Tom - Mark - I need some help with this one, please.

My sister in law has a two story townhouse. The drain (4" (?)) exits on the house on the left front. Going up stream of the drain is the downstairs half bath. From there, the drain rises to the second floor washer and bathrooms.

The clothes washer appears to drain into a 1.5" to 2.0" vertical drain immeadetly above the downstairs bath.

The problem is that when the washing machine drains, the downstairs bathroom will flood by way of the commode.

Do I need to replace the entire drain pipe with a larger pipe? Or is there some other way to suppress the vapor lock that is occurring just beyond the toilet and causing the backwash?

Hey Don, Always happy to help out a fellow expert.

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is there some other way to suppress the vapor lock that is occurring just beyond the toilet and causing the backwash?

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What makes you so sure this is a "vapor lock"? Sounds like a partial blockage that's downstream from the toilet. Have you snaked the drain line either from the lavatory roof vent or from the downstairs toilet after it was pulled?
If this set up ever worked and nothinghas been added, like a new washer, then you won't have to replace any pipes, Simply snake and clear the pipes. Good luck, Tom

Tom,

There ought to be a law protecting people from in-laws!

At about 9:30 PM my sister-in-law decided to finish her wash, knowing that the washer caused her last flood. Guess what, it flooded again! What a surprise.

By the time I got there, she had vacuumed (carpet cleaning machine I loaned her) about 5 gallons of water out of her hallway carpet. I got another gallon out.

I pulled the out side cleanout cover off and received a high pressure cascade of water. So that definitely places the problem on the outside waste drain line. Because the water exploded out of the cleanout and then stabilized about 2 inches down the throat, I'm pretty sure that the problem lies between the city's cleanout and the home cleanout.

I would have snaked the line then and there, but my snake was on loan to my nephew in law (?) Any way he borrowed the snake to clear a shower drain in the master bath about two months ago. Since I babysit there, I decided I'd clear the blockage and then use my snake over at my sister in law's.

Now there was an enormous amount of crud on the drain pipe so I cleaned the throat out as best I could and still couldn't clear the blockage. Then I tried to get the snake to go down the horizontal drain and either I can't find the hole for the drain pipe, or the blockage is so thick I can't penetrate it with the arrowhead tip on the front of the 3/8" steel snake.

If you are looking at the face of a clock, 12 would point to the commode in the bathroom, 6 would point to the shower drain and 3 would point to the adjacent bathroom tub/shower drain. I tried to go the the 12 and 3 directions but without any luck. My snake bottoms out at about 12" and I can't bend the arrowhead to find the drain line.

Sorry for the above book!

I'd like to get the drain working so my niece doesn't have to stand in waste water!

First things first. Your niece has a stopped up shower that been clogged for two months and your brother has a whole house blockage. Hmmmmmm! Wonder which is the most urgent?
You'll probably locate the brothers clog out at the street raiser. Do you have a sewer machine,(see image) or a drain snake? If all you have is a drain snake do the shower first and then rent a sewer machine and do the sewer.

After rereading your complaint I see that all you have is a 3/8ths. Drain snake.
If you can't get the spade tip past the return bend in the trap reverse the cable, Put a small bend on the end of the snake and try again. Run out at least 10 feet and flush out the drain line with hot water.
Now rent a sewer machine and clear your brothers sewer. Good luck, Tom