Cast Iron Sink Excess Enamel

I'm looking for advice on hooking up my brand new cast iron kitchen sink. It's an undermount double-bowl which my counter contractor put in. Now that it's in under the counter (installed on rails) I am trying to hook up a garbage disposal to the smaller bowl.
The problem is that the enamel process has dripped down through the sink drain on the disposal side and has a bump approximately 3/16 inch below the sink drain opening. How can I get a good seal under these conditions?
The part that hangs down is only an inch to an inch and a half long so there is a noticeable bump below the bottom of the sink drain opening. I don't want to do anything to remove the enamel that could expose the cast iron and allow a rust out spot to start forming before the sink even begins to be used. Anyone ever encountered these problems? Is this something quality control should have caught at the factory, or is it just a trivial problem? I'm a plumbing newbie so I just don't know which way to get around this problem at this point.

Disposal manufacturers make deeper flanges, sold separately as an accessory.

Is it a Kohler sink?

Unsure about the washer/mount

Yes it's a Kohler sink. I've ordered a costly disposal flange (antique brass) which I'm picking up today. I hope it will be deep enough to avoid the problem as mentioned above.
The flange I'm replacing goes very deep, but then the part that clamps the flange to the sink and secures the disposal goes right against the sink bottom. Will a thick rubber washer do the trick here? That sounds like a vibration nightmare. The only thing the replacement had between the underside of the sink and the mount was a cardboard type (probably fiber) washer.

Picture This

Here is a picture of the whole mess. Note that's not light shining through the drain, it's the light colored enamel caught in the camera flash.

plumb confused said:

Is this something quality control should have caught at the factory, or is it just a trivial problem?

Click to expand...

Yes and no. I'd ask Kohler for a new sink or a solution.

sink

For an undermount sink that is already tiled or marbled in? The bottom of the sink does not contribute to the sealing other than to act as a clamping surface. If you use an ISE disposer, for example, with bolt anchors they will create the proper pressure to hold the disposer in place without leaking. A disposer with a locknut type mount, however, would probably leak because of the asymmetric pressure

Not worth the paper...

Kohler admits that this one is messed up, will replace it with a new onw. At least they say so on the phone. My supplier confirms this and says no problem. Kohler also claims the enamel cannot be removed or ground down since it will develop cracks or hairline fractures eventually causing problems.

The real problem is Kohler won't pay for a reinstall of the item. They claim it's not in their warranty to pay for such, and even if it was the sink never should have been installed. Well my counter installer is good, but guess what, he's not a plumber! He doesn't even care what the bottom of the sink looks like, he works with the top surface and mount. I don't think it's reasonable for him to determine that the sink is defective, but that is what Kohler implies. I think Kohler could definitely improve their quality control.

My counter guy is sending around someone to look at this tomorrow, I am indeed considering just grinding down or cutoff with a dremel tool. We'll see.

What I am also considering is an extra rubber washer between the metal top plate of the dishwasher disposal and the bottom of the sink, offset around the enamel piece hanging down.

As it is now I cannot clamp to the bottom of the sink with the bolt anchors, because the top metal triangle that clamps up on the sink bottom will only fit askew, not even close to horizontal. There is just too much hard enamel there.

Update

I just fitted an old basket rubber washer into the space between the sink and the top metal clamp. Plenty of room available to put the snap ring in place. I just had to cut the inner half of the washer out in about a 2 inch wide strip. Now the real question is, will this be bad for vibration? It's hanging on a cast iron sink so it seems pretty sturdy. Anyone know if this will be an acceptable way to hang the disposal?

Try it and see. If it doesn't vibrate it shouldn't be a problem. If it is, you may want to build up some points on the rest of the drain flange with some epoxy to help level it out and give equal clamping pressure.

Jason

Thanks

Great idea Jason, Thanks!

Because it's cast iron I'm hoping vibration won't be a problem here.

Also thanks to HJ, Mikey an srdenny for your help here. I'll post some more of what I find out later.

Meanwhile I'm just wishing I had inspected the UNDERSIDE of my sink before I had it installed. Crazy me I thought KOHLER would have done a better job of not shipping sinks with visible defects. A word to everyone else may help save you some grief also.

drain

The triangle piece does not have to fit in a horizontal plane because all it does is provide a surface for the clamping bolts to press against. So it would have been fine even though skewed. Did this sink come from HD, Lowes, or similar. If so it reinforces our argument that they get defective products that our suppliers never do. It should not have left the factory, but all of their printed material that comes with their products advise that you inspect for problems before installing it. It is a CYA thing, for cases such as this.

hj's right about cya product checking. That said, I have to admit that had your sink been one of mine, I probably would have missed the defect as well.

semi-solved sink situation

Well the bump is smoothed down now, sanded/filed to even with the cast iron so we shall see. My counter-top guy said he has seen this once before, much worse than this one was. I ordered it from a large regional plumbing supply dealer with a couple of nice showrooms locally. They were ready to stand by the product with a new one even before I talked to Kohler. It definitely helps to deal with the right companies! My counter guys were also great, but I think Kohler should be quality checking their products, not counter installers who aren't serious plumbers.

Might it be a good idea to use some enamel repair paint to just touch it up in that area before installing everything? Might provide a little insurance against any cracking / rusting etc.

Excellent

Great Idea about the brush on enamel! I had already forgotten that in this long drawn out process. Thanks for the help on that.

paint

The bottom of the sink is not coated with enamel and thus the entire rim of the porcelain coating meets a raw cast iron surface eventually. So if rusting can occur and damage the finish it has a lot of places to start.