Dark Ring Along Vinyl Liner Near Bottom Of Pool Walls

by Roger

We installed a vinyl liner for a polymer wall pool. We did everything in the usual manner. We never had any hand in treating the pool water, maintenance or chemicals, the customer had a separate guy for those tasks.

The liner went in perfectly and looked great, the customer was happy. However, the customer contacted us this year (14 months after the installation) and reported a dark discoloration around the pool liner, at the bottom of the walls where the wall vinyl material meets the floor material.

Customer stated they didn't have any problems with the liner nor did they have any staining or discoloration up to the time when their pool guy winterized and closed the pool (Solid safety cover). When they pulled the cover off two weeks ago, that's when they first noticed the black ring around the lower portion of the vinyl. We went to see it, it's a dark gray/black color and completely smooth to the touch.

It wouldn't budge at all not even the pool brush could get any off. We didn't test it at that moment because we don't have any hands on experience with this sort of thing, none of our customers have ever had any staining or dark discolorations. We just learned how to test it upon reading your site.

The customer is irate because they're convinced it's somehow our fault even though all we did was install the liner just like we do any other liner and there weren't any signs of anything growing on the pool bottom when it was exposed during the installation. We've learned from your site how to test it but the customer won't let us, they're threatening to sue.

The issue doesn't sound like black algae from what I've read on here, it's completely smooth to the touch, won't flake or brush off and is only around the perimeter of the lower wall, not quite ON the seam but approx. 2in above it. Can you please tell me what this most likely could be? Metals? Fungus from beneath? They do have crappy water supply and always tons of dog feces/urine on the grass around the pool.

Thanks for the question Roger

Honestly without the chemical readings it's difficult to know what may have caused the alleged stain. The chlorine tab/ascorbic acid test would be the next best thing to determine the kind of stain it is. I assume that you may know that due to the details in your question.

Does crappy water supply mean well water? It could be metal staining. If the pool is on well water with high copper/iron content and a metal sequestrant was not used during closing it can cause metal staining. This is where the ascorbic acid test comes in. One thing about opening and closing pools is you want to close as late as possible and open as early as possible. This is July 2. My opinion is that pools should be open by late April, barring any unforeseen circumstances such as snow, freezing temperatures, or ice.

One would normally find black algae in plaster/concrete pools. This kind of algae digs itself into the surface. Vinyl is not porous enough for that. It can happen with vinyl but not likely.

Next would be mold and/or fungus or rust coming from the bottom of the pool. This can happen during heavy rains where water can seep into cracks.

Then you have dark green algae that stains the pool. This can be done away with through balancing the chemicals, shocking the pool with liquid chlorine, brushing and filtration. I've also found that baking soda and a soft bristle brush works well at removing stains on vinyl liners. The Magic Eraser works as well.

According to my calculations and the info provided I assume the liner was installed around February 2013. This would be 14 months from right now and would have been closed for the Winter. Closing a pool, if not done properly, can cause all kinds of headaches for a pool owner. And opening a pool 1 1/2 months too late is also bad. A pool is a perfect breeding ground for algae, especially when it's hot and closed up with no chemicals and filtration.

One test you can do for seams. Take some red food coloring and place it at different locations near the stain. Obviously someone is going to need to hold their breath for a while. If the seams were not properly sealed the food coloring will be absorbed into the area. If it stays in one place or falls there's no suction at the seams. If there's no suction the seam is intact. If the seam is intact then water can't escape. When water can't escape it means you did the job well. I would then look at the closing procedure the pool company/guy did or the possibility of the mold/fungus issue underneath the pool.

I understand the customer is irate. I cannot give legal advice but proper tests need to be performed to determine the cause. My opinion is they need to allow you to make a good faith effort to remedy the situation if in fact your workmanship is to blame, but, you need to perform the tests to determine that. With the information provided to me, my opinion would be a classic case of the customer jumping to conclusions.

My understanding is that many vinyl pool liner manufacture's terms and conditions do not cover what is called microbiological staining. Also, many warranties don't cover damage to the liner caused by an improper water balance which can and will cause severe damage to the liner. I'm not sure as to what affect this has on closing the pool because the water is not balanced for several months.

Also, my understanding is contractors will warranty the installation up to 1 year. If there are any imperfections in the liner this may not be your responsibility. Some terms and agreements mention the contractor does not manufacture the liner and is not held responsible for any imperfections to the liner.

Stains don't just happen. Something (outside influence) needs to be introduced onto or into something in order to get a stain. You can't wear a white shirt and then a red stain magically appear. Something red must have been introduced to the shirt. I've had customers say the chlorine in their pools keeps going up and they don't understand why. Chlorine will never increase on its own, it will always decrease due to splash out and topping off with new water (dilution), sun, heat, UV rays, etc.... Chlorine must be introduced into a pool in order to increase.

In this pool case, in my opinion, it's very difficult to have a balanced pool with proper filtration, sealed seams, good vinyl, proper installation, and no fungus/mold/bacteria and/or rust around or under the pool and then get a dark stain on the bottom. It would need to be one or a combination of the above.

The question says the customer is convinced it's somehow your fault. In my opinion the word "somehow" is the operative word. What I'm hearing from that statement is, "It's your fault. I don't know how or why but I'm blaming you without any proof and will not allow you to remedy the situation".

I've been around enough to know the customer should allow the merchant/contractor/business to make a good faith effort to fix the problem.

I would try to get a good pool guy over there to perform the necessary tests. If the customer allows or refuses be sure to document everything i.e. times, dates, locations, witnesses. Take videos and pictures if you can. This way if it does go to court you can prove you made a good faith effort.

If they refuse to allow any tests to be performed and stop you from making a good faith effort it's best to consult with a lawyer.

The aforementioned is to be used as general information and is my opinion. It should not be taken nor used as legal advice.

To post a reply, or if you have a similar question, you can see your post on the Q&A page in the "Pool Liner" category.

Check back to this post for updates or answers.

If you feel your situation is more complex than this, I do phone consultations for a donation of your choice.

Pool Consultation

Hope this helps and have a great Summer.


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Jul 03, 2014
Thank You Robert
by: Roger

Thanks for the very prompt, thorough detailed response to my original question. After spending approximately 2hrs on your site, I could tell you were a very seasoned industry pro, that's why I decided to ask you.

I uploaded a photo with my original post, I'm not sure if you received it or had a chance to see it?

I must have hit the wrong # button, we installed the liner last year in April (2013).

Like you said, the water balance and many other factors play an important role. We tried several times to obtain information from the customer regarding the maintenance history, chemicals, winterizing/closing etc., because again, we had nothing to do with any of those tasks. The customer won't even tell us the name of her pool guy, we simply wanted to reach out to him to discuss the matter, get his account of what's been happening with the pool for the last year+, put our heads together type thing.

The customer is in an area prone to ground water. Her surface drainage seems out of whack too, which we tried to tell her last year but she barely lets you get a word out before she's dismissing what you're saying ("never had a problem with this or that"). The customer also has a concrete deck where one side has sunk since we were there during the liner installation last year, water is definitely getting in through there too.

We've documented the situation and we don't have her permission to visit the property to test the black stuff so I reckon we'll see her in court.

As far as I'm concerned, I don't create the environmental factors or conditions and I certainly have not been responsible for her pool chemistry/water balance. I also didn't have any doing in her choice to leave the solid cover on her pool well into June while it's been stifling hot for 3 months now with sporadic torrential downpour. Not to mention the hot snaps we had throughout the winter in between consistent rain.

The customer has vehemently refused our help and has insisted the problem is our fault since the first day she called about it last week.

It's interesting, she won't even tell us who pulled the cover off. I can't imagine her pulling a heavy duty solid cover off by herself and if her pool guy did it, why didn't he address the black staining at that time. When we met with her she said he still hadn't come by to see it after almost 2 weeks of the pool being uncovered and her calling to tell him about it.

I appreciate your feedback and you sir, are right on the money. I'll be making a donation, your time is valuable not to mention your information.

Thank you,

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