Friend asked me about this. He wonders, can a check valve in a Washer go bad and suck bad water into the potable water system? He uses YELLOW detergent. Yesterday he flushed toilet to his downstairs bath adjacent to the W/D. The plumbing is all underfloor. Toilet wouldn’t fill back up. He disconnected the toilet supply and saw blue slimy gunk in the valve port. After cleaning it the toilet filled properly. He’s wondering if the washer doesn’t backwash into the potable supply due to a faulty check valve???? Sounds possible to me…but he uses yellow detergent, not blue.
If at first you don’t succeed, try using a hammer next time…everything needs some extra persuasion from time to time. -ME
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Can't happen for two reasons:
1) In order to siphon gunk back into the water lines from the washer there must be a vacuum in the water lines. This is a relatively rare occurrance in most areas, and even more unlikely on the bottom level of a multi-story house.
2) Since (1) can occur in very rare circumstances, all appliances manufactured in about the past 40 years are required to include a vacuum breaker that will prevent siphoning. In fact, this is the most frequently failing part on our 29-year-old Maytag (3 times in 29 years), and when it fails it sprays water all over everything. There is no "check valve" -- the drain line is not in anyway connected to the fill line, so no way for pressure to be applied to the fill line by the washer pump.
Not sure what the slimy gunk was. Could have been just scum from the copper pipes, a blob of adhesive from plastic pipes, or the remains of a gelatin plug used when doing some plumbing repairs.
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