Can't fix fishy odor.

[Jack.Straw]

Hi guys. We have a double sink in the kitchen that is omitting a seriously bad smell. It doesn't smell of sulfur or sewer gasses. It's more of a fishy smell. I recently removed all the pipes shown in the pictures below. I washed them with a big bottle brush in a mixture of bleach and water. There was no build up in any of the pipes, but i scrubbed them all regardless. I also went ahead and replaced the P trap. The pipes themselves didn't have much of a smell after cleaning. When i reinstalled everything, the odor came right back.

My next theory was the dishwasher. The drain line for the dishwasher comes in past the trap, so I could imagine the smell originating from that. We have a self cleaning dishwasher, but I took apart the glass trap anyway and found nothing in there. There also is no foul smell coming from inside the dishwasher.

I'm at a complete loss as to next steps. My only theory is that somehow the P trap isn't retaining enough water to block sewer gasses. I think that theory is strengthened slightly by the fact that the sink doesn't seem to smell 100% of the time. That is, sometimes it's way worse than other times. If you have any thoughts i'd appreciate hearing them. Thanks!

 

[Reach4]

My only theory is that somehow the P trap isn't retaining enough water to block sewer gasses.

You could put in a transparent p-trap temporarily as a diagnostic aid.

If you backlight your current trap with a bright flashlight, you might be able to see the levels.

Do you get the smell inside of the sink cabinet?

 

[Sponsor]

 

[Jack.Straw]

You could put in a transparent p-trap temporarily as a diagnostic aid.

If you backlight your current trap with a bright flashlight, you might be able to see the levels.

Do you get the smell inside of the sink cabinet?

There's no smell in the cabinet. I just back-lit the P trap and it seems to be full of water, so there goes that theory.

 

[Reach4]

There's no smell in the cabinet. I just back-lit the P trap and it seems to be full of water, so there goes that theory.

Re-check when the smell comes back.

 

[WorthFlorida]

Do you sense the smell under the cabinet when you smell it in the room? When you smell it put a flashlight or drop light behind the trap to see if you can see the water level in the trap. The material is a bit translucent. Is the odor at any particular time such as another fixture being used, a washing machine or a shower in use? If your washing machine is nearby, check it for odors. Front load HE machines can get moldy behind the door seal.

Newer dishwashers have filters in them at the bottom near the spray arm. My Bosch machine did it once and it was filled with old food debris. It stunk like old garbage.

Try removing the trap arm to the wall drain pipe and cap it off with a wet rag and clear wrap to seal it off or plug up both drains in the sink. Then wait awhile to see if the odor returns. Do you have a hood over the range that exhausts outside? There might be a dead critter in it if you do. Maybe a dead mouse behind the kick plate of the cabinet.

I see what looks like an old water stain at the wall. Check further down the wall as there could be a small leak keeping things damp and moldy. I had a window leak once where it dripped behind drywall at the window sill and the entire wall behind the cabinet went green. Never saw the water until it started to stink.

 

[Bannerman]

Unless there is improper venting after the 'P' trap that is resulting in the water in the 'P' trap being siphoned out, the trap should contain an ample quantity to prevent sewer gas from the sewer system from being emitted from the drain.

The stain on the wall below where the drain pipe (trap arm) penetrates the wall indicates there was and maybe continues to be a leak in that pipe or at a pipe joint within the wall directly past the drywall.

For the cause of the odor, I would be suspicious of the dishwasher drain line both where it connects to the sink's drain and directly before. The flexible DW drain tube is sitting below the drain connection so debris may be remaining in the flexible tube or, some debris maybe flowing from the sink drain back into the flexible tube.

Suggest elevating the DW tube so that tube is placed as high as possible between the DW and the sink drain such as directly under the counter top. If the DW drain T is also rotated slightly so the connection is located at or near the top of the horizontal drain pipe, then the DW tube should drain into the sink drain pipe with less potential of the discharge from the sink backing up into the DW drain tube.

If the DW is located in the adjacent cabinet to the sink's cabinet, then drilling a hole directly below the counter top through the gable between the cabinets will provide an elevated path for the DW's flexible hose.

You may also want to place a small amount (1/2 - 1 oz) of liquid chlorine bleach into the DW at the start of the next few cycles. The bleach will assist to eliminate odour and mold within the DW's flexible drain tube.

 

[Jack.Straw]

I'm sorry it took so long for me to get back here. I want to thank everyone so much for taking the time to make suggestions. I'm fairly embarrassed to report that the smell was coming from a hidden food item rotting behind a basket that was sitting on the counter near the sink. I couldn't believe it. It seemed to be emanating from the drain, and the smell wasn't persistent. Lesson learned here! Thanks again