Jack's Magic has a stain test kit to determine such things. You may want to try that to narrow down the problem.

I would also test your pool anyway to verify your the chemical content to your service company's findings..

Also, test your fill water. That's important.

I have had six pool companies run tests on the pool including the Jacks Magic tests. I have a neighbor who works for a water testing company and has tested our water..

nothing.

what I'm trying to find out is if anyone else has had this problem.

It's definitely a metal of some type in the water. A reaction between 2 dissimilar metals can also create staining. Perhaps from your water source. Different types of piping within house plumbing system can cause reactions.

Just shooting from the hip, mind you, the stain may be from silver or cobalt. Manganese can also form a black stain.

Any fertilizers being used within proximity of the pool?

What type of sanitizing system are you using-tabs, granular, liquid, SWG?

I would suggest an in depth water test starting with your source water. Test beyond "normal" things such as, pH, alkalinity and calcium hardness.

A call to the plaster manufacturer to get their input is another opinion is a good source. Perhaps they have seen this before with their product.

Mystic, different pool companies have tested for all sorts of metals. Nothing.

I have a cage around the pool so no fertilizer has gotten in. I have an Intelliflo IC40 for a sanitizing system. I also have a water report from my neighborhood that I can send you if you give me an email adress.

The plaster manufacturer is blaming the pool maintenance company. The pool maintenance company has their records for maintenance of the pool. I have cameras so I watch what the maintenance company does and there is nothing out of the ordinary. They maintain 30% of the pools in our subdivision and no one has the problem.

I can understand your frustration. I'm not surprised the plaster manufacturer is blaming the service company. This however is usually the case in my experience. Believe me, I'm not taking any sides. Your service company sounds they are spot on. Cases like this though become a finger pointing duel.

The plaster manufacturers carefully blend their materials and make them in batches. Like any other product, it's the way it's applied or installed. It's up to the end user or a service company to maintain water parameters to ensure longevity of the product..

Any chance there are trees overhead? I had a client who was certain the plaster had failed as there were black stains. Turned out to be caterpillar eggs (actually moth) from the tree above falling into the pool. Organic material can cause stains.

I know you mentioned no black algae but... We've used a product called Yellow Out in extreme cases of black or green algae and it works great. You super chlorinate and follow up immediately with the Yellow Out. The water has to be balanced a certain way prior to adding. Read directions. We don't use it often but when we do, results are good. Black algae is tuff stuff.

Is your pool salt a good quality? Free of iodine? A pure/food grade salt must be used. Not water softening salt.

I hope these suggestions will help-tough call on something I can't put my eyes on.

Nope no trees overhead. There is a lanai cage covering the pool so nothing really gets in it. Last reading was 2.0 for chlorine and 7.6 for PH. The pool salt was put in originally by the pool company and some added over the two years by the service company, No Iodine that I noted. This was the original finish (look at the seating where there is no glare)

This is the finish in November 2017

Interesting. I was visualizing random spots of black but it appears to be a much larger, consistent area. I'm at a bit of a loss. Perhaps the color pigment is fading and the darker finish is the result?? Is the discolored surface rougher than the rest?

Thats what I think is happening. This pool is only 2 1/2 years old and I'm trying to find out if anyone else has this problem?

Yes the discolored figure is rougher than normal

So no one else has had this problem?

Hi Fred, did you ever resolve this? I came across this thread as we're Considering this pebble currently....would appreciate if you're able To share an update. Thanks