The mystery of the bathroom
September 19, 2005 10:56 AM   Subscribe

What's this blue residue in my sink and tub?

In my new apartment, I've noticed over time a visibly blue residue build up in the bathroom sink and the bath -- they're both white so it's quite obvious, but I'm not sure if it's happening in my kitchen sink. I did some basic googling and found that people talked about over-acidic water possibly corroding copper pipes and causing this, but I asked my landlord who lived in the place just prior to me and said he's never encountered the problem. Could it possibly be the soap I'm using? Why does it only seem to leave a residue in a particular pattern, instead of over the entire span of the tub? The residue can be rubbed off pretty easily, but comes back after a few days.
posted by Big Fat Tycoon to Home & Garden (13 answers total)
Copper compounds have a blue / green colour and are almost certainly due to copper pipes. They are usually quite dilute in your tap water, so a pattern is left in your bathtub where the puddles became more concentrated as the water evaporated.
posted by randomstriker at 11:21 AM on September 19, 2005

Perhaps your landlord cleaned the tub more often, removing any build-up? I don't mean to imply that you keep an unclean home. However, you said that it can be rubbed off but comes back after a few days. Maybe your landord is one of those people who cleans the tub and sink two or three times a week.

I've had blue build-up in tubs at some of my homes. I always thought it was from copper pipes. I assumed that the water pours down to the drain first, so the build up happens there -- you're less likely to fill up the tub and sink on a daily basis.
posted by acoutu at 11:23 AM on September 19, 2005

BTW, it is the chlorine in your water that is reacting with the pipes to form copper chloride -- a harmless salt of blueish / green colour.
posted by randomstriker at 11:25 AM on September 19, 2005

As an aside, I used to get pink, not blue, residue in the sink and around the rim of the toilet until I moved. It certainly wasn't the soap I was using.
posted by zsazsa at 12:13 PM on September 19, 2005

Hey, I get the pink resedue too! It comes off real easy, but I'd love to know how to keep it from appearing in the first place.
posted by LordSludge at 12:45 PM on September 19, 2005

I've always assumed the pink residue was a fungus of some kind, thus making the above suggestion to taste it shiver-inducing.
posted by smackfu at 1:12 PM on September 19, 2005

Does the residue taste like soap? Ewww.
Seriously though, do you use soap with a bluish tint? Not sure if that would cause it but it does seem possible.
posted by trillion at 1:17 PM on September 19, 2005

The pink residue is probably a type of mold. In my experience, it particularly likes areas already slightly sticky from hairspray or lotions or even soap. For instance, if I wash hair goop off of my hands but don't rinse out the sink well afterwards, I get it around the edge of the drain.

I think randomstalker's got it right. I only get the blue residue when I use bleach-based cleaners in my tub, and only under the tap where the water drips occasionally. When I switched to non-bleach cleaner it stopped. If you want to disinfect as well as clean, note that hydrogen peroxide and vinegar will also work.
posted by desuetude at 1:32 PM on September 19, 2005

No, the soap is white -- some cheap brand called Lux. It's possible that the design of the sink basin has allowed this to happen in a way that I don't notice in more normal sinks (it's some fancy-schmancy sink that has a pretty flat, graded bottom that slopes toward the drain but maybe allows water to sit further away from the drain as it dries? Doesn't quite explain the tub though, but I'll try that evaporation suggestion. It is possible that the landlord was a much cleaner soul than me -- the aesthetic of the apartment is super minimalist and more high maintenance than i would have expected so I can see him being a stickler for cleanliness.
posted by Big Fat Tycoon at 1:35 PM on September 19, 2005

Have you bought a new pair of blue jeans or blue socks recently? Anything with blue dye?

It also could be algae, is there sunlight coming into the bathroom?

That pink stuff mentioned earlier is usually bacteria that, somehow, eats the manganese in hard water.
posted by 517 at 1:49 PM on September 19, 2005

Is copper chloride really harmless? This page seems to indicate otherwise:

posted by Big Fat Tycoon at 3:16 PM on September 19, 2005

BTW, it is the chlorine in your water that is reacting with the pipes to form copper chloride -- a harmless salt of blueish / green colour.

I drink untreated well water, straight from the Albemarle County ground, which long ago turned my sink blue. No chlorine, though lots of copper pipes.
posted by waldo at 7:06 PM on September 19, 2005 [1 favorite]

Greenish blue deposits are a complex of copper (II) ions and soap residue usually. Copper can leach from the pipes when the water is soft or can be present in the water supply. The stains are often easily removed by a little soap and ammonia, and don't tend to stain porcelain the way iron or manganese will, for instance. If you want to eliminate them enitrely, you can look at getting a magnesium salt water softener installed on your house supply ($$$).

Copper chloride is pretty harmless, it's not that bioavailable. If you're concerned that your water is dangerous, get your house water checked for metals content. A local service lab can do it for you cheaply (look in the yellow pages under "water quality" or "analytical laboratories"), but some municipalities will do it for free too.

The bright pink scum really is scum---it's a bacterial mat. It happens most commonly if your water is "hard", but will happen with most municipal water supplies eventually. You remove it with any biocide (bleach, chlorine dioxide, peroxide, one of the organic peroxide "bathroom scrubbers" like Kaboom, etc..). If you want to eleminate the pink stains for ever, you'll just have to clean the bathroom more frequently, you shlub.
posted by bonehead at 7:05 AM on September 20, 2005

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