Help determining maximum sink depth I can put in

[sankarnkp]

We currently bought a home and it has drop in sink on granite countertop. We are replacing the whole countertop and also putting in an undermount sink. As I look more into the plumbing I am concerned and lost on how to determine the correct sink depth I can put in.

I am attaching some pictures. The current drop in sink is 6.5" deep with a disposer (Insinkerator evolution). In the current setup, the top of the drain pipe is around 14.5" below the granite base. So in my understanding for new installation I should have Sink Depth + Garbage disposer drain depth (let us call this D_installation) <= 14.5. I understand that D_installation should be as low as possible, but in extreme cases if it is close to 14.5" it will still drain. Is this correct assumption?

In case I cannot find a sink that meets this requirement, I want to get the opinion of experts here on how they think the plumbing behind the drywall is. In the pic you can see where the drain enters drywall. Around 6" below there is a clean out plug. So I think the way the plumbing is as shown in the schematic attached. Do you think the drain is tee'd into a vertical sewer line? If so I can cut the drywall and drop whole drain assembly a couple of inches down. I need your advice on what you think is the plumbing behind the wall before I tear up the drywall.

 

[frodo]

what is the current height of the center of the drain pipe from the floor?

17" or less,,you should be fine.

one thing i did notice, your dishwasher drain hose,

attach it to the bottom of the sink, to one of the sink clips. to drain correctly and so food will not back up into the dishwasher

it needs to be looped up

also... Double KUDO's on the Fire extinguisher

 

[frodo]

?


to figure out the exact height of drain

you need to know the model disposal you are using
you need the drain opening measurement on the disposal
you need to know the height of the pipe coming out of the wall from floor to center
you need to know the top of cabinet measurment

you need to know what sink you want, need the bowl debth

i usually rough in my drains at 17'' floor to center, handles just about any situation

 

[Zanne]

Are you planning to re-use that disposal? If so, be careful with the snap ring. When re-installing the unit, you have to put something on top of the flange in the sink to hold it down (or have someone press down on it for you), and hold things out of the way while simultaneously pulling the snap ring open (gently) just enough to get it to snap into place. I say you need to do it gently because the damn ring can bend and be ruined. The part itself is about 0.36cents to 0.50 cents but the shipping is $10 to $15.

You can cut the drywall and lower where the horizontal pipes meet the vertical pipe (I think maybe so long as they are still above the 17" mark).

I can't help but notice the electrical outlet under there-- is that a GFCI outlet? It doesn't look like it from here, but I could be mistaken. If it is NOT, then you need to replace it with a GFCI outlet.

I guess your homework assignment is to measure the height of where the pipes go into the wall from the floor (not the bottom of the cabinet-- but the actual floor).

Frodo, is the 17" from floor a code requirement? I can't seem to recall.

 

[frodo]

no, just tried and true measurements

kitchen sink 17'' at 8'' off center
bath lav 19''
w/h 6'
washer box 36''
toilet 12''
tub steel 14 1/5
fiberglass 16''
LOL......

 

[donald_w]

I can't help but notice the electrical outlet under there-- is that a GFCI outlet? It doesn't look like it from here, but I could be mistaken. If it is NOT, then you need to replace it with a GFCI outlet.

Around here, an outlet under a sink like that would normally be switched and on two separate circuits for the garbage disposal and dishwasher, so a GFCI outlet would not work and should not be used. GFCI breakers would work.

 

[KULTULZ]

Opening up a can of worms here...

The latest NEC Regs stipulates GFCI and in some instances AFCI on these circuits. It all depends on which years(s) NEC your local jurisdiction is following and the actual interpretation(s) of code by locality.

 

[frodo]

Kultulz. the plug is for the dishwasher AND the disposal

since they both have to have a separate circuit.

2 . gfi's will not fit in that little box.

so, they get a gfi breaker

ju got it now?

 

[KULTULZ]

Kultulz. the plug is for the dishwasher AND the disposal

since they both have to have a separate circuit.

2 . gfi's will not fit in that little box.

so, they get a gfi breaker

ju got it now?

According to the latest NEC, they want the GFCI(s) at the point of use for easy compliance with monthly testing and as a matter of convenience (not having to go to main panel for reset) (and reasoning cost of breakers vs receptacle).

There are several interpretations of this and even electricians argue the interpretation(s) amongst one another. Add to the confusion as how one inspector is going to view it over another.

Nowhere is it mentioned how he has the receptacle wired.

I personally would want both hard wired under there as a receptacle and plug are subject to too many damage variables with the way most people store things in a sink cabinet.

 

[frodo]

Nowhere is it mentioned how he has the receptacle wired.

.

look at the first picture and the 2nd picture.

you can clearly see the grey cord leaving the plug, going to the dishwasher

and you can see the black cord going into the disposal

No, I can not see the wireing in the box.

couple things I know
they both have to have seperate circuits
they both have to be GFI'd
the disposal has to be switched

I deduce, the gfi is in the breaker box

deduce'ing is like assuming, it can bite you in da butt

 

[KULTULZ]

look at the first picture and the 2nd picture.

you can clearly see the grey cord leaving the plug, going to the dishwasher

and you can see the black cord going into the disposal

No, I can not see the wireing in the box.

couple things I know
they both have to have seperate circuits
they both have to be GFI'd
the disposal has to be switched

I deduce, the gfi is in the breaker box

deduce'ing is like assuming, it can bite you in da butt

frodo

My post was in response to this post-

I can't help but notice the electrical outlet under there-- is that a GFCI outlet? It doesn't look like it from here, but I could be mistaken. If it is NOT, then you need to replace it with a GFCI outlet.

Now I made the mistake of not quoting it in my response and it seems to have created a little confusion.

I seriously doubt either of the circuits (DW - GD) are GFCI as the install was most likely made well before the current GFCI requirements.

Now take your pack off, stand easy and smoke 'em if you got them...

 

[sankarnkp]

Thank you guys for all your help. It was very informative. Here are some answers:

- The drain is 21" from the floor (not the cabinet bottm but the floor). So that means I can bring it around 4" down. That makes life so easy. Now my only concern is if it is possible to predict the plumbing behind drywall. Mainly if the drain is tee'd into a vertical drain, I could just lower the whole drain assembly. However if the drain is elbowed and the main drain is going horizontally to meet the main drains somewhere else, then it will be a very hard job to lower assembly. Seeing the cleanout cap below the drain makes me think that there is a vertical sewer.
- The electrical outlet is switched. One goes to disposer and the other goes to dishwasher. I haven't looked at breaker panel, but would guess it is GFCI brkr.

If you guys also concur that the drain tee's into a vertical sewer line, that gives me confidence to go ahead and move the whole assembly.

Once again thank you all for your suggestions.

 

[sankarnkp]

I will be getting a new Insinkerator evolution (currently it is the same one, but I just noticed it is leaking) disposal which has a 6" from top of disposer to the drain outlet

 

[Zanne]

Thanks for correcting me on the GFCI thing. I was not aware that garbage disposal and dishwasher could not be attached to the same breaker. I need to learn more about electricity and the various outlets. I was just remembering that plumbing code mandated a GFCI outlet near water. From the picture I thought it was just a regular outlet.

Sankarnkp, I hope the pipe in the wall is vertical rather than horizontal.

 

[KULTULZ]

Thanks for correcting me on the GFCI thing. I was not aware that garbage disposal and dishwasher could not be attached to the same breaker. I need to learn more about electricity and the various outlets. I was just remembering that plumbing code mandated a GFCI outlet near water. From the picture I thought it was just a regular outlet.

If you are referring to me, it is well above my pay grade to correct anyone...

You merely mentioned the outlet(s) should be GFCI (which with codes updates should be) and it made me think of the difficulties electricians are having interpreting the 2014 NEC.

 

[Zanne]

If you are referring to me, it is well above my pay grade to correct anyone...

You merely mentioned the outlet(s) should be GFCI (which with codes updates should be) and it made me think of the difficulties electricians are having interpreting the 2014 NEC.

You and Frodo both had helpful info.

I wonder if it would work to just have two GFCI outlets under there or to have one outlet wired to 2 different circuits (but that might not be easy to show to an inspector).

 

[frodo]

I have an idea.

if, the existing drain is to high when you get ready to hook uo the sink.

switch the co with your drain.

 

[Zanne]

Hmm.. Frodo, you just made me think of something: If the cleanout is directly below the drain in the wall, it is likely that the pipe actually *is* vertical there. But switching the cleanout with the drain might work.

Also, found this image and wonder if its right or if its BS.

 

[KULTULZ]

I wonder if it would work to just have two GFCI outlets under there or to have one outlet wired to 2 different circuits (but that might not be easy to show to an inspector).

This is where it gets sticky...

You can't split a GFCI receptacle but can split a regular duplex receptacle. The GFCI(s) (code now requires the DW and GD to be on separate 20A circuits) would then have to be upstream at the breaker panel or (interpreting the 2014 NEC and any local AHJ) somewhere at the counter top and/or within the sink cabinet.

Code now wants an emergency disconnect for the DW and there are many possible interpretations on that.

On top of this, the circuit(s) have to also be AFCI.

 

[frodo]

Hmm.. Frodo, you just made me think of something: If the cleanout is directly below the drain in the wall, it is likely that the pipe actually *is* vertical there. But switching the cleanout with the drain might work.

Also, found this image and wonder if its right or if its BS.

I only use the 90 if i am not hooking up a sink also

or using 2 traps