More Blog Posts on Similar Subjects:

  1. So the water heater is older...what’s the big deal?

  2. Why is my water heater making strange (rumbling, gurgling, knocking or banging) noises?

  3. What are the pipes on my roof?

  4. Do I have to get a larger septic tank when I build a home addition?

  5. Should I upgrade to a tankless water heater?

  6. How old is that water heater?

  7. Should I call a plumber or septic tank contractor when my septic tank backs up into the house?

  8. Should I call a plumber or septic tank contractor when my septic tank backs up into the house?

  9. What’s the powdery crust on the pipe connections at the water heater?

  10. Do you check the plumbing under the floor slab?

  11. What is a “cross connection” in a home’s plumbing system?

  12. How much does it cost to replace the plumbing pipe in a house?

  13. This home has galvanized water pipe. Is that a problem?

  14. What causes low water pressure in a house?

  15. What’s the flip-up handle on the water heater for?

  16. My well water test came back positive for bacteria. What should I do?

  17. Do you test the well water?

  18. What are the pipes on my roof?

  19. How can I tell what type of plumbing pipe I have?

  20. How does a home inspector evaluate wood rot?

  21. How can I determine the age of a water heater if the serial number is missing or decoding it is impossible?

  22. What is a saddle valve?

  23. How do you test a shower pan for leaks?

  24. What is a grinder pump?

  25. What can I do to make my water heater last longer?

  26. What is that little tank on top of the water heater for?

  27. What are the minimum clearances around a toilet?

  28. What is the average lifespan of a water heater?

  29. What is a dielectric union?

  30. What is a heat pump water heater?

  31. What are the common problems to look for when the plumbing has been replaced in a house?

  32. What is the average life expectancy of copper pipe?

  33. Why can’t PVC pipe be used for water pipe inside a house?

  34. What is the average life expectancy of PVC pipe?

  35. What is an auto vent, air admittance valve, or check vent?

  36. Why is a European-style bottle trap not approved by the plumbing codes in the U.S.?

  37. What is the average life expectancy of CPVC pipe?

  38. What is an FVIR water heater?

  39. What are the requirements for installing a gas appliance connector?

  40. What is an escutcheon plate?

  41. Why is sunlight exposure bad for PVC pipe?

  42. Is the hot water faucet handle required to be on the left?

  43. Why is a backflow preventer required on lawn sprinkler systems?

  44. How do you find a broken water pipe leak under the floor slab?

  45. What is a sediment trap or dirt leg?

  46. Is a hot water faucet required at a washing machine?

  47. What is the purpose of a thermostatic mixing valve above a water heater?

How to Look

at a House


A blog with answers
to your questions about
HOME INSPECTION
and HOME MAINTENANCE

Search This Blog

Welcome to our blog!
We want you to be an informed homebuyer, and each blog post is a question that we have answered for our friends and customers over the years. Hope they help you make a good choice for your next home.

  The second cause of a sewer gas leak is more difficult to track down. A crack, or any other damage that causes an opening in a vent pipe (the vertical pipe that extends through the roof), the trap arm (the pipe between the trap and the vent pipe, or the base of a toilet will also allow sewer gas to escape. Also, the failure of drain pipes in the crawl space or under the floor slab can allow gas to rise into the house. If you have filled all the traps around the home and still have a lingering odor, it’s time to call a plumber to locate the pipe damage.

   The third stinky-gas cause occurs outside the home where the pipes that exhaust the sewer gas into the atmosphere terminate. They are supposed to extend above the roof and away from any windows or other openings into the home. But if the top of a vent pipe is below the roof and near a window, a breeze blowing in the right direction will push the sewer gas back into the the house. Check outside any rooms with a sewer gas smell for vent pipes nearby. A plumber can usually fix a vent pipe termination problem easily.

    So, how dangerous is sewer gas? According to the International Association of Certified Home Inspectors (interNACHI), sewer gas accumulation in a home creates the following risks:

Hydrogen Sulfide Poisoning. Hydrogen sulfide is an explosive and extremely toxic gas that can impair several different systems in the body at once, most notably the nervous system. So potent that it can be smelled at 0.47 parts per billion by half of human adults, the gas will begin to cause eye irritation at 10 parts per million (ppm) and eye damage at 50 ppm. Other low-level symptoms include nervousness, dizziness, nausea, headache and drowsiness. Exposure to higher concentrations can lead to pulmonary edema, and still higher levels (800 to 1,000 ppm) will cause almost immediate loss of consciousness and death;  

  1. Asphyxiation. When sewer gases diffuse into household air, they gradually displace oxygen and suffocate occupants. The effects of oxygen deficiency include headache, nausea, dizziness and unconsciousness. At very low oxygen concentrations (less than 12%), unconsciousness and death will occur quickly and without warning. Oxygen will be at its lowest concentrations in the basement, which is where heavy sewer gases, principally methane, are likely to collect.

  2. Fire or Explosion. Methane and hydrogen sulfide are explosive components of sewer gas. Vapors from improperly disposed fuel can further increase the risk of fire or explosion.

  3. Odor. Hydrogen sulfide is responsible for sewer gas’s characteristic rotten-egg smell, which can be overbearing even at extremely low concentrations. The gas’s odor is a safeguard, however, because it alerts building occupants to the leak long before they’re in any serious danger. It is important to note that at roughly 100 ppm, the olfactory nerve becomes paralyzed, removing the victim’s sense of smell and, subsequently, their awareness of the danger. Another "warning smell" comes from ammonia, which will sear the nostrils and progressively irritate the mucous membranes and respiratory tract. This gas, unlike hydrogen sulfide, is sufficiently irritating that building occupants are likely to vacate before its concentration rises to toxic levels.

    If the smell is so intense that you think a high level of sewer gas has accumulated in the home you should evacuate and call the fire department for assistance. Because methane can be explosive, don’t create any spark from an electric appliance, matches or cigarette lighter.
    For a lower level of gas, just open the windows while you search for the source. Clearing the air will also help you pinpoint the location of the problem.


While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
©2015 - McGarry and Madsen Inspection.

Click Below to Link
to Collections of
Blog Posts by Subject

Search This Blog