I have installed a system that “should” be fine, but when the washer drains, some water is going up (8″ above the 3 way valve) and spitting out the auto-vent.  I have a 1-1/2″ line down through the floor into the basement space, connected to a 1″ elbow and 1″ line running out to the yard where it currently connects (until I get my irrigation lines set up) to a 3/4″ hose.  I have a back flow preventer installed in that main 1-1/2″ line as well.  When the machine drains there is plenty of pressure, and plenty of water running out the hose, but even though the 3-way valve/T is 7″ above the machine tub rim and the auto-vent a good 7-8″ above that 3-way/T there is still water coming out of the auto-vent.  Could this be due to the 3/4″ hose connected to the 1″ at the end? It can’t be because it wouldn’t flow back through the back-flow valve.  What is the auto-vent for? This is not explained.  If it is to prevent a vacuum on the machine pump, if the line isn’t closed or capped at the end, why would it be necessary?  What is its purpose?

I would really appreciate your insight and help.  Thank you!



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Hi Nicki,

Short answer- you have a defected  aut0-vent. Replacing it should solve the problem. Water should never come out of the auto-vent, and if it does it means the mechanical vent is broken. (Sometimes they come defected when you buy them.)

The reason to use an autovent is to prevent a potential siphon from being formed in the line, which could drain water out of your machine as it tries to refill.

You said you have a 1 1/2 inch line coming down. I am not sure I understand how you constructed your system, because a typical laundry-to-landscape system would be plumbed with 1″ pipe the whole way. And did you use a swing check valve or backwater valve for the backflow prevention?

Depending on your machine, going down to 3/4″ hose could be adding too much friction and potentially damage the machine, so I wouldn’t wait too long to finish the system!

Hope this helps.


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