Stained Waterline Grout

SDPoolOwner

Active member
Mar 20, 2022
28
San Diego
All -

I renovated my backyard last fall, including resurfacing my pool and installing new glass waterline tile. I regularly maintain water chemistry and all was good until.....the water warmed and the kids increased pool usage. Just a few days ago I noticed that my grout was discolored between ~75% of my tile. No issues in the spa or spillway and very little on the end of the pool where the spa flows into the pool. The main issue is on the deep end where there is less water movement. I am looking for help with the following:

1. Is it algae or a stain caused by plants next to the pool?
2. What is the best way to clean?

In regards to #1, does it look like algae or could it be a stain from plants? With the backyard remodel we put in Maiden Grass above our pool wall and over the past few months it bloomed and we get a a material amount of debris on the pool surface. I remove nearly daily with a fine mesh net, but it sits on the surface a good amount of time. The net also is stained. BTW, our pool weir door does not operate well (another thing to fix) so the surface is not skimmed well. Also, on Sunday night, I added a gallon of liquid chlorine to my 12,000 gallon pool. Yesterday (Tuesday) FC and TC, using TPK was ~4 and the same color to the eye, so I assume CC was ~0. Just tested again and FC and TC seem to be 2.5. pH = 7.7, water temp 83 deg F so about to add some acid now and then more chlorine this evening.

2. At first, I thought it could be algae so I tried rubbing it with a chlorine puck. It seemed to lighten it that day, but a day later, it seemed to be back. I just tried using a 25% bleach / 75% water solution and it seems better, but only time will tell.

Thank you for your help.
 

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Last edited:
All -

I renovated my backyard last fall, including resurfacing my pool and installing new glass waterline tile. I regularly maintain water chemistry and all was good until.....the water warmed and the kids increased pool usage. Just a few days ago I noticed that my grout was discolored between ~75% of my tile. No issues in the spa or spillway and very little on the end of the pool where the spa flows into the pool. The main issue is on the deep end where there is less water movement. I am looking for help with the following:

1. Is it algae or a stain caused by plants next to the pool?
2. What is the best way to clean?

In regards to #1, does it look like algae or could it be a stain from plants? With the backyard remodel we put in Maiden Grass above our pool wall and over the past few months it bloomed and we get a a material amount of debris on the pool surface. I remove nearly daily with a fine mesh net, but it sits on the surface a good amount of time. The net also is stained. BTW, our pool weir door does not operate well (another thing to fix) so the surface is not skimmed well. Also, on Sunday night, I added a gallon of liquid chlorine to my 12,000 gallon pool. Yesterday (Tuesday) FC and TC, using TPK was ~4 and the same color to the eye, so I assume CC was ~0. Just tested again and FC and TC seem to be 2.5, so plan to add more chlorine today.

2. At first, I thought it could be algae so I tried rubbing it with a chlorine puck. It seemed to lighten it that day, but a day later, it seemed to be back. I just tried using a 25% bleach / 75% water solution and it seems better, but only time will tell.

Thank you for your help.
Here is a photo shortly after using the bleach solution. Again better, but not 100% clean and hard to say if it will stay that way.
 

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