Rough and Discolored Pool Plaster - Why and how to fix?

Palpatine

Bronze Supporter
Sep 3, 2019
250
West Hills, CA
Unsure. Did you have high CH and/or high pH in the past that might have created the scale? Scale can form with dirt or other organics in it and look like a stain. But the puck should have lightened it as it is acidic and would cut through the scale.
I had surgery back in November and neglected the pool for a couple of months. Definitely had super high pH for a while (was purple a few times) and had terrible wind storms with a ton of debris that sat in the pool for weeks. By the time I cleaned it up that's when I noticed the stains under the debris.

Original theory was that it was organic... maybe some kind of sap or something, but shouldn't the slam have taken care of that?
 

mknauss

Mod Squad
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May 3, 2014
42,042
Laughlin, NV
Pool Size
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Chlorine
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If leaves sat on the bottom of the pool, the tannins wills stain and will take a long time for it to lighten. I would suggest just maintaining your FC in the upper target range and brush when you can.
 

Palpatine

Bronze Supporter
Sep 3, 2019
250
West Hills, CA
If leaves sat on the bottom of the pool, the tannins wills stain and will take a long time for it to lighten. I would suggest just maintaining your FC in the upper target range and brush when you can.
Okay, got it... so I should keep my pH in normal range then?

I've been brushing with a metal brush but doesn't seem to help much. I'll keep the FC up and brush regularly.

Btw, what is "a long time"... we talking months, years? Should I hit it with some sand paper?
 

mknauss

Mod Squad
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May 3, 2014
42,042
Laughlin, NV
Pool Size
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Pentair Intellichlor IC-40
pH in the 7's.

It can take several weeks to over a month. Is the area rough compared to the rest of the pool surface?
 

Palpatine

Bronze Supporter
Sep 3, 2019
250
West Hills, CA
Well, it's been months now so I figured I'd update this thread in the hopes that someone can come up with a miracle for me.

Stains are still there. I've been on top of the my chems:

FC 4-8 (I lose a fair amount every day in this heat and my pool gets full sun every day)
CC 0
PH 7.5 to 7.9 (still rises pretty quickly but I'm on top of it and keeping it in range with MA)
TA 50
CH 625
CYA 50 (just put a couple of pounds in yesterday to get it here... was 30-40 a few days ago)

Doesn't seem to be calcification, or organic as I've slammed and kept my fc pretty high. Metals test show no issue (iron .1 and copper .2).

To save everyone from reading the whole thread, these stains seemed to develop during the winter with high winds and a ton of debris sitting on the bottom of my pool for weeks. Pool was neglected for a couple months (no chlorine, high PH) after I had surgery and I never expected the debris would leave a stain or I would have just hired someone to clean it while I was out of commission. Oh well, lesson learned.

Anyone have any idea how to get rid of it... or have an unorthodox method they think is worth trying? The plaster is only a year old and I'm just figuring I'll have to drain and acid wash at this point.

Thanks
 

Bperry

Gold Supporter
Aug 20, 2020
606
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
Well, it's been months now so I figured I'd update this thread in the hopes that someone can come up with a miracle for me.

Stains are still there. I've been on top of the my chems:

FC 4-8 (I lose a fair amount every day in this heat and my pool gets full sun every day)
CC 0
PH 7.5 to 7.9 (still rises pretty quickly but I'm on top of it and keeping it in range with MA)
TA 50
CH 625
CYA 50 (just put a couple of pounds in yesterday to get it here... was 30-40 a few days ago)

Doesn't seem to be calcification, or organic as I've slammed and kept my fc pretty high. Metals test show no issue (iron .1 and copper .2).

To save everyone from reading the whole thread, these stains seemed to develop during the winter with high winds and a ton of debris sitting on the bottom of my pool for weeks. Pool was neglected for a couple months (no chlorine, high PH) after I had surgery and I never expected the debris would leave a stain or I would have just hired someone to clean it while I was out of commission. Oh well, lesson learned.

Anyone have any idea how to get rid of it... or have an unorthodox method they think is worth trying? The plaster is only a year old and I'm just figuring I'll have to drain and acid wash at this point.

Thanks
I’ve got a light stain from a decomposing bullfrog that got under the cover during winter. Would be interested in hearing ideas as well.
Lots of what I hear about acid washing says it can help but also take a layer off the plaster reducing its lifespan. Is waiting a few years to see if it fades a tolerable plan?
 

zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
13,922
Houston, Texas
Your CH is much higher than reported previously, so either some CH has lifted and gone back into solution, you have used cal-hypo in the pool, you have high CH fill water, or you have a testing error. In order for scale to dissolve back into solution you must consistantly keep the pH at 7.0-7.2 and no higher. As pH rises the water stops pulling CH from the pool surface and when pH reaches 7.8 or higher with high calcium levels it will start to deposit scale on pool surfaces.
 

Palpatine

Bronze Supporter
Sep 3, 2019
250
West Hills, CA
Your CH is much higher than reported previously, so either some CH has lifted and gone back into solution, you have used cal-hypo in the pool, you have high CH fill water, or you have a testing error. In order for scale to dissolve back into solution you must consistantly keep the pH at 7.0-7.2 and no higher. As pH rises the water stops pulling CH from the pool surface and when pH reaches 7.8 or higher with high calcium levels it will start to deposit scale on pool surfaces.
Hi @zea3 ,

I tested the CH this time using the method where you anticipate high CH (drops of 25 to save on reagent) and it is definitely higher than last time. My last 2 times at Leslie's the numbers were 458 and 547... I had them test for metals but I definitely don't rely on their results for anything else. Just an fyi... and seemed close enough to my numbers.

My fill water is CH 90 and @mknauss had mentioned that I'm not likely scaling a few posts back so I let my PH rise to normal range.

While I thought the stain was spreading awhile ago, it does seem like it has remained localized to half my deep end. Kinda hard for me not to connect the dots of having a bunch of debris on the floor for a while... letting the fc go to 0 and ph go high in the winter... then developing the stain. I'm certainly not saying your wrong @zea3 and I truly appreciate your assistance... but the lower pH didn't seem to help when I lowered it for a couple of weeks.

Also was mentioned that the stain could be tannins from the debris. I feel like that makes the most sense but scrubbing it does pretty much nothing at this point. I got some 80 grit wet/dry sandpaper and was considering hitting it lightly with that. Good or bad idea?

I'd take fresh pic but the sun is out in full force right now and it's really hard to see the stain in the sun. It's when there's a shadow on it that it's really easy to see. I'll get fresh pics tonight when the sun goes down.
 

zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
13,922
Houston, Texas
You have to be patient and keep the pH at 7.0 consistently for more than a couple of weeks to see if this helps your situation. Your TA is also kind of low for pH to be getting up to 7.9 You don't want the TA to crash as it will give you problems controlling your pH. Use baking soda and try and keep the TA in the 70-90 range.

Do you use fountains, waterfalls, bubblers, or have the returns pointed so they churn the surface of the water?
 

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Palpatine

Bronze Supporter
Sep 3, 2019
250
West Hills, CA
You have to be patient and keep the pH at 7.0 consistently for more than a couple of weeks to see if this helps your situation. Your TA is also kind of low for pH to be getting up to 7.9 You don't want the TA to crash as it will give you problems controlling your pH. Use baking soda and try and keep the TA in the 70-90 range.

Do you use fountains, waterfalls, bubblers, or have the returns pointed so they churn the surface of the water?
I don't have any water features, except for bubbles in the spa which we rarely use, and returns don't churn the surface very much. pH has risen up consistently ever since re-plastering about a year and a half ago... I control it with MA. Even if I take it down to 7.3 or 7.4, it's up to 7.8 or 7.9 or greater within a couple of days, whether we swim in it or not.

I was told not to worry about the TA as long as my CSI is in range, which it is, but I'll bring it up next week. That won't effect my pH?

So it sounds like you're still convinced it's scale even though it hasn't spread to other parts of the pool. I'll give it another go with the low pH after I adjust the TA. Is that the correct order?

Patience has never been my strong suit... also, I don't have a heater bypass so keeping pH at 7.0 definitely makes me a bit nervous. Do you think 7.2 will be sufficient?

Thanks @zea3
 

Rancho Cost-a-Lotta

Silver Supporter
Apr 10, 2018
2,292
Rancho Cucamonga, CA
Pool Size
18735
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45
Are you able to set suction from pool and set return to spa? If you have the setup, you should be able to overflow the spa into the pool. The combination of the bubbles and the overflow should create significant aeration.
 

Palpatine

Bronze Supporter
Sep 3, 2019
250
West Hills, CA
Are you able to set suction from pool and set return to spa? If you have the setup, you should be able to overflow the spa into the pool. The combination of the bubbles and the overflow should create significant aeration.
Yes, that's the standard flow for my pool. However, the spa overflow is pretty much the same height as the pool water level... not the best design imo, but it is what it is. Maybe that is the cause of the rapid pH increase though.
 

Rancho Cost-a-Lotta

Silver Supporter
Apr 10, 2018
2,292
Rancho Cucamonga, CA
Pool Size
18735
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45
My apologies, I misread the post above believing you were trying to raise TA through aeration..

Correct, the overflow from the spa to the pool will cause pH rise.
 

onBalance

TFP Expert
LifeTime Supporter
In The Industry
Jul 25, 2011
1,166
Utah
While calcium scaling may be the discoloration problem, consider the below info as another possibility.
If it is only gray mottling discoloration, then a low pH treatment isn't going to make much difference.
 

Palpatine

Bronze Supporter
Sep 3, 2019
250
West Hills, CA
While calcium scaling may be the discoloration problem, consider the below info as another possibility.
If it is only gray mottling discoloration, then a low pH treatment isn't going to make much difference.
Thanks for the info @onBalance

I think I do have some of that gray mottling but I think this stain is different... of course I could be wrong, but this does appear a bit more brownish than gray. Hard to tell though.

Is there anything to do to fix the hard trowling marks? Or am I just outta luck?

Again, cause I know it's a pain to read through this entire thread, but it seems very suspect to me that these stains were directly under a bunch of debris that sat there for a a couple of weeks, at least, until I cleared it out. Just odd that the pucks didn't really do anything even when rubbing directly on the stain.
 

Palpatine

Bronze Supporter
Sep 3, 2019
250
West Hills, CA
Btw, @onBalance , I just finished reading the entire thread (didn't realize how short it is) and while I do have some of those mottling/ hard trowling marks, this stain occurred well after a year of the new plaster.

Edit: Or maybe just over a year... lockdown has all my timeframes messed up.
 

onBalance

TFP Expert
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Jul 25, 2011
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Utah
If it is actually gray mottling, or something else, the best remedy is often to drain and sand and polish the surface. High speed sanders are used and should remove the discoloration and expose a new polished and smooth finish.
 
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Palpatine

Bronze Supporter
Sep 3, 2019
250
West Hills, CA
Here's a couple of pics from yesterday evening. Please excuse the clumps of hair on the bottom... my pool is usually cleaner but we had a full day of swimming yesterday. Pool Stain 1 pic.jpgPool Stain 2 pic.jpg
 

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