Stinky, odorous kitchen sink in a high rise?
Do you come home sometimes and smell stink coming from your kitchen sink? Is the odor worse after being away for a few days? This can be from a combination of waste outlet pipe (below your sink) being at a height 24 inches above the floor and a garbage disposal that doesn’t drain as a result. This can be the case in older buildings.
The photos below shows the situation.
The garbage disposal outlet is below the waste outlet for the sink resulting in a deep trap and lots of standing water.
In it, you can see the waste outlet is just below the level of the sink. The garbage disposal outlet is well below the waste outlet. There’s also an array of piping allowing a large amount of water to pool. This water, when filled with food particles from the garbage disposal, acts like a petri dish allowing bacteria to multiply while the food decays. This is the source of the odor.
While traps containing water are under every sink, they’re usually short, flushing clear after the sink is used. This results from a lower waste outlet. In modern buildings, the waste outlet is at 16 inches above the floor (8 inches lower than this situation) and waste water reaching the far side of the trap runs downhill and out the outlet. This permits a shorter trap as well.
Whether you’re considering a renovation or just want a solution to your stinky sink situation, here are some possible solutions for you.
Understanding that stagnant water with food matter is the problem, simply using your garbage disposal less and running water through it for a while after every use is the simplest solution. You want the disposal to grind anything inside of it and then you want the debris to wash through all the traps flush the retained water clean. The garbage disposal ejects water with force so keep it running as water fills it.
How long you should run the water depends on your particular circumstance. Try 15 seconds with your faucet running full-on and see if that does the trick. Extend the time if necessary. If it does do the trick, try cutting it down to 10 seconds and so on until you get a feel for how long it takes.
If it takes too long to clear the trap or this doesn’t work at all, when you finished the cleansing cycle described above, turn the garbage disposal and water off, squirt some dishwasher detergent down the garbage disposal and run about a 2 cup of water into. Flick the switch for as short a time as possible. This will inject the soap into the trap while keeping some soap in the garbage disposal.
The soap acts as an antibacterial agent suppressing bacterial growth. Stopping the bacterial growth will stop the stink. Try more dishwashing liquid if this doesn’t work at first.
If you’re going on a trip, run the water longer than usual. You really want all the solid waste removed, then add more than the usual amount of soap.
If you’re ready to call a plumber or renovate here are more options.
The most obvious is to remove your garbage disposal if you don’t need it. That will cost about 250 to 600 dollars if your brother-in-law can’t do it and you need a tradesman.
If you’re renovating and can’t move the waste outlet lower, stick to a sink with a total depth from the countertop top surface of 8.5 inches. This means if it’s undermounted, add the thickness of the countertop to the depth of the sink. If the countertop is 1.25 inches at the sink and the sink is 7 inches deep for instance, the total is 8.25 so the sink will be fine. Avoid a garbage disposal for the above reasons.
On the other hand, replumbing the waste may be possible. In a single family home, it’s usually not a big deal but in a multi-unit building it’s uncertain. It depends on the existing situation There has to be a hub into the stack at a lower level than 16 inches. This hub allows a plumber to create a waste outlet at 16 inches. It’s usually a simple matter and costs $1000 to $1500 for the extra plumbing work alone though it might be more — you know plumbers!
If there’s no lower entry and you’re in an old building with a fragile cast iron stack, cutting into it presents danger. Old stacks can crack above or below your unit behind the neighbor’s walls. If this happens, it’s catastrophic.
One method to crack a waste pipe creates torque. Other methods create vibration. Both can crack pipe above or below the desired location.
The entire stack can be shut down while arrangements are made to repair it on an emergency basis. The repair might requiring cutting into the kitchen walls above and below and doing kitchen renovation work to bring their kitchen’s back into shape. Price tag for this tragedy: 30K plus with a very big possible plus. Your plumber’s insurance should cover it but it’s insurance so good luck. Their first answer will be “not our fault”.
No matter what happens your neighbors will not forget it.
What this means is that sometimes you won’t know what is possible until the renovation begins and the plumber looks in the wall to assess the situation. If you go this way, simply don’t buy the sink and garbage disposal upfront and wait to find out. In larger buildings, a building engineer can be a good source of information. They often can clear up the issue up before renovation begins.
There are ejector pumps which will fit below your sink so water can drain from a garbage disposal and be pumped out the waste outlet. It solves the problem but these are not commonly used. I’m not sure why, but there may be no good other than a lack of marketing. I have heard the pumps have a long term maintenance issues but there is no evidence of this online.
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Mitchell Newman, M.D. is the principal of Habitar Design and Stratagem Construction. He’s written numerous articles on construction issues and has received numerous industry awards including the Fixr’s Top 200 Influencers in the Home Design Industry in 2019. He is also a contributor to Wikihow.