Triple Sink: disposal backwash and noise

During our remodel we has a triple sink installed. We put the disposal on the right sink and now have some problems.

When we turn on the 1-hp disposal, sometimes the ground up food makes its way into the center and left sink. Also the disposal is very loud as you can hear the noise coming out of the other two sinks drains.

The guy who connected the plumbing basically used a common horizontal pvc pipe to connect the right and center sink with a horizontal t-connector. This then connects to a vertical pipe coming down from the left sink (another t-connector is used). Then it connects to a trap and goes to the “out pipeâ€.

I’ve been researching how to fix the problem. Most likely the installer did not use baffle T connectors. So I guess by replacing the T-connectors this will fix the backwash problem.

I’m wondering if there might be a better way which will also help with the noise.

What I am considering (which I have no idea if it’s a good idea or not) is to use a triple cross connector that all the sinks could feed into and then put a trap after the connector and then go into the final “out the house†pipe.

Any thoughts? Help needed ...

Posting a picture of the current drain installation would help us help you.

It looks like you need the baffel tee in your hook up, I normally run two drains in that situation that puts the disposal on its own line and keeps them from crossing over; I guess thats too late. I would not use a cross on your system, that could lead to stoppages.

As far as the noise is concerned you have to get the disposal with the extra insulation, I don't know what you can do now, sorry.

Here is a picture...it's a bit different than I described.




Also, the disposal is supposed to be very good...it's the 1 hp WasteKing. I think the sound is so bad becuase there is no baffel.

I'm having the installer come back out to redo it. I might do it myself over the weekend if the installer drags his feet.

It's pretty easy to see how the disposal can shoot food over and up to the left sink.

Is 2 traps the way to go? Place 2 traps in front of a Y connector which feeds into final "out" pipe?

shacko said:

It looks like you need the baffel tee in your hook up, I normally run two drains in that situation that puts the disposal on its own line and keeps them from crossing over; I guess thats too late. I would not use a cross on your system, that could lead to stoppages.

As far as the noise is concerned you have to get the disposal with the extra insulation, I don't know what you can do now, sorry.

Click to expand...

Two drains meaning add an additional "out" pipe? Yeah I can't rip out drywall or tear apart the back of the cabinet at this point. We just got to the point where we are using the kitchen.

bmcgin said:

Here is a picture...it's a bit different than I described.

View attachment 10359


Also, the disposal is supposed to be very good...it's the 1 hp WasteKing. I think the sound is so bad becuase there is no baffel.

I'm having the installer come back out to redo it. I might do it myself over the weekend if the installer drags his feet.

It's pretty easy to see how the disposal can shoot food over and up to the right sink.

Is 2 traps the way to go? Place 2 traps in front of a Y connector which feeds into final "out" pipe?

Click to expand...

1: The baffel has nothing to do with sound, they are used to stop spill over when a disposal is connected to a sink with multiple bowls.

2: From your picture it looks like the drain from the disposal is going up!, if this is true you are going to have major probs. with your system.

3: It looks like the drain comming thru the wall is too high to start with, should have been lowered when the system was installed.

4: Your only way to help your situation now is to run two traps, one from the disposal and one hooking up the other bowls.

5: If you decide to run two traps make sure you don't run them toward each other.

6: I think you have to decide if a plumber put this in or you were using someone that can't spell it!!, sorry for the negatives, luck

I mentioned to the installer that it didn't look like it was draining downhill. He brushed it off as if everything would be ok. I'm glad you pointed this out.

The installer is not a certified plumber, he's a friend of a friend who could use the extra money. I thought I would do him a favor and run the risk of it not being 100% correct.

He said he will come back and take a look at it again. I want to be able to give him concrete instructions as to how to fix it.

Here's another picture....

shacko said:

4: Your only way to help your situation now is to run two traps, one from the disposal and one hooking up the other bowls.
5: If you decide to run two traps make sure you don't run them toward each other.

Click to expand...

My wife just yelled at me about the disposal backflow...better get this thing fixed.

When you say don’t run the traps towards each other, so that means the traps should run front to back? How would you recommend joining the two traps back into the single drain?

Thanks again for your help.

bmcgin said:

My wife just yelled at me about the disposal backflow...better get this thing fixed.

When you say don’t run the traps towards each other, so that means the traps should run front to back? How would you recommend joining the two traps back into the single drain?

Thanks again for your help.

Click to expand...

If you could post a picture that shows the whole hook up of all three sinks I can geve a better answer.

As soon as I get home I'll post some more pictures. My installer friend is tied up this weekend, so I may have to take a shot at doing this myself. I’m thinking that this will be a fun project if I can understand the guidance from this site. And it just might work correctly. If not, oh well not much lost, there's always plumbers standing by ready to charge $90 /hr. This project sounds fun.

I went to the local plumbing supply store bought a bunch of parts. He’s not sure if the setup will pass code.

He said to put a double wye with a clean out in the horizontal position on the drain at the wall. (this gets glued). Then glue in the connectors that allow the standard under sink plumbing to screw to it.

Then on one branch of the wye put trap that feeds the left and center sink. These sinks should connect just like a regular 2 sink setup.

On the other side of the wye have another trap that feeds from the disposal. Use the 90 degree turn down out of the disposal and drop right into the trap.

He wasn’t sure if the double wye with the clean out in the horizontal position would pass code.

I’ll get more pictures in a few hours.

more pictures

He used the wrong tee between the left and center sink. Thats a tee for a end outlet waste. If you replace it with a center outlet tee with baffles in it, it should solve your problem.

John

The tee for the center sink is a simple slip joint tee with NO BAFFLE in it, and the one to the left of it is a baffle tee, but he has it in backwards The water from the left sink has to go THROUGH the baffle, and then make a "U" turn to go do to the trap. There is NOTHING right about this installation. Why was the disposer installed in the right sink? The center bowl is made small for the disposer. There is nothing to keep the disposer drainage from entering the middle sink through the tee, and water going to the trap is "split" by that diverter tee, and half the water HAS to go into the left sink.

Dang, that's pretty good. I didn't think any of the t connectors had baffels. I just took the it apart. You're exactly right!

My wife wants the disposal on the left sink unless it absolutely has to go in the middle. Since she does most of the dishes, I’m good with it.

My installer friend said he can come over Sunday to fix it. I want to take a stab at it. I don’t think I have the right parts tonight…here's what I just bought:



(i have 2 wyes because the plumbing supply store only had the 2", HD had the 1 ½â€)

So all I need is to get a center outlet tee with baffles? It still seems like food will backwash up the middle sink.

Here’s the 4 ways which I can come up with:

Way 1: Connect the center sink to the left sink with a vertical tee. Then have the left sink join to the right sink with a center tee with baffles. Then drop to trap.

Way 2: Connect the left sink to the center sink with a vertical tee. Then connect the center sink and right sink with a center tee with baffles. Then drop to the trap.

Way 3: Connect the left and center sink with a horizontal baffle tee then connect into the left side of a center tee. Connect the right sink to the other side of the center tee.

Way 4: Have 2 traps that feed into a horizontal double wye with cleanout.

Are any of these on the right track?

This is a straightforward case of why handymen should not be hired to do anything plumbing related! You should have hired a plumber to do this properly in the first place, now you wasted more money buying materials, you've upset your wife, and the "installer" probably won't refund your money.

Your proposed "installation method #4" is very wrong, and the cleanout fitting is unnecessary as that is the purpose of the union-ptrap.

If I were doing this install, I would not use those horrible non-dwv slip joint fittings, and I would pipe this completely different as to your other proposed methods.

Unfortunately, the noise problem is something you are going to have to get used to. You have a powerful unit there, and the only way to block the noise would be if you had properly plumbed separate traps.

This is a case of playing it by ear, because WHAT and HOW you do it will depend entirely on how the space works out. The ideal situation would be to use the "Y" and connect each drain with its own trap, but you may not have room to do that. Otherwise, connect the left sink to one opening with its own trap. Then connect the disposer and center sink together with a "disposer continuous waste", (which you do not have yet). Put a cleanout fitting into the unused opening in the "Y". You have a LOT of unnecessary parts, and most are unusable for your installation. At most, you only need two traps, a "proper" continuouse waste, and a spigot cleanout adapter. The alternate way, you need three traps and two flanged tailpieces, (and the disposer elbow he might have thrown away). I could probably install the drain system in less time than it takes to tell you how to do it. The reason for putting the disposer in the center sink is that is why it was made small. It is not useful for anything else, and putting it there frees the other two bowls for other uses, such as putting water in them. Why did you use a three bowl sink if you were really only going to use two of them?

Thank you so much for the help. This is a case of handyman gone wrong. The granite counter top fabricator recommended him. He’s says he does about 3-5 a week and he just happens to be the father of one of the girls at work. So it was hard to say NO even as he charges the same as a plumber. Getting my money back is not going to happen. I’m stuck with either taking a shot at it, waiting for him to come Sunday or getting a real plumber.

And I’m not sure if I called in a licensed plumber that he would get it right. That’s why I came here. I want to be able to talk about the approaches outlined here.

As far as why we got the 3 sinks, it’s a new thing for us. We have the cabinet space, it was $165 on ****. It looked pretty cool. It’s actually is very useful. I put used glasses in it. I guess it can be used for cleaning vegetables. Putting the disposal in the center would work pretty well. My wife likes the disposal on the right because when cleaning pots all the junk can right down the disposal.

Anyway…back to the mechanic of the install.

There is enough room to install 3 traps and I do have the disposer elbow. If I can get the union ptrap and the thicker connectors, this sounds like the way to go.

As far as all the extra parts, I always buy more and return what I don’t need. If I can get the parts, I might take a stab at it today. This isn’t going to look pretty

Seriously thanks for the advice. Working on this today will a fun change.

"union P trap", "thicker connectors"? That sounds like you are going to go down the wrong road again. You HAVE the correct "P" traps, you just need a third one, OR the proper continuous waste.