Downstairs kitchen sink fills when upstairs shower is draining

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Old 03-09-13, 07:09 AM
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Exclamation Downstairs kitchen sink fills when upstairs shower is draining

Hi,

I have an unusual issue with my drain. My upstairs shower and my downstairs kitchen sink share the same drain and roof vent. When I run my downstairs dishwasher or my kitchen sink at full water volume, I have no problems with the sink drain but when the upstairs shower is running and especially when the same upstairs tub is draining, the kitchen sink would fill almost to the top and sometimes overflow. I would like to know what would cause that?

I snaked the kitchen sink with a 1/4 inch 25' snake and I think I hear the snake go up the drain towards the upstairs not down. I also snaked the upstairs shower drain with the same snake and nothing came out. Do I need to go to the roof vent with a longer snake? I am confused. Please help.
 
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Old 03-09-13, 12:36 PM
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You have a blockage somewhere downstream. Would have to do some calculations on how much water the tub holds vs how much water a 2" pipe would hold vs how soon the sink fills up to determine where the blockage is.......or see if you have a clean-out somewhere in either the basement or crawl space. Some homes have the clean-out in the yard somewhere on the way to the street. Not sure the age of your home or the makeup of your drain pipes.
 
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Old 03-09-13, 02:16 PM
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More info

Thanks for your reply. On the same floor as the kitchen sink is a washing machine and another bathroom with a toilet and a sink. The toilet and sink in the bathroom on the first floor never have any drain problems. The washing machine is downstream of the sink and below the p trap behind the washing machine is what looks like a 2" cleanout. The washing machine is maybe 20 feet from the kitchen sink. I don't have a basement. So why do I need access to the cleanout? Do I run the snake upstream from the washing machine from the cleanout towards the kitchen sink? Also right outside the front door is a 3.5" cleanout. My house was built in 1982. Or do I get a 1/2 drain auger and disassemble the kitchen sink drain and run the larger snake from there? Please let me know. I don't have the larger snake yet.
 
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Old 03-09-13, 02:36 PM
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It would seem that you need to snake between the kitchen sink and the clothes washer area.
You may not be able to snake from the cleanout at the clothes washer back towards the kitchen.

You will probably have to take apart the kitchen sink plumbing and go from the way.
 
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Old 03-09-13, 04:10 PM
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Stopper and fill up the kitchen sink with water. Remove the exterior cleanout cover. Un-stopper the kitchen sink and with a flashlight, look into the cleanout and observe how the water flows. If it runs fine initially and then slows, the blockage is away from the house. If it only trickles then the blockage is toward the house. You may want to flush a toilet first or run the bathroom sink to have something to reference as far as normal flow vs restricted.

House build in '82 should have PVC I would assume throughout.

Do you have a garbage disposal by chance? I've seen where blockages have occurred due to over usage of the disposal and food scraps not having enough water to push the waste on down the line.
 
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Old 03-10-13, 06:51 AM
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more info

Hi, We don't have a garbage disposal. I'll open the exterior cleanout sometime today. I think I understand now. This issue has nothing to do with the shower upstairs. The clog is not directly below the kitchen sink but further down stream. My guess is that the clog is somewhere between the kitchen sink and the clothes washing machine. The washing machine has a large volume of water and never overflows. I tried using a stopper and filled the kitchen sink to the top. Then I let the water drain. I heard the water flowing fast for about 7 seconds and then the rest of the time the water went really slow meaning that the clog is further down the drain. By the way the section of pipe from the kitchen to the clothes washing machine is about 12 feet and then to the exterior cleanout is about another 8 feet. I tried opening the 3.5" exterior cleanout but it looks like it is rusted shut. It has a rather large square fitting on top. I used a plumbers wrench but could not move it. Ugh!
 

Last edited by vinny121; 03-10-13 at 09:50 AM.
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Old 03-10-13, 11:36 AM
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My upstairs shower and my downstairs kitchen sink share the same drain and roof vent.
It cant..... Thats a wet vent...Not to code and would not be piped that way.

Have you always had this issue or is it new?


 
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Old 03-11-13, 06:30 PM
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As far as I know, this has been happening for years but I recently have become frustrated with it and more aware of it since it has overflowed the kitchen sink a few times in recent years. It always gets better after I snake the drain. What I mean is that the kitchen sink fills about a 1/4 to 1/2 the way up when the tub is drained upstairs. If a purchase a 1/2" by 50' snake and run it from the roof vent, it it possible to remove the clog? It's about 30 ft from the roof vent to the kitchen sink. wet vent I went in the attic yesterday and there is one roof vent for the house plumbing with a branch to both the upstairs shower and the upstairs toilet.
 
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Old 03-13-13, 06:36 PM
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Interesting. For some reason, when we were using the washing machine, the drain behind the machine overflowed. This is good news? Maybe the clog is further downstream. Anyway, I snaked the drain through the cleanout below the p trap behind the washing machine and this time finally clumps of hair came back out with the snake. I filled the kitchen sink and waited for the water to drain. It drained a littler faster than usual. I ran the washing machine and it drained properly again!
 
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Old 03-13-13, 08:15 PM
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knew it all along..... Glad you are seeing progress. Have we filled the tub up and done the big test yet??????
 
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Old 03-16-13, 11:36 AM
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The kitchen sink fills as before

Yes I filled the upstairs tub and had the same issue as before. The kitchen sink fills like a bubbling spring. During all my snaking, this has remained constant. Since the sink wall is to the garage, I wonder if I take apart the wall in the garage, I could install a cleanout maybe with a plumber's help? I am not sure what to do next. Maybe that will allow me access to the clogged drain?
 
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