2-inch drain line backflow preventer?

I own a rental property that has a basement with a laundry sink, and I am wondering if there is such a thing as a drain line backflow preventer that I can install in the laundry sink drain line to prevent sewage from backing up into the sink and overflowing onto the basement floor.
The idea would be to prevent sewage from backing up into the basement if the main sewer line ever gets clogged (which has happened a couple of times in the past). My thinking is that if I can prevent any backup through the laundry sink drain, then any sewer clogs in the future will just overflow at the curb vent by the street in front of the building -- and will not back up into the basement.
When I do Google searches for sewer backflow preventers, all I see are devices that are for a 4-inch main sewer line. Here's a YouTube video example of one type of 4-inch backflow preventer that I see online:
http://www.youtube.com/watch?v=FMBznnNV-ss
.
But that is not what I want or need. All I would really need for this application is a backflow preventer for the laundry sink which has a 2-inch drain line.
Does anyone know of a drain line backflow preventer that is made for a sink drain such as a laundry sink?
Thanks.
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Those common check valves are used on water SUPPLY lines, not waste lines. They are designed to open with some reasonable amount of water pressure which isn't likely going to exist in a waste water line, unless it has a lot of head. I would also expect that even if it did partially open it would get clogged before long.
Here's a link to one source for 2" waste backflow valves:
http://www.ndspro.com/images/stories/pdfs/sewer-and-drain/diverter-and-backwater-valves-catalog-listings.pdf
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wrote:

Ah, good point. Yes, you DON'T want a check valve.
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On 10/27/2011 2:30 PM, tim birr wrote:

That's very true. In most cases, sewers backup very slowly. And as the water moves the wrong way, the flap in a check valve, allows water to leak by. It happened to my a few years back. When I went to the basement, the laundry tub was full, almost to the top and showed no signs of stopping ... although its rise was very slow. I took a garden hose, attached it to the faucet and put the other end in the sump. The faucet was turned on, and when the water started flowing into the sump, I removed the hose end from the faucet, with the water still running. I then plunged it into the almost full sink. A siphon was started, which removed most of the water from the sink. At this point, the pressure differential across the check valve was high enough to keep the flap sealed and no more water came in. BTW, a 2" ball valve could be used to close the drain line, but of course, it is manual.
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Art Todesco wrote:

I was thinking of that idea before it dawned on me that there may be an automatic back flow preventer that I could use instead. When I was thinking of the ball valve, my thought was that the tenant who uses the basement almost never uses the laundry sink. However, the washer does empty into the sink. So, I thought that maybe I could set the washer up to empty directly into the sewer line up high (not via the sink) at a location that is above the curb vent level out front. I would of course need the washer to empty through a trap first to prevent sewer gases from backing up into the basement. Then, I thought I could put a 2 inch ball valve in the sink drain line and tell the tenant to only open that when using the sink, and then close it when done. He is motivated to do that because he actually does use the basement area and has experienced the sewer backups into the laundry sink and then onto the floor in the past..
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snipped-for-privacy@optonline.net wrote:

http://www.ndspro.com/images/stories/pdfs/sewer-and-drain/diverter-and-backwater-valves-catalog-listings.pdf
Thanks. The 2 inch backwater valve may be something that would work. I can't quite tell from the website exactly how it works -- meaning what the internal mechanism is. Maybe I can check one out in person at a local plumbing supply place that I use and see the internal mechanism etc. I'll bring a printout from the link you provided so they'll know what I am looking for.
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Ron wrote:

Just use the 4" sewer rated device and adapt it to/from 2" with a couple dollars worth of fittings.
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Pete C. wrote:

I did think of that, but I was wondering if there isn't something else available that is the right size etc.
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On 10/27/2011 11:55 AM, Ron wrote:

YOu will probably get more information if you use the term BackWater Valve.
Here is one that offers it in 2" - no affiliation!!! : <http://www.siouxchief.com/Drainage/ResidentialDrainage/BackwaterValve/DWV-Backwater-Valve.YUC70
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tim birr wrote:

Thanks. I had been thinking about using a check valve, but as you and others later pointed out there can be questions about whether that would work.
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Here's one that's meant to work in a floor drain but I suppose it could be plumbed into the sink drain plumbing.
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On 10/27/2011 11:55 AM, Ron wrote:

I wonder whether you have done a thought experiment to ask what will happen if the laundry sink doesn't overflow. If you eliminate the pressure relief that the drain line gets from the laundry sink, is it going to overflow somewhere else instead?
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Matt wrote:

Interesting question. I was all set to write back how my plan is designed so that if there is a backup the overflow will come out of the curb vent and won't back up into the laundry sink and basement.
But then it dawned on me -- duh -- what if the blockage is in the main line before the curb vent? In that case, the backup would be into the 1st floor apartment tub and toilet and then, of course, would overflow into the 1st floor apartment. That has me wondering if there is some other plan that I could figure out.
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