Not that cleaning the main sewer line is a bad idea, but how exactly is that supposed to cause a house to flood during a heavy rain? If the municipal sewer system gets flooded out, then seems having a clear path would be just as bad as having a partially blocked path into the house. The only way I can see it happening where the partially blocked line makes a difference is if you have either rain water or sump pump water going into your sewer system. That isn't the typical case, it's not even allowed here.
onnected a Y hose fitting to the drain pipe and ran both hot and cold at f ull pressure for 20 minutes. Max total flow would be less than the 15 gal/ min of the washer pump. Normally cold alon is 6 gal/min and hot is 4 gal/m in, so I'm guessing the total was 8-9 gal/min. I did not hear it backing u p in the stand pipe.
en sink and it was clear for the 25-ft length of snake I have. Then I ran the hose directed into the cleanout and the most it would handle without ba cking up was 3-4 gal per minute.
sharp turn around 12 feet in, which is about where I would expect the main line to be. No resistance in the pipe in that 25-ft.
et it sit overnight per instructions. This morning I flush it with hot wat er for 5-10 minutes per instructions. Then connected hot and cold back up to drain and ran another 20 minutes.
w the floor. When in and out with it and pulled out a very small amount of lint each time. Kept doing this until there was no more link coming out -- total was not enough to slow the flow. But never did get past that ben t.
r 1/2 hour, then flushed out with hot water again.
e which is too much of a job for me.
new drain pipe out the wall to an outide sink plumbed back into the drain.
If the blockage is in the main line, then you're on borrowed time. Why would you want to Band-Aid that instead of fixing it before the toilets are pouring out into the tub, onto the floor, etc? Did this ever work correctly? If it did, then it's not because of 1 1/2" pipe versus 2" pipe, a design flaw, etc. It's because there is a blockage accumulating somewher e. And it almost alwasys continues to get worse over time.
Regarding Draino and similar, I've tried that many times on various problem s with very little success. I gave up trying to use it years ago.
"I was wrong about the draining.... the washer drains into a blind standpipe - no vent up above. Below is a p-trap, although I could not get the snake to get past it."
So, maybe if you go up on the roof, you wouldn't have direct access to where the clog is.
What size and type of snake are you using? I find that they have to be thin enough to make the necessary turns, but thick enough to be able to push them into and through clogs etc. I am guessing that 1/4-inch may be too flimsy, but I don't know what the next size up is and if that would work better or not.
Another option may be trying one of these rubber bladder devices that connect to a hose and expand inside the drain line to make a seal, and then use water pressure to try to blow out a clog:
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Home Depot and Lowes etc. also have them.
I think it is probably just a clog in the 1 1/2 inch line since it used to drain okay, and that you don't need a larger drain line than the 1 1/2 that you already have.
Good luck. Hope you get it.
P.S. Do you have a curb vent or other similar vent outside that goes down to the main sewer line coming out from your house?
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