Bathroom sink overflow hole buildup

[y_p_w]

I've been trying to clean up the overflow hole in few sinks and been having a bit of difficulty because of the design. Once I replaced the pop-up in a bathroom sink and had access to the wide overflow (away from the user), which goes into the drain. I found an old business card that turned to sludge, as well as a plastic buisiness card that was still intact. I think my kid put them in there. And it was pretty nasty as it's typically still wet but doesn't get enough water flow to flush away the buildup. I've tried squirting bacterial/enzymatic treatments in the hole. Typically foamed up with dishwashing detergent to maximize contact time to allow the bacteria colonize any buildup.

I was at my parents place and they have this sink that overlooks a window. The small overflow hole is on the user side and it looked like algae was growing where there was sunlight. I did my best to clean it but couldn't really do much more than scrape off the immediate area with some TP.

And it was particularly nasty at a store when I went into the bathroom and noticed that every single sink had black gunk in the overflow hole. It's like nobody every cleaned it nor noticed it was filthy.

Any suggestions for what to do to clean it and perhaps keep it from coming back? I've tried using bendable (wire) bottle brushes, but they were only so long and might not fit in a small overflow hole. I was thinking maybe (smoking) pipe cleaners, although maybe the best I can find would be similar chenille stems for crafting (seen them at Dollar Tree). I was thinking maybe some bleach to kill any algae, but then a bacterial/enzymatic drain treatment to maintain it. Maybe just vinegar or baking soda?

 

[Kira]

I has access to lab quality (meaning thicker and longer AND more expensive) "pipe cleaners". I has just purchased a 10 lb. bag of citric acid and it worked well.
The water at the worksite is referred to as 'liquid rock' by the locals.

 

[samven]

You can get very long brushes that look more like they were meant for a test tube but I worry that they will get caught on something and I wont be able to get them out. I have used the long heavy duty nylon cable ties like these https://g.co/kgs/8ykFWo1 you just need to work them back and forth.

 

[KGMtech]

I found the main bathroom sink was not flowing well, and once I used some Aluminum TIG rods (from 30 years ago sales job), on the overflow opening down to the main drain, the thing now drains like a champ. I will not share the colour or texture of the gunk removed.

 

[Kira]

I will not share the colour or texture of the gunk removed.

Occasionally, on competitive cooking shows, a contestant will make something which looks like what you're not describing.
The judges say, "It doesn't have an inviting appearance".

 

[y_p_w]

Occasionally, on competitive cooking shows, a contestant will make something which looks like what you're not describing.
The judges say, "It doesn't have an inviting appearance".

I took apart a P-trap once and found the drain was really slow because of a thick, black sludge. It was a thick, uniform sludge that didn’t have noticeable bits of anything identifiable. I’m guessing that it was oxidized cooking oils and fats that went down the drain.

 

[BMWTurboDzl]

I've been trying to clean up the overflow hole in few sinks and been having a bit of difficulty because of the design. Once I replaced the pop-up in a bathroom sink and had access to the wide overflow (away from the user), which goes into the drain. I found an old business card that turned to sludge, as well as a plastic buisiness card that was still intact. I think my kid put them in there. And it was pretty nasty as it's typically still wet but doesn't get enough water flow to flush away the buildup. I've tried squirting bacterial/enzymatic treatments in the hole. Typically foamed up with dishwashing detergent to maximize contact time to allow the bacteria colonize any buildup.

I was at my parents place and they have this sink that overlooks a window. The small overflow hole is on the user side and it looked like algae was growing where there was sunlight. I did my best to clean it but couldn't really do much more than scrape off the immediate area with some TP.

And it was particularly nasty at a store when I went into the bathroom and noticed that every single sink had black gunk in the overflow hole. It's like nobody every cleaned it nor noticed it was filthy.

Any suggestions for what to do to clean it and perhaps keep it from coming back? I've tried using bendable (wire) bottle brushes, but they were only so long and might not fit in a small overflow hole. I was thinking maybe (smoking) pipe cleaners, although maybe the best I can find would be similar chenille stems for crafting (seen them at Dollar Tree). I was thinking maybe some bleach to kill any algae, but then a bacterial/enzymatic drain treatment to maintain it. Maybe just vinegar or baking soda?

Spray some Tilex in there and rinse.