoJohn Aldrich1

                      vitos plumbing, I am unfamiliar with the device that you refer to as a “mech vent”, or “oneway vent” for use on a roof vent stack. I do know that these devices (ProVents) are sometimes used on drains on kitchen islands in leiu of conventional vent systems, but they are generally not recommended.

                      Where will the septic tank gasses be vented when a oneway vent is installed on a roof vent pipe in a system that relies on a septic tank effluent pump? The gasses will be vented through the soil above the leach field on a gravity flow system if the leach field is not completely saturated. However, if there is no pathway for gas venting because of the trap provided by the pump, or because the septic tank effluent pipe is full of water, the sewer gasses will accumulate in the air space above the scum layer in the septic tank, and will become pressurized. This pressurized gas would then force its way through the traps in the drains in the house.

                      If the device to which you refer overcomes this potential problem, please explain the mechanism to me, and send information as to where I can see such a vent. My e-mail address is [email protected] JWA

                    • #299068
                      Avatar photofourth year

                        The tees in the inlet and outlet are not to vent gases. They are to allow the baffle pipes to be unplugged if grease or other materials plug the risers. A septic system is basically a closed system and if Studor type vent mechanisms are put on all the vents,(or the vents duct taped closed), the system will be air bound and nothing may work properly.

                      • #299069
                        Avatar photoJohn Aldrich1

                          Sue44 and fourth year, the sanitary tees on the inlet and outlet of a septic tank serve dual purposes. The inlet tee allows for access for cleaning purposes as fourth year has stated, and it allows for gasses to be vented back through the house venting system to the roof.

                          The purpose of the outlet tee, or baffle, is to prevent the scum layer from flowing into the leach field piping, and also allows for some gas venting. The sewage effluent is drawn from the sludge-free zone below the scum layer, and then applied to the leach field. A sanitary tee on the outlet pipe also allows for the installation of a recent innovation in septic system technology, the septic tank effluent filter.

                          A septic tank is not a closed system in that the digestion gasses created in the tank must be vented in some manner, and of course the sewage effluent flows into the leach field. Most of the gasses produced by microbial digestion are vented back through the plumbing system in the house.

                          Main sewer line traps have been specified in the past to exclude septic tank gasses from the house venting system. The digestion gasses in the tank would then be vented through the leach field piping and then through the soil above the leach field. The soil would then “scrub” the odorous gasses that are lighter than air before rising to the atmosphere. These main sewer traps proved to be a major maintenance problem, were subject to clogging, and were difficult to clean. They are specifically disallowed in most ISDS Regulations.

                          Plumbing technology is constantly evolving, so if vitos plumbing knows of a vent system that will overcome the apparent problems that fourth year, and I have with that recommendation, I am interested in learning of this technology. JWA

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