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Plumbing in the Home/Kitchen plumbing connections



First, it's great that you are volunteering your expert advice for us poor sods that have to stumble through projects that we really should hire pros for but can't because we either can't afford it or are just too cheap or both!  

I had to completely gut my kitchen due to a really nasty mold problem.  I had a professional plumber rough in the water and waste but I now have to install the finish plumbing (see "too poor and too cheap" comment above!).  He has either gone out of business or left town or both, so I can't ask him what was what.  

I will have a double bowl sink, garbage disposal, dishwasher and fridge water line.  

Here are my questions:  When he roughed it in, he installed three water stubs.  Two are parallel to each other.  I presume those are the hot & cold for the sink and dishwasher.   The third stub is below the left water stub.  I think this feeds the water line for the fridge since there is no other way to get water to the fridge water valve in the wall behind the fridge.  Would that make sense (or does code require it?) to plumb a dedicated line for just the fridge instead of running a plastic water line to a double connection on the cold water valve? The lines are all 1/2 inch copper.        

The other mystery is the two drain tees.  There are two drain tees that empty into the the main drain/vent. One is about four inches above the other. Why two?  One for the sinks & garbage disposal and one for the dishwasher?  One for the left sink and one for the right sink/disposer? If I feed the dishwasher into the garbage disposal, then whey do I need two? Is this maybe a code requirement?  (I'm in IL).  I understand you have to speculate, but any clues will help me figure this out. Thanks!

air gap
air gap  
Typical kitchen sink drain layout
Typical kitchen sink d  
The kitchen sink finish is one of the "busiest" places in any plumbing system. Lots of stuff going on there.  

Hopefully, your plumber followed standard rough-in conventions.
Standardly, hot water is on the left, cold on the right. The second connection on the left side is probably a separate hot water stub out for the dishwasher. That's actually a good thing. If the dishwasher fails or starts to leak and it is fed by a dual angle stop, you also lose hot water to the sink if you shut it off. With a dedicated supply, this problem is eliminated.
By the way, a dishwasher is drained into a port in the side of the garbage disposer after passing through an air gap fitting mounted on the top rear ledge of the sink.

The second inlet into the drain stack is for a required clean out fitting. Typically, the cleanout goes above the drain inlet. When I rough these in, I usually point that one to the exterior so that is accessible from outside and you don't flood your kitchen when you open it. Think about it... It's a drain won't drain and the water is up to the rim of the sink, where is all that water going to go when you open the clean outfitting? LOL, big surprise!
I will include a picture showing a typical drain system on a sink with a disposer.

Good Luck,

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QUESTION: Dana, thanks so much for the feedback. This is starting to make sense.  

The top drain then is really a clean out.  So there, I glue in a female threaded fitting to take a drain plug?  (BTW, it is pointed inside the cabinet as the plumbing wall is an inside wall.)

If the lower left stub-out of the three water stub-outs is hot for the dishwasher (which makes a lot of sense), then that leaves the water line feeding the fridge.  I remember it was a sweated copper line to the feed valve in the wall in back of the fridge.  So that means that line is always filled with water unless I shut the water off at the main and drain the system?  

I think the old water line to the fridge was fed by a dual angle stop from a single stub that fed both the sink cold water and the fridge water.  Following your logic of a separate feed for the dishwasher, this means that if you have to shut off either the fridge water or the sink, the other will keep being supplied without interruption?   

Thanks again, Dana, you've been a great help already!

Hi Dan,
You are correct about clean out. There is actually a fitting: a cleanout adapter that is male on one end and has female threads on the other. Don't forget to buy the cleanout plug itself. The cleanout adapters don't always come with one included. Ask me how I know! LOL

As for the icemaker line, it is not uncommon to hard pipe to a shutoff valve behind the fridge. If the fridge is in the same location, you need to track that line and see if it was reconnected. If not, it will have to be re-fed somehow.

Having that original icemaker supply fed by hard piping and having a dual angle stop for it under the sink is inconsistent. That would not be the normal method. As with the dishwasher situation, a dual angle stop controls water flow to both devices connected to it. Shutting off that angle stop will shut off the supply to both. If I house has both icemaker and dishwasher water requirements, I typically installed four water stub outs on the rough. Two hot and two cold so that each device had its own shutoff valve.

While it may be cheaper and quicker to use dual angle stops to supply multiple devices, the downside is obvious when it comes time to repair something. This was a lesson I learned early on in my plumbing career. I originally learned my plumbing chops from a guy that was a cheapskate and a bit sloppy. Most of his experience was "tract" work where cheap and fast was the rule of the day. Once I started doing my own jobs (and having to be responsible for them) I soon learned that cheap and fast was neither cheap nor fast in the long run. As my daddy used to say "Why is there never time to do it right the first time but there is always time to go back and do it over?

The same philosophy applies to supplying water to the house and to an irrigation system (sprinklers). Each system should have an isolation valve to control only that system. As an example, a few weeks ago I came home to find my water shut off inside the house. It seems that the landscapers were working on the sprinkler system and broke something which caused one of the sprinkler valves to start leaking.  Not being plumbers, they just shut off the main supply line and killed everything and then left. They failed to realize that I had reworked the incoming water supply and installed a separate pressure regulator and isolation valve that supplied only the sprinkler system, and allowed the water to the house to remain on while the sprinklers were off.
Good Luck,

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Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


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