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bad oder from drain pipe

Long story short. There is a drain in the basement mostly for the ac and the hot water heater. I assume the kitchen sink connects up to this drain as well. Once time when the garbage disposal was over worked during canning season, the drain backed up into the basement and we had a mess.

Anyway, Last year we called out a plumber to fix the drain it was very slow. He cleared it up and we haven't had any problems until the city came by and "cleaned" out their pipes. Now we have a bad sewer gas smell coming back into the basement. It's not bad most of the time, but the past couple of days we've had to keep the door closed and won't go down there for very long. I do pour water down the drain thinking the trap went dry. I called the city and told them this problem started after their cleaning. They came to check it out but claim it's not their fault. The floor is dry meaning the water we use isn't backing up into the basement.

So do I need to call a plumber, or do is there something I can do myself to stop this foul smell?

A. Spruce
Re: bad oder from drain pipe

The AC and water heater should NOT be connected into the sewer system. The lines I believe you're talking about are condensate line for the ac and blow off line for the TP valve on the water heater. It is not uncommon for the ac line to have a small trap plumbed into it, but these should be terminating at a visible location so that if there's a problem it will be brought to your attention.

As for the floor drain, it should have a water trap in it to stop the odors. I would also assume that it should have a vent stack on it which could be plugged, causing the sewer odors to back up and burp past the water trap in the drain. I would start with checking the vent stacks from the roof.

Re: bad oder from drain pipe

Floor drains should be equipped with a special device that slowly dribbles water into them so the trap doesn't dry out. If your drain doesn't have this, the trap has probably dried out, and that could be the source of your bad odor. Before cleaning, the drain may have been so nearly plugged that the odor was minimal.

I'm assuming that the A/C condensate line and water heater T/P valve drain into this floor drain (above the grating).

Normally, I'd expect the condensate line to keep the trap full, but in the wintertime the A/C doesn't run, so there's no condensate to refill the trap. If you live in a climate that is very dry in the winter, the trap can dry out enough in just a couple of days to let gases past.

Try pouring a quart of water down the drain every day, and see if that helps. That will keep the trap full and the sewer gases at bay.

Re: bad oder from drain pipe

The drain is just a hole in the floor with a grate over it to keep large things from falling in. The AC has a PCP pipe that runs down and dumps out above the grate. The water heater needs a short hose in order to run out into the drain and not get on the floor. I pour a bucket of water down the drain on a daily basis. It does not seem to back up into the room as before, but yet the oder remains. I'll have to check the vents to see i f any of them may be a problem. I know there are problems with 1 vent with the range hood in the kitchen, but that's a different thread.

Once the drain was cleared out I made sure it wouldn't dry out. The A/C does help some during the summer, but but we didn't use it enough last year to make a difference. So once a month I would pour a bucket down the drain. Never had a problem until about a month or two ago.

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