I had a washer & dryer relocated to my basement several months ago and just
recently have had a flooding problem. The washer drain tees into an
existing kitchen sink drain, coming from the floor above. We rarley fill
the kitchen sink because we have a dishwasher, but the wife gave the dogs a
bath, filling then draining the sink. This caused water to pour out of the
washing machine drain in the basement below. I was wondering if an
automatic vent placed somewhere in line could solve this problem. I think
the sink itself is vented because I can see a vent pipe coming out of the
roof in it's general location. If an auto vent might help, where would be a
good location for installation? The washing machine has no problem
draining. The problem only occurs when draining a full kitchen sink.
I have created a crude illustration of the situation here:
Thanks for any advice.
I was going to say to snake the line, that your drain was partially
blocked, but that doesn't jibe with the washer draining fine.
So, SWAG no. 2. It's possible the glug of water (technical term) from
the sink is temporarily pressurizing the line enough to blow the water
in the washer leg trap out the washer stand pipe. If that's the case,
an autovent won't help...it won't open on pressure, only on suction.
A real vent would help though. Is it just a little water that leaks
out? Try adding food coloring to the water in the sink and see if the
water that comes out is clear or colored. If it's the trap water, it
will be clear.
There is no such thing as standard black PVC. There is black
I second the installation of the check valve. BUT, I would
snake out the drain first. It is most likely that you have a
restriction in the drain line which can allow for the slow
discharge of water, but backs up when the line is flooded such
as from the sink being drained. A standard 2" drain should be
able to easily handle a sink draining. Also, check the vents
to make sure that they are not stopped up, but I doubt that
they are. It is most likely a restriction in the drain.
An auto vent would not help at all as the opening of the
washing machine drain line is a vent in itself.
The washer needs a vent well below the wye inlet to the main line.
Since air is more easly displaced than water, the trap at the washer
will then hold as it should and the massive sink discharge will meekly
flow down the line. You may want to check your sink vent for blockage,
if indeed tthe vent you see is connected to the sink. Your plumbing
system already has one error, so there may be another involving the
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