posted March 03, 2004 07:05 AM            

Click for photo (10910 Bytes)

posted March 03, 2004 08:30 AM            

We always comment that the sink will need to be replaced. Very few times have I seen a patch hold up on these chipped or rusted areas.

posted March 03, 2004 09:20 AM            

Joe

posted March 03, 2004 08:26 PM            

The overflows are either spot welded (the old way) or siliconed (the new way) to the bottom of the metal sinks. When water gets between the overflow and the sink bottom, it rusts, which pushes up on the metal sink bottom, which then pops off the porcelain enamel.

Look carefully at the overflows under the sinks (probably will not have to look very carefully once you've looked at one) and you will see the leakage and the rust. Any rust means is it leaking, if not *out from* the joint, it is leaking to where it should not be, hence the rust.

posted March 05, 2004 04:05 PM            

It's from the overflow under the sink. Bend down, look at the over flow, you will see it rusting.

That rust pushes up agains the bottom of the sink, popping off the porcelain enamal surface, which then rusts.

Nothing has to be dropped into the sink to cause that.

Overflow pattern under sink matches rust pattern

posted March 05, 2004 05:54 PM            

Porcelain enamel, when done properly (and this sink might have had a weak spot due to poor quality control), is stronger than the rust. Therefore, the rust, if there was any prior to the damage, will push in toward the overflow space (air) rather than breaking through the porcelain. Air is far weaker than porcelain.

Something dropped in the sink, however, can create that minute crack that will allow the rust to push up, but usually it's from rusting directly under the porcelain rather than from rust in the air space.

Remember that the iron is rather thick, all things considered. Therefore, for it to rust from inside the overflow drain space and push up and break the porcelain is unlikely. It is more likely that someone dropped something in the sink (happens quite often) which damaged the porcelain enamel, allowed water underneath, and voila! Chips. And if the people were there a long time, and never took care of the initial damage, and continued to drop things in the sink, additional damage.

Considering all the chips here, it's probably a combination of initial damage followed by rusting underneath the porcelain enamel.

Even if one bends down and looks at the overflow drain in the sink cabinet, one is only looking at the bottom of the overflow drain. On top of that drain bottom is air space and then the top of the air space and then the porcelain enamel. See the Figure.

Figure
Click for photo (10579 Bytes)

It’s unlikely that rust at E is going to travel all the way through D, C, and B, to push up against the porcelain enamel A. However, if A is damaged, water penetrates through the porcelain enamel to the iron layer B, and starts to rust, causing additional damage through rusting and additional weakness to the iron substrate base of the porcelain enamel. Porcelain enamel is actually quite weak and needs a very firm substrate in order not to crack. If you’ve ever installed a porcelain tile floor, you’ll understand that. Just go look at an improperly installed porcelain enamel tile floor. If that base is not there or was not installed properly, those porcelain enamel tiles will crack just thinking about them. Same thing here. Once the substrate base for the porcelain begins rusting, a simple push on the porcelain sometimes is all that is necessary for a chip to pop and more chips to continue to pop. One doesn’t even have to drop anything in the sink once the initial damage is done and not repaired.

If this is a very old sink, Jerry’s scenario could occur simply because everything is rusted, including the bottom of the overflow drain space and the inside of the overflow drain space. But this sink doesn’t look old enough for that to have happened. Porcelain enamel also wears out. I have a sink in my kitchen where we have taken so much steel wool to it over the years to clean it that it now has no porcelain enamel left on it. Time to replace it.

By the way, when I was doing porcelain sink and porcelain-enamel sink renovation, we commonly found that the rust that Jerry is talking about is caused by storing caustic chemicals in our sink cabinets. Rarely is there significant rust in the actual overflow drain air space. Here’s a standard paragraph that I put in my reports to help my Clients understand that sink cabinets are the incorrect place to store caustic chemicals. This is from the "In Plain English" section of my reports, so it is kind of chatty for the layperson; the Realtors and Clients love it.

Quote
Sink cabinets and chemical storage—Think about what’s typically located in your sink cabinets: the underside of metal sinks, garbage disposal metal casing, copper water supply pipes, and plastic or metal drainage pipes. Plastic and metal are affected by corrosive chemicals, and continued corrosion and rusting can eventually result in leaks. Most people, though, store everyday chemicals in the sink cabinets (see Illustration 1).

Illustration 1
Click for photo (46606 Bytes)

This is the absolute wrong place to store such items because most cleaning chemicals by their very nature are corrosive. So, do not store chemicals in sink cabinets. Additionally, children won’t gain access to harmful and dangerous chemicals. And no one ever takes all those chemicals out of the sink cabinets to inspect the cabinet floor and the water and drainage pipes—unless they’re moving, a significant leak is noticed, or a child is injured after gaining access to the chemicals. Water supply and drainage pipes should be monitored regularly, and here’s how to do it virtually on a daily basis with no effort at all on your part: Store dry materials (towels, bathroom tissue, boxes, etc.) in sink cabinets (see Illustration 2).

Illustration 2
Click for photo (38093 Bytes)

This type of storage allows one to check for leaks in sink cabinets each time something dry is removed. If normally dry materials are wet, check for leaks or deteriorated caulking/grouting around the sink and countertop, and have a qualified plumber repair or replace any plumbing components or have the deteriorated caulking/grouting repaired. So where should you store such chemicals? A high cabinet in the garage or at an exterior location is great, but if you must keep them inside, an upper hallway closet, the cabinet above the microwave oven, or the cabinet above the refrigerator make great interior locations.
Unquote

Hope this helps everyone.

posted March 05, 2004 11:55 PM            

I have serviced rentals for 24 years.
They usually have steel tubs, kitchen sinks, and lavatory sinks.
The only fixtures that exhibit this behavior are the lav sinks with spot welded overflow tubes.
The other fixtures chip, but they do not spread out much from the original chip.
I have never seen this in a cast iron sink except where damaged by an outside force (and it still does not make the same pattern).
The pattern in these sinks always follows the path of the welds.

Further evidence was observed when I lived in a cheap studio apartment. I was sitting on my couch watching TV when I heard the sound of breaking glass. I went into the bathroom and saw dime sized porcelain chips on the counter. The places they had exploded from were not rusted.
The rust that forms between the two pieces of steel expands and exerts enough force to flex the steel to the point that the porcelain shatters from the surface of the steel sink.

posted March 06, 2004 07:34 AM            

Maybe I should qualify my statements.
I am seeing this in steel sinks about 15 years old.(not very old in my opinion)
The damage forms as two parallel lines running between the drain and the overflow hole. In iron sinks and steel sinks without overflows, I see chips, they just don't follow this pattern. (see doctored photo)

Click for photo (31201 Bytes)

The only time I'm wrong about something like this, is when I am...

Tim Lorenson

posted March 06, 2004 12:22 PM            

As I said, Jerry's scenario is possible. Based on my experience in renovating and refurbishing porcelain and porcelain-enameled sinks, though, I just don't think it's the case here. Of course, Joe could go back out and get some pictures of exactly how the overflow drain space lined up and we might be able to put this to rest.

Nah, then we wouldn't have any fun.

By the way, if you have any porcelain or porcelain-enameled sinks that are in bad shape and you don't want them any more, send them down this way. There's a booming market here for renovated and refurbished porcelain and porcelain-enameled sinks.