"Ed Pawlowski" wrote in message
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On 8/1/2020 5:12 PM, %% wrote:


"Ed Pawlowski" wrote in message
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On 8/1/2020 4:07 PM, %% wrote:


"Ed Pawlowski" wrote in message
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On 8/1/2020 9:17 AM, TimR wrote:
This isn't a problem I need to fix, just a curiosity I wonder about.

We have a sink that is used lightly. It never has the stopper in, it
is never filled, there is never a reason for it to have water enter
the overflow. The overflow hole is on the near side, the faucets on
the far side.

And yet, it has developed a tan stain obviously starting at the
overflow and extending down towards the drain.

I don't see any sign water has ever come out of the overflow, nor do
I see why that would happen, but there has to be some reason for
this.

Probably fumes from the trap and drain system.

Unlikely to be fumes if the stain is where liquid would run.

Put some water down it and flush it out and it may help.


WTF do you think is happening in that drain?

Most likely something like emptying the bath
is producing a surge up the drain which sees
some dirty water from the drain coming out
the overflow and its that the stains the sink.

You wash down all sort of caustic and organic materials

Its less clear that that is happening
much with that infrequently used sink.


Key word -- infrequently
Dirty water sits and rots.

But doesnt move out the overflow down to the drain.