Unidentified Dark Areas Under Tile Line

[bxcrwlly]

Dark areas began appearing in my pool around April of this year, just below the tile & water line. Picture attached as an example. Pool contractor dispatched their stain person. He said he couldn't identify. I tried several removal methods such as Vitamin C, Chlorine tabs, JM Stain Identification & Treatment. None completely eliminated the area and most played havoc with my water balance. What shows in the picture appears at various points around the entire perimeter of the pool but not in a consistent fashion. Also notice the dark blue discoloration in the grout lines of the tile. Any input on identification and corrective actions is appreciated.

 

[PJ]

Only thing I can think of is mildew or black algae/algae stain. Did your CYA ever get too high or your chlorine too low?

 

[bxcrwlly]

PJ...at the time we had a pool service, so I'm not sure what our stats were. We're in central Fla. and I believe the service may not have been keeping a close eye on things from Jan-Mar. Since May, I've been maintaining and balancing the pool myself. I haven't noticed any real change in the dark areas. I've also been advised to use a "metal control" product on a weekly basis.

 

[PJ]

It may be iron but I doubt it. What are your current readings and why are you using the metal control? .....what are the readings on copper/iron?

 

[bxcrwlly]

PJ....last time I had the water anlyzed metals were at zero. Current readings are as follows:
Water Temp 73 - During the day
FC-4
PH-7.4-7.6
TA-75
CH-225
CYA-100
Salt-3500

Running the pump 8 hours per day 7 days. The reason I'm and have been using metal control was based on recommendations of my contact at Jack's Magic. Was advised salt pools tend to have high metal content.

 

[JohnT]

My first thought is that is color bleeding from the tile.

 

[jblizzle]

The reason I'm and have been using metal control was based on recommendations of my contact at Jack's Magic. Was advised salt pools tend to have high metal content.

That does not make any sense. There is no metal in the water unless it is already in the water you use to fill the pool or you add it through the use of some algaecides or some (not-recommended by TFP) Mineral system which sometimes are part of a SWG system.

If you have no metal in the water, there is no point in using anything to control it.

Regarding your stains, is there any chance the dark spots you see in the grout are actually the mortar showing through the grout? Had this at my previous pool.

Not sure what the darkness in the plaster is, but if it is always located up by the tile, seems like maybe something is bleeding from the mortar or grout onto the plaster ... not sure that is actually a reasonable possibility or not.

 

[PJ]

No salt water pools do not have a high metal content, unless your ph was allowed to get too low and your heater parts corroded (rare in a salt pool), or your fill water already had metals in it. If you have a 0 metal reading...quit wasting your money. Your CYA is way too high....so your chlorine is not working as it should. You need to drain your pool 1/2 way and refill to get that down to 50. While your water is down try using straight bleach on the stains and a stiff pool brush. If that doesn't work try an acid wash.....but only after rinsing the bleach off very well. I can almost guarantee it is the remnants of black algae (which tends to bury itself in plaster/grout). Then refill and balance your pool. Also do not use trichlor/dichlor or stabilizer in your pool from this point on .....to shock or supplement. Use bleach or liquid chlorine if you have to shock.

 

[PJ]

Color bleeding could be a possibility.....in any case my solutions should help.

 

[jblizzle]

Your CYA is way too high....so your chlorine is not working as it should. You need to drain your pool 1/2 way and refill to get that down to 50.

Actually with a SWG, we recommend keeping the CYA between 70-80 ppm, but getting to that will still require replacing water. The problem is that the CYA test maxes out at 100ppm, so there is a chance you could be well above 100ppm which makes it difficult to know how much water to replace. Also, if a pool store is doing your testing, they seem to be particularly bad at the CYA test. I would suggest getting one of the recommended test kits and then trusting your own results. Once you have a good idea of the CYA level (possibly by diluting the initial pool sample with 50% tap water and doubling the results), then you know how much water to replace.

 

[duraleigh]

I assume the light blue area at the bottom of the pic is your waterline. Is it at it's normal position?

Beautiful tile. Did the PB put them in?

Visually, it looks like it's coming from the tile but tiles virtually never bleed so I wonder about the mastic used underneath. Did you see the tiles being installed?

 

[bxcrwlly]

Jason....my Jack's Magic contact recommended CYA at 100. We're in central Fl. so not sure if that recommendation was due to high temps(air and water) rapid chlorine loss. Prior to that, I was maintaining CYA around 70. I'm currently using a Taylor K2006 test kit.

Dave S....we drained some water to do a partial fresh refill at the time I took those pics. Normally, my water level is midway up the tile line. We built the house and pool long distance with only occassional trips to the site before it was completed. I had someone taking pics of the construction. The pool contractor did install the tile. I contacted the tile vendor and furnished pics. They said it wasn't bleeding as the ceramic tile is baked and doesn't bleed. They also contacted the tile producer in Asia who anaylized the pics and confirmed a "no bleed" scenario.

So we're looking for any insight as to possible other causes/remedies.

 

[bxcrwlly]

Dave S....addendum: The pool was completed in April 2011. The discoloration didn't appear until April 2012 and has remained since with no apparent worsening.

 

[JohnT]

Metals, particularly copper, are often used in glazes. Any chance of checking with the manufacturer again?

 

[duraleigh]

so I wonder about the mastic used underneath

Now that you have confirmed the tiles were normally submersed , I still suspect something in the mastic or "thinset" that is used to adhere the tiles to be the culprit.

(CYA of 100 is too high.....70 is correct for most SWG pools

 

[bxcrwlly]

Thanks for the responses and guidance. Appreciate the feedback from all.

 

[bxcrwlly]

Re: Unidentified Dark Areas Under Tile Line - Update 12/10/1

o.k. so I sought out a Certified Stain Specialist to make a physical inspection of my pool. He showed up today 12/10/12 and in collaboration with a surface specialist indicated the following; These are my words not theirs. The discoloration is neither metal nor algae based in cause. We conclude the discoloration is the result of an aberrant behavior associated with the plaster, mastic, or shell due to possible contamination, density or bleeding of a foreign material or object through the plaster itself. None of our standard remediation techniques will resolve this issue. In our experience, the plaster will need to be refinished to completely eliminate the discoloration. The pool warranty should be invoked to resolve this issue.

Since my pool is slightly over two years old, I contacted my pool builder requesting action. Will update the post when we have a plan.

 

[duraleigh]

Thanks for the update. That really helps us all "file it away" should something like that be reported on the forum again.

Your PB will hopefully be reasonable and help you with this one.

 

[Karmann]

Wow! Thanks for sharing with us.

Good luck getting it resolved with your pb

 

[bxcrwlly]

Re: Unidentified Dark Areas Under Tile Line - Update 12/12/1

Pool builder dispatched their finish expert. He arrived today 12/12/12. His initial diagnosis is "Hydration Discoloration." His plan is to perform a holistic pool acid treatment. Lights will be removed, waterfalls turned off with solar and heater bypassed. He said in 99% of the cases this process resolves the issue. It will take a week to perform this operation and plans are to start January 7, 2013. If his treatment works, it's on my dime. :santa: If not, no charge and next step will be to have the account rep for the plaster manufacturer on site to further diagnose the issue.
Happy Holidays to all!