Stop Valve for Sink Drain in Basement

Hello-
I'm adding a sink in my basement. The basement is already prepped with an available 3" drain pipe in the floor.
Since the sink drain is at the lowest point in the house, I'm concerned that if the sewer ever backs up that the sewage will come up out of the sink and into the basement. So, I'd like to put either a ball valve or a check valve on the pvc drain pipe to prevent back- flow. Is this done at all? If so, what can anyone recommend. The drain is 1.5" but the floor currently has a 3" drain pipe. So, I guess I'll need some type of adapter to do that as well. Any advice on that would be appreciated too.
Thanks, Clocker
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snipped-for-privacy@blah.com wrote:

PVC ball valves readily available. Will it be remembered to close?
If you can put a horizontal run in, put a check valve like used for sump pump.
Neither of these are commonly used on waste lines.
Is there a floor drain anywhere in the basement? If so, that probably connects to the san sewer and would be a much bigger threat.
Jim
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Thanks for your reply. There are floor drains in the basement but I believe they go to my sump pit and are not part of the sewer system in my house. I will try to get a ball valve.
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--- I will try to get a ball valve.
Just curious....why are you opting for a manually operated ball valve instead of a set-it-and-forget-it check valve?
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DerbyDad03 wrote:

valve .... why? The check valve will fail when the water rises very slowly. Once the water is above the level of the check valve, the flap has no pressure on the sewer side and thus it keeps leaking, i.e. the same pressure on both sides of the flap. I had this happen a few years ago when we had a huge major rain, like 23" in 36 hours. . Even though it is illegal to put storm water into the sewers, it happens, both intentionally and non-intentionally. Anyway, when I went to the basement, at 3AM (a call from a neighbor), the water was almost to the top of the sink. I immediately started a siphon to the sump. Once the sink was close to empty, there was sufficient pressure difference between the 2 sides of the flap, and the flap shut tight .... no more water in the sink. This caused me to put in the ball valve. Have I ever closed it since? No. These storms seem to come about every 8-10 years. BTW, my floor drain DOES go in the sanitary sewer, but was stopped with a rubber compression stopper. The sewer lines under the floor are all cast iron, so there should be minimum seeping at the joints compared to the older clay tile pipes.
I complained to the town and they, not at my expense, put in an anti-backflow unit in my front lawn. It is a sort-of check valve, but is operated by a float which pushes on the flap using a parallelogram arm. If I keep flushing or running water down the drain, when the valve is closed, the sewage is then pumped, ah, forced, into the sewer line on the street side of the valve. To my knowledge it has never closed since it was installed about 10 years ago.
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wrote:

You're very lucky. A relative of mine lived in an area that had a major flood in the late 90's, and their entire (finished) basement flooded because the storm sewers backed up and somehow also backed up the sanitary sewers. I heard they are connected in some manner in order to handle flooding. (so much for poor design). Anyhow, the entire basement was full of filthy sewerage and everything was ruined. All the sheetrock walls had to be removed and all furniture and carpeting was wrecked. They had around $50,000 damage and their insurance did not cover it because it was flooding. They took the city to court (along with many other people in that city). They got nothing because the city stated that they needed a backflow valve to prevent the sewerage from entering the house. After the court case they had this valve installed at a cost of $18,000, and THEY had to pay for it. Of course the city is always right in the eyes of the law !!!!
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I'm currently using the thin wall PVC for the drain from the sink to the floor drain. It's that thinner walled stuff you see iat Home Depot that is used for P-traps and other sink drain stuff.
The ball valve I want to get is slip-slip and appears to be schedule 40 PVC. Is it OK to glue the schedule 40 PVC to the thinner walled stuff that I'm currently using for the drain?
Thanks, Clocker
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Ut oh. Looks like the 1.5" schedule 40 stuff and the 1.5" tubular PVC for the sink are different in size. !! Dammit. What do I need to do here?
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snipped-for-privacy@gmail.com ( snipped-for-privacy@blah.com) writes:
| Ut oh. Looks like the 1.5" schedule 40 stuff and the 1.5" tubular PVC | for the sink are different in size. !! Dammit. What do I need to | do here?
There are "adapters" in the sense that you can get a PVC fitting with cement or threaded schedule 40 on one end and a compression (slip) ring for the tubular on the other end. This would normally be used where the trap tubing connects to the house drain plumbing (or where the tail piece connects to a schedule 40 trap). You can also get Fernco couplers to go between tubular and other pipe types. You probably don't want to transition twice so try to use schedule 40 for everything after the valve.
                Dan Lanciani                 ddl@danlan.*com
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I've been looking for about an hour. Can anyone help point me to where I might find the adapter for going from slip to compression?
Thanks, Clocker
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Finally found one!
http://plumbing.hardwarestore.com/52-333-pvc-adaptors/female-trap-adapter-276949.aspx
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snipped-for-privacy@notmail.com wrote:

time, owned 1/2 of the sewer system in town, the other 1/2, owned by a corporation. The city had some kind of a crazy agreement with that company, that anyone who needed an anti backflow valve would get it, even if they were on the city system. I saw the bill, it was $5K, which I think was cheep at the time, 10 years ago. I probably don't need the system any more because the city put in a larger lift station, which is located about 2 block away. It's got 3 huge pumps powered by several different substations. I don't think they ever lost power.
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The OP might be better off putting in a grinder lift pump. water goes to a sealed container and gets pumped up high to a existing drain line above flood level.
will cost more than a valve but is automatic and requires no human intervention,
thats means someone will not forget to shut the valve.....
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The 3 inch line in your floor is the toilet line for a toilet in the basement and should have a backup valve on it. The line you are putting in should go to the line heading for the street or into a existing drain line in the house. Unless you don't want to add a toilet downstairs suggest you make this connection changeble in the future. Remember much easier to do right once than twice wrong. If you connect to this 3 inch above floor and there is no back up you will have to put one in the line to the drain the cheap sump pump kind don't cut it.
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I am opting for a ball valve because I think it will be more reliable. The sink will rarely be used so I will just keep the valve closed all the time except for special occasions when I'm using the sink (which is in a bar in my basement).
Thanks for your feedback everyone!
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On Fri, 21 Sep 2007 00:43:16 -0000, " snipped-for-privacy@blah.com"

Since its in a bar, will anyone be sober enough to remember to open or close the valve? <grin>
Pour me a cold one !!!!!
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