Washing machine plumbing question

Our washer and dryer were previously in the kitchen. I installed french doors and am moving the washer and dryer to the new laundry area about 8 feet away in a closet. I have the hot and cold lines ran which are pex. My question is with the drain pipe and venting.

I planned to copy the p trap and standpipe dimensions exactly since I know they are up to code. The previous set up went from the p trap then dropped 90 degrees through the floor, exited out of the floor at a 45 degree angle, made a small run and straight into the drain line. There was no vent pipe exiting through the roof. This drain line is tied into the kitchen sink line which is vented. Is this correct? Can I just run a new section of drain pipe straight into the line like it was previously?

It is in a straight line from the old set up but the pipe will be about 7 feet longer total. The drop will still be 1/4 per foot.

Probably not, but we would have to see a drawing. Your description is too vague, and it sounds like the original installation may NOT have been to code.

Mine looks like this but without the vent. The new line drops under the house and then connects into the 2" drain line that the sink also ties into.

The drain cannot turn down without the vent going up. It never met code.

Thanks. So I definitely have to add a vent. Should 1.5" pvc be sufficient?

It's funny we never had any problems with this for 4 years. We move the washer and I start googling and it looks like it was never done correctly despite using a licensed plumber and having it inspected. Now I want to make sure it is right.

Are there any restrictions on bends in the vent? I need to run it around a beam. Also what height above the roof should the vent extend?

Thanks again for the help.

1.5" is fine. The vent can turn once it is above 42", and any section not vertical must be pitched to drain. It must be routed so that no part of the line can trap liquid.

What would be the thoughts on adding a AAV? This was the suggestion by a plumber at the distributor when I was picking up supplies. He also suggested that I could run the stack up 42" and not through the roof as long as the pipe is exposed? Is this true?

Here are some additional pictures. One show the setup I am thinking of using. I would like to vent to the outside but a aav valve may have to be used.

The others show the underside of the house. This is the last drain into the line. The vented kitchen sink drain hits the pipe about 2 feet away from where the washing line enters. You can see where the washer was previously ran. We capped this temporarily until the washer is ran.

It is pretty common to connect vents together in the attic space so that it is not necessary to make multiple penetrations going out through the roof.
Several 1-1/2" or 2" vents could connect to a larger existing vent stack going out through the roof.

cacher_chick said:

It is pretty common to connect vents together in the attic space so that it is not necessary to make multiple penetrations going out through the roof.
Several 1-1/2" or 2" vents could connect to a larger existing vent stack going out through the roof.

Click to expand...

The previous washer location was under windows. The line was cut to install french doors. The only line connecting to the vent is the kitchen sink. The new location is in an area that has a ceiling lower than the attic so connecting to the kitchen vent is not possible.

Under certain situations, an AAV can "simulate" a stopped up drain, and if that occurs, the washer will overflow, but this condition would NOT occur if the vent is run through the roof.

A sticking aav valve is a concern. There were never any problems with draining even with the unvented drain. The washer is a front load and high efficiency so it's not a ton of water. The drain will be placed above the height of the washer to help some with drainage.

I can not figure out how to vent to the roof or tie into existing vents. The roof is a shed style and lower than the rest of the attic. There is a structural beam in the way.

I know this is not ideal but it has to be better than the prior setup.