Oak tree leaves and "copper" staining

[AndyTN]

I started to get a few TFP Experts off topic from another post I started and it is a long-time issue which I would like to get some opinions. Matt (JoyfulNoise) made some good comments in my other thread and it isn't that I don't trust him but I'm just looking for some additional info so I segregated it from my other post.

When I bought my house 4 years ago and we have about 8 large oak trees which the leaves get into my pool constantly. The previous owners were on their way out of the house and left us a massive problem with what we thought were copper stains from the oak leaves. When we signed the contract on our house, the pool looked like the first picture with the pool perfectly stain free. After 45 days of the previous owners not cleaning out any leaves, the pool looked like the 2nd picture as soon as we moved into the house. The stains were removed (temporarily) with ascorbic acid and tests by a pool guy and Leslie's all pointed to a lot of copper in the water.

I don't know how so much copper could get into the pool in 45 days when they were barely putting in any chemicals and the deep end had a mountain of leaves in it. I never got rid of the stains completely until I had a new liner put in and my Polaris is still stained from it. Even after I would completely lift the stains with ascorbic acid and do a ~75% water exchange, the stains in a slightly lighter shade would always reappear when I brought the FC levels up.

Matt's response from my other thread is below and the tannins make sense. Given, I don't have a clue what chemicals the previous owners used but non of the metal tests indicated iron, only copper. The Memphis city tap water also does not contain any measurable amounts of iron. Any other opinions on the situation so I can help prevent in the future?

Oak tree leaves leave brown stains from tannins. Elevated chlorine levels will slowly oxidize and remove tannin stains.

If ascorbic acid removes the brown stains then it is almost always from iron (which would not be at all unusual for water in Tennessee).

Copper leaves brown stains that don’t lift with ascorbic acid but typically get darker. Copper is not usually found in terrestrial water sources but typically comes from the use of metal based algaecides and “multi-purpose” chlorinating tablets.

 

[jblizzle]

I stand by Matt's response.

AA would make copper staining worse, so while there may be copper in the water from some unknown source, it was not causing the staining.

 

[AndyTN]

So let's assume the test results for copper in the water are just a coincidence, would tannins from oak leaves disburse evenly on every surface touched by water as in the picture I posted? Also, it was stated that the tannins stain would be broken down by chlorine but the ascorbic acid immediately lifted the stain and the stain precipitated again once I increased the FC level.

Tests at the time were indicating no iron in the water and only copper so I am going off of memory from the past 2-4 years with the problem. If the stain was actually from iron, how else would iron enter a pool other than the water source? My local utility company's water analysis states our water in Memphis only contains 0.03 ppm of iron.

I have a brand new liner which certainly fixed the stain on the liner but I can still see the stains inside my skimmer and on my Polaris. I'm just trying to prevent this from coming up again in the future. I have continuously used CU-lator packs and Metal Free proactively ever since.

 

[borjis]

I get just a slight bit of staining on the skimmer mouth and inside the skimmer at the water level.
A bit more annoying than a problem. I have to get close and look right at it to see.

What I do is use a magic eraser to clean it off, then I don't see it again until 1 or 2 years later.
weird. no idea why, but that's how I deal with it. You should be able to do the same to your skimmer
and polaris to keep them clean looking.

Same type of municipal water source, allegedly no metals, yet every other year when I add chlorine
on opening day the water get's slightly green on the deep end side and I have to swap some water out
alleviate it.

 

[JamesW]

It looks like iron, not copper.

All water from the ground has iron.

Tests for iron in city water are done at the water distribution starting point. Water traveling through the pipes can pick up iron on the way to your house.

Tests of pool water are usually unreliable. In many cases, most of the iron is in the form of stains and not in the water.

Typical copper and iron tests are not very accurate.

What copper level did the water test at?

Bottom line, it's probably iron.

 

[AndyTN]

Iron seems to be the most likely cause of the stain after reading all of these responses. The tannins stains from leaves, which I've looked up pictures on the internet, seem to be clustered right around the leaves and not evenly dispersed around every surface of the pool.

It could have been that the iron was trapped on the surface of the pool and did not show up in any test results. I released the surface stains with ascorbic acid and copper was detected but no iron. After the initial acid release, I always did a big water exchange and never really tested iron after that, just copper.

The copper test from the original stain w over 3 years ago so I'm trying to remember but I think it was 2 to 3 ppm. It sounds like the ascorbic acid would not release the copper stains like I'm describing so that may have just been a coincidence.

The first thing I do when I open the pool is dump in two bottles of Medal Free and put in a Cu-lator pack to be proactive. I have no stains with the new liner and I intend to invest a little bit to keep it that way.

Thank you for the responses.