Garbage Disposal and Dish Washer off Switched outlet?

murphysfOctober 28, 2012

Garbage Disposal and Dish Washer off Switched outlet?


I currently have a garbage disposal. There is a switched ac duplex outlet in the cabinet under the kitchen sink that the garbage disposal plug into. In my backsplash there is a wall mount switch that switches the outlet. This is the original installation. Home is on the San Francisco Peninsula, ranch style built in the mid 1950s.

The kitchen does not have a dish washer. I am going to cut out a cabinet and install a dishwasher.

The issue is the power needed for the dishwasher. The wiring is original knob and tube and I am not planning on opening the walls etc. The outlet is currently switched for the disposer however I need constant power for the dishwasher.

I was thinking if I could pull a wire off the hot side of the wall mounted switch that I could break the tab off the duplex outlet I could have one of the receptacles switched and the other constant. However I am not opening the walls and there is no conduit to pull a wire as it is knob and tube.

The only idea I have is to purchase an insinkerator counter top air switch. This way I could leave the wall mounted switch in the on position all the time to satisfy the dishwasher and also plug in the air switch and control the disposer from the air switches counter top switch. Is this my best solution?

Are there any tricks or cleaver ideas that would work that I am not aware of?


Thank you for reporting this comment. Undo

You will need to rewire and have a new dedicated circuit from the panel. If knob and tube exits, it's grandfathered in but cannot be altered.

However, you really should budget for a complete home rewire and have your DW project wait until that time. I'm really surprised that your insurance company hasn't forced the issue before now. Many will not insure a home with K&T. Especially in the SF area, where they are more than a little paranoid about fire code and issues that contribute to fire hazards. Consider yourself lucky that the issue hasn't been brought up so far, but don't push your luck much further by doing any jackleg project.

    Bookmark   October 28, 2012 at 10:57AM
Thank you for reporting this comment. Undo

see also your post in kitchens forum. Below is some info (accurate except that K&T was used by builders well into the 1960s).

2008 NEC on K&T:
- Over current protection to be on hot conductors only
- Over current protection not to exceed 15 amps
- No open splices - original splices may remain if soldered and insulated with tape
- New extension wire connections to be made in junction boxes
- Knob and tube wiring to be supported only by non-conductive stand off supports - it may not be secured in contact with combustible materials
- Knob and tube wiring is only rated to be used in free air, un-insulated spaces. It is not permitted to have knob and tube wiring covered or concealed by insulation

Here is a link that might be useful: knob and tube wiring

    Bookmark   October 28, 2012 at 12:59PM
Thank you for reporting this comment. Undo

I would not even try to cut in to the K&T or add to the circuit at all. A dishwasher should usually be on a separate 15 or 20 amp circuit, I would maybe think about putting it on with the disposer if you were aware not to use them together and they were on more modern wiring. Highly suggest that you leave the K&T alone since K&T is most dangerous when it has been modified incorrectly or overloaded. Instead go get some 12/2 romex cable and pull a new circuit to the new dishwasher from your breaker panel. If your home still is using a fuse box then you need to hold off on the dishwasher project and get a new breaker panel installed first. if your homes K&t wiring is ok and not damaged or unsafely modified your electrician can just put all the k&t circuits on 15 amp breakers if your local code allows k&t to be still in use.

I am in an older home that still had some K&t when I bought it. now I have it down to only a few circuits and those are mostly just running lighting and ceiling fans that were in the house. I had to add circuits to the upper levels. I am adding a dishwasher my self very soon too and I will just put a new beaker in for it.

    Bookmark   October 30, 2012 at 9:44AM
Thank you for reporting this comment. Undo

If you have a crawlspace you can run the new circuit under the floor and use a floor-mounted outlet. That said, I don't see any reason not to break into the wall behind the DW to install the outlet there - the wall will not be visible when the DW is in place, so you don't need an undetectable job there.

Before anyone asks, having the outlet behind the DW is OK per code: "The receptacle shall be located in the space occupied by the appliance or adjacent thereto."

Personally, I'd not sleep well in a house with K&T wiring.

    Bookmark   October 31, 2012 at 7:02PM
Thank you for reporting this comment. Undo

why do you even need an outlet? around here in Pennsylvania most dishwashers are directly wired to the cable from the panel. the Romex cable entering the area low on the wall or the corner of the floor where the unit will be is usually how builders and other installers do it here. no outlet saves labor and materials.

@ PeterH K&t wiring can be very safe if it has never been damaged by improper splices and overloading. when K&T was installed new in those days you had to be very skilled to do it, more so than some are that do today's wiring. I would and do feel OK with it. Now if I found splices done buy just twisting the wires and taping in the open no I would not feel safe. new splices must be in a box done with wire nuts and all. original splices that were soldered and taped are allowed, back then splices were all to be soldered.

    Bookmark   November 2, 2012 at 5:36AM
Thank you for reporting this comment. Undo

All my kitchen outlets were rewired by an electrician and all are ground fault protected. I think you need the third wire of Romex for them. Knob and tube in older homes must be a crap shoot. I was born in SF and our home was built in 1906. I can recall blue arc fire two feet long coming from one of the light fixtures that shorted. When my dad went to the basement to check the fuses there was an arc 3 feet long shooting out. He got the fuse pulled but I don't recall how. That was in about 1938.

    Bookmark   November 2, 2012 at 5:24PM
Thank you for reporting this comment. Undo

> why do you even need an outlet?

It depends on your local code - some say that you need a way to shut off the supply that is "within sight of" the appliance. I think that's true of the OP's location. That means either a switch or an outlet. The purpose is to protect a person working on the appliance against the risk of someone turning the breaker back on. Regardless of code, I consider it good practice to use an outlet, both for safety and because it makes it easier to unhook the appliance.

Dropping in an outlet only takes a few minutes and costs about $10 (if you do it yourself).

> K&t wiring can be very safe if it has never been damaged
> by improper splices and overloading.

And the insulation hasn't oxidised or otherwise degraded over the years, and no-one has added thermal insulation around it, and no-one has bashed it while moving around in the loft, and...

The point is that there are plenty of ways for K&T (or any older wiring) to become unsafe, and it's effectively impossible to know whether any particular house's K&T wiring is still in good condition.

    Bookmark   November 2, 2012 at 6:20PM
Sign Up to comment
More Discussions
I am about to purchase a dual –fuel, 30 “freestanding...
need help - with Miele DW and Ikea Sektion panel
Hi All, Getting a Sektion kitchen. I want a Miele...
Kathy Rohde
Sealed vs Open Gas Burners
What's the difference between sealed gas burners and...
Oven Control Board bad again, 4th time. Kenmore Double Wall Oven
Hi everyone. I have a 5-6 year old Sears Kenmore Double...
Coffee Machines
What is the best built in coffee machine for your buck?...
J Saleh
Sponsored Products
iTouchless IT14SC Trashcan SX Stainless Steel 14 gal. Trash Can - IT14SC
$79.98 | Hayneedle
Waste King Legend 9940 3/4 Horsepower Disposer
Schon Kitchen All-in-One Undermount Stainless Steel 30x19x9 0-Hole Double Bowl
Home Depot
Vipp Laundry Bin
Design Within Reach
Signature Brown Car Floor Litter Bag
$6.99 | zulily
32 Spun Metal Lid
© 2015 Houzz Inc. Houzz® The new way to design your home™