After the filter -- which you said you've already done -- next place I'd look at is the drain hose, especially at the point it connects to the drain under the sink. Easy to disconnect and examine. Look at the hose for kinks and look into the discharge outlet for obstructions. Leave the hose-end out and get a bucket big enough to allow fill/drain from the DW. Allow single fill/drain to empty into the bucket. Suspect you'll learn lots in just a few minutes.

I think you will have serious issues with suds lock in that long 3/4 inch PVC pipe. However, it will come down to you usage patterns and your specific application and equipment choice. Is it a top load? Top load has to pass about 10 to 14 gallons per fill out that little tube fairly quickly. A front load may have only 5 to 8 gallons to get out. Had the horizontal tube been 1.5 inch or 2 inch, you would have a higher success rate. If a top load, does it have neutral drain (pump all the way out before attempting spin)? Speed Queen does not have neutral drain and would have a tough time with this set up, it would burn out the belt quicker attempting to spin the load with water, might even eject water over the tub cover. An old whirlpool top load would likely pop the splutch from overload over time, a time consuming repair for the average Joe, but at least the part is cheap. You will definitely have more dry time as a result and more loads where the motor current detection software will keep it from going to top speed. If you have an electronic model with some flexibility you may be able to program a little more spin time. But be aware, spinning is generally what wears out the machine. If it had a default spin time of 5 min, changing to 6 min will take away about 20% of the expected machine life. Spinning wears the seal and bearing systems in particular as well as the pump, shocks if front loader, and pivot element if a top loader. High in rush currents are harsh on the motor if the load is high. Siphon risk? Hard to say. Most units have a duck bill back flow preventer just downstream of the pump so that after the water leaves the pump, it can't return to the machine. But generally you want the outlet at the drain pipe to be above the top water line on the machine. Your local inspector would likely not be very happy! Good luck. Laundryvet

Please allow me to post my opinion and experience on this stinky issue. I am the owner of a HE3T washer, and I am really unhappy with it, mainly because of the smelly and moldy issue, that crept up on us unexpectedly. My wife and I have 4 kids, so doing laundry is a daily affair, and not to be underestimated or procrastinated either... I am on the verge of throwing that ugly beast out of the laundry room for good. It is unbearably revolting to pick up an (alleged) clean towel to dry one's face just out of the shower, and "smear" moldy smell all over you. The vomit factor is very high on this one.... :-( However, I want to highlight a point, and that this issue is NOT an issue with ALL the FL (front loader) washing machines in general. Maybe just US made ones... Overseas, ( Italy ) where I grew up, FL are 99.999999% of laundry machines available on the market and this issue is completely unknown. To put it simply, I am now 45 years of age, I have lived in Italy 28 of those years, and I have never, ever, seen or heard of moldy smell on clean laundry out of the washer. Never. If you knew my mother (she redefines the word "neat freak") you would understand. Just the hint of a remote possibility of having mold in the washer and/or laundry, would bring that washer in the front yard in flames... Seriously, I believe US manufacturers have gone wrong somewhere in the making of this machines. They either cut one too may corners ( quality of rubber, maybe ?) or are attempting to reduce the amount of water in the cycle at the point where the quality of the rinse cycle is not an issue with them, and us as consumers are not part of the equation. I just came back from a one year of living in Italy with wife and kids, and the FIRST thing we notice, ever single time we go over there, is how much fresher and overall incredibly better smell of "clean laundry" they have from their washers. I know, we are weird... and on the contrary, as soon as we are back to the US, and to our $#@! HE3T, we pick up the moldy smell again. The customer/user/consumer SHOULD NOT have to do any gimmicks or use any "special" tablets, in order to operate these washers, or any washer, for that matter, NOT A SINGLE ONE. This washers are NOT cheap and they should just... well, work. Living in Italy for the last 12 months, we used two washers, one that came with the apartment we rented, and besides a slower spin cycle, it worked as expected (put dirty clothes in, put detergent, push the button, wait, get wet CLEAN laundry out, END OF THE story. Then the landlord needed his washer back, and for a "rent discount" he took that one back, and I got my old 12 years old Miele washer out of storage. This Miele has a somewhat smaller load capacity than most, and it worked for a family of 6 for a long time. Same for my mother's Candy ( Italian brand), and my sister's old Italian washer (San Giorgio). That one lasted 16 years of day in and day out operation for a family of six. It is just so frustrating, since I know that as a concept, FL do work very well, I have seen it work for decades... and one more time, we should NOT need to use "tablets" or do complicated procedures to have clean and good smelling laundry. As I said before, millions of people overseas use FL day in and day out, without doing anything else other than 1) put dirty laundry in 2) select cycle 3) put detergent in 4) push button 5( get clean clothes out. End of the story. Kenmore, Sears, whatever, get your acts together !!

It comes down to how powerful the washing machine pump is... Now, this check valve has to have a reasonable bore, what's a washing machine outlet - 3/4" at least? The big risk here - ok there's two - one is, as Pinoke says, you might end up with sewer gas being sucked into the place, which, in a well-sealed house (as most are) could be lethal, maybe even explosive. The other risk, more likely, is a failure or blockage of the check valve which could result in raw sewage being siphoned back into your basement. If you chose this route, I wonder if your insurance would pay out if something went wrong. Don't get me wrong, provided the lift's not too great (and you'd definitely need a trap etc some distance ABOVE the sewer line to reduce the risks, this ought to work, however, and I'm not sure about whether all ejector pit things have to be buried - I've seen one of these ejector units and they don't look that complicated or expensive, and the BIG advantage is, you can have a laundry sink down there too, which will drain into one of these gizmos - and will pump itself out up into the sewer when it fills - and these things are designed for the job and ought to do it more efficiently and safely - and when you sell the house, you won't have to rectify anything, as if you take the cheap route, you might be forced to disclose it, or an adept building inspector may spot it and put you in an unfavourable bargaining position.