I had a washing machine engineer out today to look over my machine and help me understand why my clothes smell bad after every wash. He said it is caused by the plumbing under the sink

Can you help me understand if this is correct?

Here is a photo, the left goes to drain, middle is sink, and right is washing machine. undersink

  • What does the stinky clothing smell like? Is it more likely to be chemical, biological, environmental, burning, etc.? Does the washing machine smell when it is empty? What does the detergent smell like? Is the water in use suitable for drinking? – wallyk Jun 26 '19 at 21:22
  • I see no photo. – DonBoitnott Jun 27 '19 at 13:33

I've never seen something like that before.

The most accepted form of plumbing requires a P-trap to prevent sewer gases from coming back into the house. In your case they might be flowing into your washing machine.

I haven't seen many washing machine to under sink connections before and the more typical thing is a long standpipe for a washing machine to pump the water into. I'd be fearful that the volume coming out of the washing machine would be too much for the sink assembly to handle in a short period of time possibly resulting in the water backing up into the sink until the volume had decreased.

  • The sink's trap should prevent sewer gases getting into the space. I don't think the problem is from that. While a top-loading clothes washer can inundate the plumbing and flush out the trap, in practice it is rarely a problem. When the tub is near empty, the flow greatly decreases and refills the trap. – wallyk Jun 26 '19 at 21:19
  • What is the name for the trap shown? I did a google image search for sink traps and don't see anything like it which leads me to believe it won't work very well. Possibly it is equivalent to a P-trap. Ignoring the high flow of the washer, the critical trap arm length could also be wrong causing a siphoning effect of the trap. Hard to determine without seeing how the trap hooks up to the next vertical section of pipe. – Fresh Codemonger Jun 26 '19 at 21:37
  • There is a lot that is looks very dodgy about that link from @wallyk. There is no contact, and no (visible) products, and in particular, no trap shown. – Martin Bonner supports Monica Jun 28 '19 at 10:36
  • With no air break in the line from the clothes washer, what's to prevent it from siphoning the trap water back into the washer after a cycle, thus letting sewer gasses in? – dwizum Jun 28 '19 at 19:46
  • 1
    I would assume that would be typical, if the washer was sitting on the floor that this cabinet was also sitting on - the "opening" into the washer is usually via the pump which is the lowest point and at the bottom of the washer. I mentioned it here because I bought a home many years ago where this was the case, the washer was hard-plumbed into a drain line that tee'd into a sink trap (vs the typical rubber hose into an open standpipe) and would routinely siphon the trap dry. – dwizum Jul 3 '19 at 12:16

I don't like the trap and would never install anything like this. Not because of the traps bad design though. I could live with using that trap. However I don't like that the exit is about an inch lower than the wash machine discharge. This seems an easy way for a small clog to create backup in the line. But I don't think this is an issue unless this is clogged up.

I also highly doubt it is your water. The easiest way to test this is to get a pail of water and soak clothes that smell as close to "nothing" as possible - so not your damp smell and not the fresh just washed smell. Let the clothes sit for a couple hours in the bucket and see if they smell after they dry. If this is your issue you are going to have to buy some sort of filtration system. But really this would need to be installed close to your tap as you might be stinky from showering due to this (hence the reason I don't think this is your issue - I have showered in well water houses... and you know).

The most logical reason is due to some mold or bacteria buildup in the wash machine. Take out all of the filters and clean them (you may have to read your user guide! the horror). Then run straight bleach for a few cycles, and leave machine open to dry. You may have to do this over a couple days a few times. You may also have to wipe under the seals and open up the back to see if there is anything around the drum. This is not an easy thing to fix other than pouring bleach/chemicals and letting your washer dry out. The repair guy sounded like a flake and should have told you this. He probably didn't want to touch it because he could do a pretty decent job taking apart and cleaning but miss something and you are still mad about a smell.

Everyone that does a decent amount of laundry should always be leaving the wash machine door open to dry faster and also to run an empty load on full/very hot with straight bleach. Your clothes will smell better, your machine will last longer.


We once had bad-smelling clothes after washing, then discovered that it was caused by the washing machine filter, that wasn't flushing away dirt water properly, but running it back into the machine, causing the bad smell.

All we did was clean the wash machine filters, then washed clothes returned to smell properly as washed.

  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. – Daniel Griscom Oct 18 '19 at 12:14

It's wrong the plumping need to plump separate to have ventilation pipe two of them to one drain to a vent pipe and then usually just the washer to a drain to vent pipe not all together to to risky for 1 to back up to another

  • 1
    Hello, and welcome to Home Improvement. It's hard to understand what you mean; would you edit your answer to make it into sentences? And, you should probably take our tour so you'll know how best to contribute here. – Daniel Griscom Oct 25 '20 at 19:16

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