:( To whom it may concern; I am trying to help a friend that lives in New Jersey while I'm here for some time on business in Florida. I will be at her house over Thanksgiving and I want to take care of a problem she is having with her washer while I'm there. She purchased a top loading Maytag washer brand new about 11 months ago when she moved into her house. She had her brother hook up the washer and after having problems for about two weeks with it they brought the machine back to the store and exchanged it for a new washer. Upon installation of the new washer she was having the same problem. This tells me there is another problem other then the washer I would think. Ok so here's the problem. She does a load of laundry and at the end of the wash her cloths are still wet and the washer still has some water in the tub. Again this is a new machine and two machines were having the same problem. After reviewing pictures she sent to me over the Internet I saw the washer drain hose go into a pipe nipple then into a trap followed by a 90 then finally into the main sewage pipe. (This washer is installed in her basement) Now upon first review my thought was the path in which the water has to travel through the trap and then a 90 was creating too much resistance/back pressure in order for the water to properly evacuate the tub in a timely manner prior to the completion of the spin cycle. The drain hose from the washer fits loosely into the drainpipe and I would think if the trap and the 90 created a high backpressure condition the water would then follow a path of least resistance and over flow the pipe in which the washer drain hose sits in and would be pouring out onto the ground. If the hose is taken out of the drainpipe and placed on the floor to drain into the sump pump the problem does not exist. The pipe in which the washer hose drains into is approximately 8” above the top back portion of the washer. My next thought was the washer's water pump is unable to push the water to that level and there maybe too much head pressure. The washer was also placed on blocks to elevate it so the drainpipe was not higher then the washer. With the washer elevated the problem once again does not exist. We obviously can not allow the washer to keep draining on the floor over using the sump pump and creating a standing water environment in her basement while causing the lower portion of the washer to repeatedly get wet and prematurely start rusting the machine, nor can we keep the washer elevated creating and unsafe condition if the washer were to fall during the spin cycle and do damage to itself or a person. I'm going to eliminate the trap when I get there in two weeks, but before I get to her house I'd like to have some info as to what the pump is capable of. At this time I'm unsure if the problem is the height of the drainpipe or the resistance caused by the trap and the 90. Possibly a combination of the trap creating high backpressure while the pump is struggling to lift the water to such a height causing the water to run back into the washer tub upon the completion of the spin cycle. Can you please give me any specs you might have on these pump and at what height they are capable of pushing the water. My next test I am going to ask her to perform is to take the drain hose out of the pipe and let it drain on the floor but keeping it at the existing height that it's already placed at when in the pipe. This will tell me if the washer's pump can handle pushing the water to such a height. I would greatly appreciate any information you can give me on this situation if in fact you may have come across this problem in the past. I'm sorry I can not furnish model or serial numbers on the machine at this time do to my location and the location of the washing machine.
Thank you
Bill

Trade washers with the lady that is having trouble with the washer pumping out so forcefully the drain over flows.

Apparently in response to problems like yours, the manufactures are making many models with more powerful pumps. Unfortunately, not all the 4' high stand pipes will take the water fast enough. Finding a model with a higher discharge pressure may be your answer.

There is an air gap where the discharge hose enters the stand pipe. If what water makes it up there, goes down the drain, modifying the drain after it won't help. Traps are required by code for good reasons. Is there anyway you can instal a stand pipe in another drain that would be lower? To make that washer work, you must reduce the height up to where it enters the standpipe.