After doing the "sniff test" we determined the smell was definitely coming from the main floor bathtub drain. My husband took out the plug and cleaned a lot of guck out of the drain and I attempted to remove any residual odour by using a "green" vinegar-baking soda-hot water solution. The smell stopped for about one day and now it is back. The lower level bathroom, with a bathtub, and master en-suite in the cab-over, with a shower, are not affected.
What could be causing this odour and what suggestions can you give us to eradicate the stench?
-- Harv & Pat Rosenbaum, e-mail
A. In many cases, the origin of seemingly mysterious odours in homes can be very difficult to pinpoint. Fortunately, plumbing odours are usually much easier to diagnose, as there are a limited number of possibilities. I will discuss these and try to help you identify the source of the problem.
The first possibility for the drain odour, and easiest to remedy, is debris in the drain, itself. This could be a combination of hair, soap, and various hair products that get stuck to the sides of the plastic drain pipes or in the trap underneath the tub. Correctly, you have taken the first step to address this problem with your environmentally friendly drain cleaning method. Unfortunately, while your solution may have temporarily eliminated some of the debris, it may not have cleared the drain of excess hair, which can still allow build-up of new soap and continued odours. While not as green as the vinegar and baking soda mixture, use of commercial drain cleaners may be more effective in removal of excess hair in the drains, allowing proper drainage of soapy water from the tub.
The second location of possible build-up of similar materials may be more insidious. All bathtubs have an overflow drain near the top of the tub that is rarely needed, unless the tub is overfilled. It is common for some people to fill the tub with too much water, so that a significant amount is drained through the overflow, once they enter the tub and displace some water. If this water is full of soap, bath oil, or bubble bath, it may also be causing a build-up within the overflow waste piping. This piping is connected to the drain piping below the tub, so an odour could easily be detected through the drain at the bottom of the tub, if this were the situation. The same "sniff test" you did on the tub drain should be done at the opening in the cover to the overflow, which is located below the tub spout. If the smell is stronger in this area than at the drain, the cover should be carefully removed and drain cleaner or a pipe cleaner used to clear this area, as well.
If the first two checks do not yield the results you seek. In that case, there is likely only one other possibility for the source of the odours. The problem, which I suspect is the true culprit, is improper venting for the tub drain. This may be much more difficult to determine, but proper repairs will yield a permanent solution.
To explain the problem of improper venting, without getting too technical, we must understand one basic principal of modern plumbing drains. Sufficient quantity of air must enter the top of the plumbing drain system, through the vents, to allow for proper drainage. Also, the drains must be configured according to specific guidelines, addressed in the plumbing codes, to allow for proper venting. If the venting is missing or the pipes improperly designed or installed, the drains many not function properly.
Sometimes, lack of proper venting can cause drains to run too slowly, which may lead to easy blockages or slow draining. In other cases, improper venting may cause drainage to be too fast, which can allow the water in the P-traps under bathroom fixtures to be siphoned out. In that situation, the traps may not be effective in achieving their primary function, to prevent sewer gas intrusion into the home from the drain system. The water in the bottom of the trap, which is located directly below the drain in your bathtub, must remain in place to prevent gasses from escaping from the larger drains, below. This gas can be quite strong smelling and noxious to occupants. I would suspect that this is the true cause of your problem and figuring out where the mistake has been made is the next step to eliminating the smell.
Improper venting issues can be due to either blockage of the vent pipes as they exit the home through the roof or improper pipe design or installation. Determination of either of these defects may be well beyond the capabilities of the average homeowner. Evaluation by a licensed plumber, which may involve walking on the roof or entering the attic and basement, may be the only way to see where the source of the venting defect is. If simple cleaning of the bathtub drains and overflow doesn't help, listen for gurgling noises after the water is fully drained, following a bath, which will be a sure sign to call the plumber.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the president of the Canadian Association of Home & Property Inspectors - Manitoba (www.cahpi.mb.ca). Questions can be e-mailed or sent to: Ask The Inspector, P.O. Box 69021, #110-2025 Corydon Ave., Winnipeg, MB. R3P 2G9. Ari can be reached at (204) 291-5358 or check out his website at www.trainedeye.ca.
