# basement sink - backwater valve



## caufmantr (Jun 22, 2011)

Hello-

I have a question on adding a sink into a basement - I was planning on tying into the main drain drop from the upstairs kitchen, however I am questioning the backflow / backwater valve - can I add this to the drain line of the sink before it ties into the main drain (between the P-trap and the maindrain)? Most articles I see reference putting these valves under the concrete which i understand for toilets, showers, .... but the only thing I need to protect here is the basement sink.

Any advice is much appreciated,

Todd


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## VIPlumber (Aug 2, 2010)

Backwater valves are normally used on the main house drain before it connects to the city drains.

What you are looking for is a check valve, either swing or spring. Having said that I don't believe that it's normally necessary to install them on a simple sink drain unless there's a problem with your drains backing up? Or are you a worry wart Todd?


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## caufmantr (Jun 22, 2011)

Thanks - could be reading too much into this, but I see code requirements for a backwater valve for any fixtures that are lower than the lowest manhole cover. Trying not to have to breakup concrete and put in a typical backflow valve to the main sewer line, was hoping to have something in-line in the drain for the sink before it ties into the main vertical drain going under my slab......



Are you saying this isn't necessary either way?

Thanks!


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## VIPlumber (Aug 2, 2010)

caufmantr said:


> Thanks - could be reading too much into this, but I see code requirements for a backwater valve for any fixtures that are lower than the lowest manhole cover. Trying not to have to breakup concrete and put in a typical backflow valve to the main sewer line, was hoping to have something in-line in the drain for the sink before it ties into the main vertical drain going under my slab......
> 
> 
> 
> ...


Where are you located? That's not in my code requirements here.

If protection from backup/flow if what you're looking for, then put a check valve in your drain line.


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## caufmantr (Jun 22, 2011)

Thanks, I will likely add a check valve then as I depicted in the drawing. For reference, I am located in Michigan.

Thanks again,


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## plummen (Jan 10, 2010)

that check valve in that small line is going to play hell on you if you ever have to have that sink line cabled ,it will go through but it will be tough getting it back


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## caufmantr (Jun 22, 2011)

I should be able to put the check valve in a closet that is planned to be built around the main drain line anyways - hopefully that will help if any service is required - still sounds a lot better to me than breaking up concrete to put in a backwater valve for just a sink....


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## TheEplumber (Jul 20, 2010)

I am required to put BW valves on fixtures located below the manhole rim. On new construction I have to isolate the basement fixtures on the valve- no other fixtures can be on it. You can buy small(1.5 &2") BW valves with removable tops for your purpose. If your worried about the main backing up into your sink, put it in.


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## caufmantr (Jun 22, 2011)

Thanks, I have a bathroom pre-plumbed on the other side of the basement that has a bw valve under the slab. 
For the sink, does the bw valve have to be under the concrete or is something inline with the drain ok, per my previous sketch location? I am not really worried about backup in this area, but I am pulling a permit for the basement so I gotta do it right.....

Thanks!


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## TheEplumber (Jul 20, 2010)

caufmantr said:


> Thanks, I have a bathroom pre-plumbed on the other side of the basement that has a bw valve under the slab.
> For the sink, does the bw valve have to be under the concrete or is something inline with the drain ok, per my previous sketch location? I am not really worried about backup in this area, but I am pulling a permit for the basement so I gotta do it right.....
> 
> Thanks!


the bw valve needs to be readily accessible in the wall or floor.


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## ben's plumbing (Oct 6, 2011)

imo you really don't need this ck valve installed in system overthinking this....and if installed needs to be accessible.....I believe that is code in your area also..ben


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## #1plumber (Dec 25, 2011)

Where I am from they will not allow a check valve in line with any fixture. The back water valve has to be installed on the main line coming into the house under the concrete. And besides, if water does back, up its going to come up through your floor drain first if its not protected.


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## cicliste (Feb 11, 2018)

I realize this is an old thread but I just did this exact thing. Our basement is pretty low and I added a utility sink. Drains out through the main 4" drain. It's the only fixture that's below the level of nearby manhole covers. The sink has a 1-1/2" drain and after doing some research I decided to put a $30 backwater valve on the drain itself rather than on the 4" main drain. Works perfectly and the lid just unscrews in case it ever gets clogged. We haven't had a sewer backup but just in case we ever do, I feel a lot better know the basement's now protected. 





caufmantr said:


> Hello-
> 
> I have a question on adding a sink into a basement - I was planning on tying into the main drain drop from the upstairs kitchen, however I am questioning the backflow / backwater valve - can I add this to the drain line of the sink before it ties into the main drain (between the P-trap and the maindrain)? Most articles I see reference putting these valves under the concrete which i understand for toilets, showers, .... but the only thing I need to protect here is the basement sink.
> 
> ...


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