lingering odor from bathroom pipes

[supadart]

Hi all,

Recently had the septic tank in the yard cleaned due to an odor noticed in the bathroom. No probelms there...however, the odor is still present - although not as bad - in the bathroom. Have run plenty of water down drains of sink, toilet and tub in hopes that it may help. The pipes never did backup, but the wastewater level in the tank was just touching the wastepipe in the tank. Any thoughts?

[LazyPup]

Locating the source of an odor can be a very difficult task, however I will discuss some of the more common sources in hopes that it may help you narrow down the search.

Obiously the most common source of sewer gas smell is a leak in the DWV (Drain, Waste & Vent system.) If the bathroom is built over a crawlspace or on slab construction even a sizeable leak may go unnoticed for an extended period of time. If it is over a crawl space begin by looking in the crawl space for evidence of a leak. Usually if there is a leak in the crawlspace the odor will be very evident in there. Also examine the piping for evidence of water, or stains streaking down the pipes that would indicate there may be a minor leak. Examine the floor of the crawlspace for any signs of standing water or in a worst case, signs of wet toilet tissue clinging on pipes, structural materials or on the floor.

If the bathroom is constructed over a basement examine the entire floor area from underneath. Even minor evidence of water may indicate a leak in the piping.

Is there possibly an unused drain in the room? A floor drain, seldom used shower stall or perhaps an unused laundry standpipe? If so, the water in that trap may have evaporated out. The solution is to pour about a quart of water into that drain to refill the trap, then add about a 1/4 cup of liquid cooking oil, which will float on top of the water and retard the rate of evaporation, while still leaving the drain fully operational.

Check in the cabinet under the lavatory bowl. Is there perhaps an air inlet valve (studor vent, or cheater vent) that is not functioning correctly? It will look like a vertical stub of 1.5in diameter pipe with a black plastic cap on the top with slots on the sides of the cap.

If you have a service access panel for the bathtub, open the panel and examine the subfloor area under the tub for signs of a leak. (You may need to use a flashlight and mirror to examine that area.)

Depending upon which plumbing code is in effect in your area, there are some other areas to check. The Uniform Plumbing Code (UPC) requires all vents to terminate through the roof to open air, However, the International Residential Code(IRC) only requires the main vent to terminate through the roof. Although never a good practice, the IRC permits auxillary vents to terminate in the attic space. If you have a vent terminated in the attic space you potentially will have two problems. The sewer gases will collect in the attic space, and given tht sewer gases are heavier than air, they will then permeat down through ceiling and structural materials into the house. The second problem is that excess moisture in the form of steam from how water discharge will condensate into the insulation, which will not only cause odor problems but can render the insulation useless.

The IRC also permits horizontal vents which terminate through the wall in the same manner as a laundry drier vent, subject to some restrictions about the proximity of windows, doors or other openings into the structure.

Sidewall vents are required to have screens to prevent birds or rodents from entering the vents, but screens will corode away rather quickly and require periodic inspection to insure the screens are in good repair and the vents are not obstructed by bird or insect nests.

You stated that the water level in your septic tank was up to the level of the drain input line. That is typical and is a sign that the tank is working correctly. Basically a septic tank is a large square concrete box that has an internal baffel. The waste enters the tank from one end and is contained by the baffle while bacteria break down the solids. Water then discharges from the opposite end of the tank and goes into the perforated leach field pipe where it is absorbed into the soil. Since water seeks its own level, it can pass through the baffle while maintaining the same level in both compartments.

[supadart]

Thanks for the info.

The house is on a slab. We only moved in about 2 months ago, so I'll start by checking around for access panels, leaky pipes and dry traps - although I did run water down each drain pipe (sink, tub and toilet). I'll also check for a vent as mentioned.

Is it possible that the wax ring under the toilet may be a culprit? The odor is not present in the other bathroom, laundry or kitchen area, and seems to be worst around the guest bath toilet - which is also the closest area to the septic tank.

Thanks for the tank drawing too. Never knew much about those things.

-Gary

[LazyPup]

I would start by replacing the wax ring. A new wax ring will only cost about $1.50 and is rather simple to change out.

To change a wax ring, begin by turning the toilet tank water supply off.

Flush the toilet to discharge as much water as possible out of the tank.

Use a plunger to force as much water out of the bowl trap as you can.

Disconnect the water supply line at the tank.

Remove the toilet mount bolts on the base of the bowl.

I like to lay a large trash bag on the floor so you can lift the toilet and set it down in the trash bag, then slip the bag up around the bowl before you try moving the toilet. That will prevent the excess water in the trap from leaking out on the floor, and will prevent getting wax from the old wax ring on the floor. I then set the toilet in the bathtub where i can carefully tip it over to dump the excess water out and reach the base of the bowl to remove any old wax still clinging to the base of the bowl.

Next, use a putty knife to remove as much of the old wax as you can from the closet flange. Be especially careful to check the inside diameter of the closet flange to insure there is not an old wax ring plastic guide flange still lodged in the closet flange.

Now carefully examine the closet flange. Make sure the flange is not cracked or broken in the area where the closet mount bolts attach to the flange. Check the vertical height of the flange. Properly the underside of the flange should be flush with the finish floor and the top of the flange is now about 1/4 to 3/8 of an inch above the floor. The code prohibits a closet flange being flush with or recessed into the finished floor.