Black Tar - NOT Black Algae

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.
Pool Newbie
Pool Newbie
Posts: 1
Joined: Tue 05 May, 2009 13:01
My Pool: 16 x 36 inground vinyl pool. no heater
Location: Long Island, NY

Black Tar - NOT Black Algae

Postby lskul60 » Tue 05 May, 2009 13:27

Been having a very unusual problem for the past 12 years. This year has zero explanation.

I Live in New York, with an Inground Vinyl Pool, no heater. All chemicals properly balanced, and usually very clear water, with no signs of green algae or any other cloudiness.

I get this black, tar like buildup inside my skimmer housings. It's a semi-circle crescent in shape, at the water line and is obviously a buildup from the water being drawn into the skimmer.

For years, I had assumed it was black algae, but could never make it go away. So, I typically take a stiff brush, coated with a thick, bleached based household cleaner, and clean it off every few days. It keeps coming back throughout the season - year after year.

this year, I just replaced my liner, and the pool was freshly filled in mid April. within hours of turning on the equipment and starting to balance the alk, the ph, the cyan, adding chl and shocking, etc. the buildup was starting to form. The outside temperature has been in the 50s, there is no way I can possible have algae, can I ?

The only other thing I can thing of, is that the black is actually little particles from the inner walls of the black pvc plumbing lines. But this has been so much, and for 12 years now, that I would think my piping would be detroyed by now - if in fact, it was the deteriorating plumbing.

thoughts? thoughts????


Black Tar - NOT Black Algae

Postby dgrandrud » Wed 17 Jun, 2009 13:31

I have had the exact same tar like substance in the skimmer housing for 3 years now. It is very greasy and difficult to clean. I'd also like to figure out what it is and how to get rid of it.

Can anyone help?

Black Tar - NOT Black Algae

Postby Craiger » Tue 30 Jun, 2009 16:02

I have the same thing! I used undiluted metal stain remover on it, and it was removed nicely. It really is black algae tho I think. Only other suspect is if you have adjustable jets, there is a black foam sponge in there that may disintegrate?
Larry T.

Black Tar - NOT Black Algae

Postby Larry T. » Mon 13 Jul, 2009 09:08

I have the same black stuff. It started as a yellow, so I thought it was yellow algae. This morning, it has turned to black. It is sticking to the walls, forming in foam on top of the water, and is VERY gummy. I am wiping it as it forms and skimming it off the top of the water using a fish tank skimmer. But it is sticky and oily.
D. Donovan

Black Tar - NOT Black Algae

Postby D. Donovan » Tue 08 Sep, 2009 20:38

We have seen the same greasy black tar substance in our skimmers and in an 8 to 10 foot section along our liner, right where the water line is. Unfortunately, it attacks the ink in our liner and removes it after being in contact for 2-3 days. Rubbing the goo with your finger using light pressure also removes the ink. We are on our 3rd liner in two years. We performed FTIR analysis on the goo and it turned out to be plasticizer, which is used in the manufacture of pool liners to keep them flexible over time. Apparently, it migrates from the liner into the water and then floats like an oil. There are several sites out there discussing the phenomena. However, they don't mention ink removal of the liner at the surface. We are now in discussion with the liner manufacturer GLI as our last liner only lasted a week!

Has anyone else see the tar form on their liner and if so, did it remove the ink?

Black Tar - NOT Black Algae

Postby mikejaz » Sun 01 Nov, 2009 22:34

plasticisers are also used in your suntan lotions. i have the same build up in my skimmer, and i'm quite sure that is what it is, since we lather the kids in it every day.

Black Tar - NOT Black Algae

Postby mikejaz » Sun 01 Nov, 2009 22:38

sorry, forgot one point. the black color is the collection of dirt in the lotion.

Black Tar - NOT Black Algae

Postby Bob/H » Sun 28 Mar, 2010 12:46

Same problem: old liner/brand new liner and water. No total solution but using a "scum ball" device in skimmer and skimming the water off the skimmer water surface shortly after filter turns on in the morning helps eliminate much of it. Remove the "scum ball", run filter for awhile and you will notice the black slime gathering on the water surface in skimmer. Scoop off the surface water before the scum attaches to the skimmer walls. Good luck! P.S. We never use lotions/blocks.

Black Tar - NOT Black Algae

Postby jman » Sat 28 Aug, 2010 11:52

I have the same problem except I have a concrete pool built in 2006. I did notice a black buildup in the skimmers over the years but only this year took note of it because it was scraping off onto my skimmer basket as I was taking the basket out. I wiped most of it off today so I'll see how the buildup progresses from this point forward.

This tar/grease-like stuff must be from something other than liners only. I can't see this as being black algae, although this year I had major problem with green algae buildup in pool no matter how many chlor tabs or shock or algaecide I put in (I couldn't get chlor levels above .3 all season), but that's another problem I'll have to search posts about.

Anyone else with ideas?

Black Tar - NOT Black Algae

Postby Guest » Sat 28 Aug, 2010 12:06

Now I've been reading that black algae is tar-like and hard to remove because its roots extend into the plaster or grout. I do have some dark grey spots in my plaster but they don't feel tar-like and why would the black algae appear on skimmer walls made of plastic. I still doubt the tar-like stuff is black algae in the skimmers.

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