gunnite pool with blue stains

[palmspriings]

Hello
I found this site as I was looking for an answer to my pool issue. I also have blue streaking, staining in my 3 year old gunite pool. From everything I have read, only copper causes blue staining. My water is professionally tested monthly and I have 2 years of records that show the water chemistry has been kept in balance. However, the hardness is very high as well as the conditioner. The water tests negative for copper and I do not have a heater. Several pool companies have been out to inspect but are also at a loss to explain the blue streaking/staining. The discoloration is on the walls as well as the floor of the pool. It is not sticky like algae, the pool water is crystal clear. However, if I scrape it hard with a screwdriver, it does come off, leaving white plaster behind it. It also seems to be accelerating in staining. A few other issues with the plaster.....I have a growing rebar stain, the surface is very rough and there is grey mottling everywhere. The 3 year old plaster looks like 10 year old plaster. It appears to be a major botch job from the plaster company, however I still cannot explain the blue staining. Help!!! Thanks for your time!

 

[zea3]

Hi, welcome to TFP! I would say you have at least 2 issues going on. The grey, rough surface is likely calcium scale. Scale comes from high calcium levels in the water. You may also have copper staining, even though it is not showing copper on the test. In order to help pinpoint the cause of your pool issues, we need a current complete set of test results. Even though you say your records show the water was in balance, that does not give us enough information to work with. Having the number values from the test results will tell us where to look first.

As for the blue stains, you may have used pool chemicals that contain copper without realizing it. If you can tell us the brand name and types of chemicals you use (chlorine, algecide, conditioner, ect) that will help us rule out copper as a source of the stain.

 

[JohnN]

What do you mean by "professionally tested?" If you mean a pool store, those are horribly inaccurate. It might be a good idea for you to get a good test kit, so you can know what is really going on with your water. Everyone here recommends the TF-100 (better value) but I have the K-2006. pool-school/pool_test_kit_comparison. Once a month testing is not enough to keep your water in good shape. This tells you how often to test your levels: pool-school/basic_pool_care_schedule

 

[palmspriings]

Thanks for the feedback.
John, I test the water several times a week. I am my own "pool guy" if you will. I mentioned the "professionally testing" only to back up my tests.

Mod Squad, I have looked into the calcium scaling, but the pics that I have seen show a whiter color than this gray-green on the plaster. In addition, there are many noticeable trowel marks where the discoloration is, leading me to a hydration problem. The roughness of the plaster isn't isolated to the discolored areas, none of it is smooth.

I was using 3" chlorine tablets that had 1.5% copper sulfate pentahydrate but stopped about 4 months ago. Here is the list of chemicals:
Pace dual purpose 3" chlorinating tablets. 93.5% Trichloro-S-Triazinetrione, 1.5% copper sulfate pentahydrate, 5% inert
Leslies Muriatic acid
Kem Tek liquid chlorine
Natural Chemistry phos free and pool perfect

The CYA was put in 3 years ago, I don't know which brand it was.

If we were to trace the blue blotching and streaking (there is almost a "ring" of it around the entire pool and isn't isolated to any one area) to the chlorine tablets, I would think this would be a common problem here in the desert and it wouldn't be such a mystery to the pool professionals in the area. Although I would be greatly relieved to find this simple fix to be the issue! Would this type of staining scrape off?

FAC 2ppm
TAC 2ppm
CH 500ppm+
CYA 150ppm
TA 80ppm
pH 7.6
Copper 0ppm
Iron 0ppm
Phosphates 100ppb

Another oddity is that my FAC and TAC are always the same....I have never needed to shock my pool.

Thanks so much for the help!

 

[duraleigh]

It's a very thin layer that gathers in some edges on the steps. It is in the spa and on the steps in the pool.

Pace dual purpose 3" chlorinating tablets. 93.5% Trichloro-S-Triazinetrione, 1.5% copper sulfate pentahydrate

It sure seems like zea3 and you are onto something. Your VERY high CYA indicates you have likely been using a lot of tabs that contain copper. Reports on the forum mostly indicate copper as a dark blue stain but I don't know of anything but copper that would stain like your pool has.

 

[palmspriings]

Thanks Dave, it's hard to tell as the VERY high CYA has been there from the start-up. I have typically used the liquid chlorine to balance and the tablets to maintain. The desert heat and sunshine sure does use up the chlorine fast!

 

[duraleigh]

So, it looks like you can remedy most of your issues but unsure you will be able to remove the copper stains.

I would suggest you start by not using ANY more pucks and , if you want to tackle the staining, you will need a kit to test accurately and often. Do it yourself and don't count on pool store advice.

 

[palmspriings]

Dave
Actually I am unsure of the cause of the blue staining. I am not ready to say that it is from the tiny amount in the chlorine tablets. I haven't used the tablets for 4 months, yet the staining continues to accelerate. My thoughts are that if it were from the tablets, the staining would have stopped and it would be a common problem in the desert. However, I'm hoping the tablets are the answer

 

[zea3]

The copper from the tablets would still be in the water, it doesn't evaporate out. You can test the stain with a Jack's Magic stain kit. The stain kit helps to identify the source of the stain. You can also put some dry acid in a sock, dip the sock in the pool and hold it against one of the stains (wear gloves for this test). If it lightens or removes the stain it is likely copper and the pool will need an acid wash to remove it.