My reputation as someone who can solve household engineering problems has spread over the years, and so I get requests for help with all kinds of household difficulties. A recent problem involved a washer. When the wash cycle was complete, the machine was still full of dirty water. I was called in to fix it.
In order to see exactly what was happening, I started a new wash cycle. First I had to set it to the start of the rinse cycle to pump out all of the dirty water. As it pumped out the dirty water into a washtub, I noticed the washtub was draining very slowly. So I figured the drain needed to be cleared. When I started the new wash cycle, it ran correctly. At the end of the wash cycle, the water pumped out to the washtub, and the rinse cycle began with clean water rushing into the tub. Yet at the same time, water was also being pumped from the full washtub back into the washer. That was when the revelation came.
Some washers, including this one, have a flow reversing valve on the drain pump, so when the water is not supposed to be draining, the pump discharge and inlet port connections are reversed, providing for wash water circulation. That would work out very well if the drain hose was above the surface of the water, which is the standard setup.
This setup was different. There was an extension on the drain hose, which was added to prevent the discharge flow from spattering out of the tub, all over the wall, and on to the floor. That extension, combined with the tub full of water, provided a handy means to draw the dirty water back into the tub. There was no overflow, because the level switch was satisfied and shut off the clean water valve.
The same cycle would happen when it went into the spin mode, at which time it would once again pump the water back into the tub during the spin cycle. So at the end of the wash sequence, the clothes were still soaking in the dirty wash water.
The solution was simply to clear the washtub’s drain and add a small hole in the extension tube, so that the pump could not pull the dirty water in the next time the drain became plugged. The fix wound up being a lot less work than anything that I would have needed to do to the washer.
This entry was submitted by William Ketel and edited by Rob Spiegel.
William Ketel graduated from Lawrence Institute of Technology as an electronic engineer and quickly got involved in the testing area of automotive engineering at Chrysler. At Sun Electric, he learned controls and instrumentation engineering. He also picked up mechanical engineering and machinist skills and developed a love for designing industrial testing systems. For fun, he rides his bicycle and participates in ham radio activities as N8QVS.
Tell us your experience in solving a knotty engineering problem. Send to Rob Spiegel for Sherlock Ohms.
Yet again, our Sherlock Ohms notices something out of the corner of the eye that reveals the problem is not what it initially seems. Sherlock Ohms assumes nothing. Sherlock was called in to fix a washer, but when the water is not draining well, the problem may be with the drain path and not the washer.
The symptoms here sound a lot like those in an earlier Sherlock, where the culprit turned out to be a water fill level sensor for the rinse cycle, if I remember right. That earlier Sherlock had the same solution as our own washer's fill problem after rinsing. I admire the determination to find the solution in both of these, since the symptoms are apparently identical. It sure took us a few tries to find the right answer.
Maybe it's time for Maytag or Whirlpool (or other appliance manufacturer) to pen an article for Design News. Give them an opportunity for rebuttal, however I'd ask you to lay down firm ground rules. They'll be writing to engineers and designers; simple (dumb) sales propaganda will not be tolerated. If they can avoid that, you might find some interesting discussions result.
In the early '70s, at least one manufacturer offered a syphon break kit which was acted much like this fix. It was used when the vent groove that was molded into the end of the rubber drain hose was blocked or when the drain was 'hard connected' without the vent. In addition to allowing air into the drain line to break a syphon, it also prevented the pump from sucking water back into washer.
The anti siphon kit would have been worthwhile if I had anticipated that as being the problem. I decided to examine the functioning first, before getting into what I anticipated that the fault would be, because moving and opening a washer is a dirty job. In this installation the siphon was due to an extension added to the drain hose to reduce the spatter of water out of tyhe washtub.
I did see an installation of a washer in which the drain hose was run straight down to a drain in the basement. IN that setup the problem was quickly obvious in that the washer would never stop filling, and yet never fill. An anti-siphone "tee" at the upper end solved the problem for that installation.
Probably the newer front load washers will have a different set of failure modes.
My washer, in the basement, pumps the drain water up to a standpipe connected to the large drain leading to the septic system. Occasionally, if the septic tank (more likely the pipe leading to it, as the tank had been recently pumped) backed up, the washer drain hose would syphon the contents of the sewer pipe into the washer when the washer stopped. Yuck! What a mess to clean up and sanitize! I suspect that the problem is roots in the sewer pipe, but can't get at them at present. So, I made up a check valve assembly using PVC plumbing components; this was tightly sealed to the top of the standpipe. Now, the washer pump injects the water into the sewer pipe, but backflow is eliminated. Needless to say, I check the washer tub before starting a new load, in case of a check valve failure.
In many urban (& suburban) Plumbing Code jurisdictions throughout this "fruited plain", there are specific requirements that when a clothes washer or a basement bathroom effluent is directed upward to a soil line, there MUST be a check valve in the line to prevent precisely this occurrence. Even lawn sprinkler systems which are connected to a "city" water supply MUST have anti-siphon valves in line w/ the supply line.
I guess I am not sophisticated enough to see this problem. Every washer I have ever connected went into the sewer line. They go up to a pipe, which is attached to a wall and then through an elbow to the sewer. Seems simple enough and I do not have any idea how that sewer water can get back to my washer.
If there is no water backed up in the sewer pipe your washer drain will work fine. But if you have standing water in the pipe--as was the situation with the sink--water can get sucked back into the washer. An antisiphon unit blocks water flow back into the washer and bleeds in air instead. As one comment noted, many communities require this type of antisiphon, or backflow preventer. We have them on outside faucets and on our in-ground irrigation system. Our town requires annual testing of the backflow preventer on the irrigation line. We don't want water from yards (insecticides, fertilizers, weed killers, etc.) siphoning back into our cullinary-water supply.
From Dell / Intel® New Paradigms in Design Work Scott Hamilton, vertical market strategist for Dell Precision workstations, 5/2/2013 3
Early in my career, I worked as a draftsman and remember the days of drawing on vellum with numbered pencils and Mylar with plastic lead. This was a fun experience in the sense that I ...
I've been using workstations for more than 10 years and love finding ways to get more performance from my system. With demanding professional applications that require more power each ...
A lasting memory from my first job as an engineer in an auto assembly plant is standing on hard concrete at six in the morning, vending-machine coffee clutched in hand, listening to ...
A quick look into the merger of two powerhouse 3D printing OEMs and the new leader in rapid prototyping solutions, Stratasys. The industrial revolution is now led by 3D printing and engineers are given the opportunity to fully maximize their design capabilities, reduce their time-to-market and functionally test prototypes cheaper, faster and easier. Bruce Bradshaw, Director of Marketing in North America, will explore the large product offering and variety of materials that will help CAD designers articulate their product design with actual, physical prototypes. This broadcast will dive deep into technical information including application specific stories from real world customers and their experiences with 3D printing. 3D Printing is
To save this item to your list of favorite Design News content so you can find it later in your Profile page, click the "Save It" button next to the item.
If you found this interesting or useful, please use the links to the services below to share it with other readers. You will need a free account with each service to share an item via that service.
Tweet This
4 
