Spa-ool plaster has changed from beige color to blue color

[AussieLady]

I have an 18 month old 1200 gallon in-ground bromine spa-ool. I maintain the spa-ool using the BBB method. We went overseas on vacation for 3 weeks and I asked a friend who has had his own pool(s) for many years to visit each week and just add 4 cups of chlorine bleach and about 8 oz. of muriatic to maintain the bromine level and pH/alkalinity. The reason for the muriatic is that I have a waterfall and the pH usually rises over a 7 day period.

When we returned from our trip, judging by the amount of chlorine bleach and muriatic I had left our friend, he had not added anything to the spa-ool. He does not test his own pool but relies on the clarity of the water as his guide. I now think perhaps he applied that same logic (or lack thereof) to my spa-ool which is why he did not add any bleach or muriatic in our absence. When I tested the water, the pH was way down at 6.8 (maybe lower) and the alkalinity was around 30! I adjusted the water balance back to a pH of 7.6 and alkalinity to around 90. Bromine/chlorine was also low - although the floating brominator helped - so I also shocked the spa-ool to raise the bromine/chlorine level.

The reason I am posting is that the spa-ool has a Pebble Tec finish and the plaster in which the tiny pebbles are embedded was beige (color known as Sandy Beach). After returning from vacation the plaster in which the pebbles are embedded has changed color to a turquoise blue. We have scrubbed the walls and floor with a hard brush, and while some debris seems to come off, the plaster itself still remains blue.

Can anyone suggest why the beige plaster turned blue? And is there any way to restore it to beige?

Thanks!

 

[JamesW]

Re: Spa-ool plaster has changed from beige color to blue col

I think that it is most likely copper from the heat exchanger of the Laars LX250 Heater caused by low pH.

8 ounces of acid is too much to add to 1200 gallons at one time. 32 ounces of Clorox is also too much to add at one time. Chemicals should be adjusted only after testing and calculating the correct amount. It is not a good idea to just add them at regular intervals without checking.

 

[AussieLady]

Re: Spa-ool plaster has changed from beige color to blue col

Thanks for the response, James. Actually, I always test my water before adding anything, but as I have been testing at least twice a week for 18 months, I've sort of got to know my water (so to speak) and can pretty much assume (although I always confirm with testing) that the pH has gone high after about 7 days. I guess that's why I felt confident in asking my friend to add 8 oz. of muriatic once a week. But as I said in my post, he didn't.

All of that said, the heater was not on at all while we were away on vacation. The spa-ool is an outdoor in-ground spa-ool (photo attached) and 1200 gallons is too much to keep hot all the time. We only turn on the heater about 2 hours in advance of getting in to the spa-ool, and then we turn it off a few hours after bathing.

Any and all input is always very much appreciated. This pool ownership is an ongoing learning experience!

 

[JamesW]

Re: Spa-ool plaster has changed from beige color to blue col

The heater does not need to be on to be damaged by low pH. If he didn't add acid, then I'm not sure why the pH and TA would be so low. If the pH looks about 6.8 or lower, then it might be much lower.

What were the pH and TA before you left? "Turquoise blue" is a classic copper compound color. The bromine tabs could account for the pH drop, as they are acidic. How many tabs were used during the time you were gone? Were they added through the skimmer?

Can you post a current picture?

 

[AussieLady]

Re: Spa-ool plaster has changed from beige color to blue col

My pH was normal at around 7.5 and alkalinity was normal around 80 before I left. I agree with what you are saying about it odd that the pH and TA were very low if he didn't add muriatic. My test kit only reads as low as 6.8 for the pH and yes, it could have been a lot lower. But my test for alkalinity (two drops of purple reagent, then count the drops of #3) gave me a reading of around 30, so I know the pH had to be pretty low as the two remain somewhat in line with each other. I had 4 one inch bromine tabs in the floater and 2 of those (albeit smaller) were still remaining after the 3 week absence.

Attached are photos from today showing the blue coloring in the plaster. Note that it is only the plaster in the water that has changed to blue. Above the waterline remains beige. Obviously this is a huge clue, the question is, what on earth am I doing wrong that could cause plaster to change color so drastically?

Thanks again for helping me try to identify the problem and resolve this mystery!

 

[AussieLady]

Re: Spa-ool plaster has changed from beige color to blue col

Sorry, I should have also added that the blue color will not scrub off with a hard brush. <sigh> And in reality, I suppose I should be grateful that it is blue -- which is at least pool water color -- and not some ghastly red, or purple, or non-pool water color! :?

I'm also attaching a pic from some months ago which I took of a rust stain (and thankfully now I know what causes it and how to fix it so that is no longer an issue), but you will see the color of the plaster under water back then was beige just like the color of the plaster above the water now.

 

[JamesW]

Re: Spa-ool plaster has changed from beige color to blue col

The color is most likely from copper from the heat exchanger. I think that an acid wash is probably the only thing that will clean the stains off.

I don't think that this is something you did wrong. This did not happen while you were taking care of the pool. Whatever the other person added is most likely responsible.

Two 1-inch bromine tabs would not lower the pH and TA that much. He had to add something. Have you asked him what he added?

 

[AussieLady]

Re: Spa-ool plaster has changed from beige color to blue col

I haven't asked him what (if anything) he added, but I will. I have Googled plaster color change repeatedly and am coming up with nothing. What on earth could change the color of the plaster that drastically? Do you still think it's the heater?

Are there any products on the market that people use to deliberately "blue" their plaster?

 

[JamesW]

Re: Spa-ool plaster has changed from beige color to blue col

I think that it's probably copper. He might have added copper algaecide, but the low pH could have caused copper from the heater to be corroded.

 

[AussieLady]

Re: Spa-ool plaster has changed from beige color to blue col

I asked my friend if he had added anything other than muriatic and bleach to my spa-ool during my absence and he assured me "no".

From what you have said, what I have been able to research via Google, and the fact that the pH was extremely low upon my return from vacation, definitely points toward copper staining the plaster a blue color.

So that said, my (hopefully but can't make any promises) last question is ...... do I need to do anything about the copper at this point? My pH and alkalinity are back in the normal range (tested) and my chlorine level is high normal. Will the plaster keep going a deeper blue? Or is what I've got pretty much all it's going to do?

Thanks again!

 

[JamesW]

Re: Spa-ool plaster has changed from beige color to blue col

Most likely, he added about 16 ounces of acid to account for the TA drop of 50 ppm. As far as the copper is concerned, the biggest risk is turning people's hair blue when they go under water.

You could have the water tested for copper to see what is left in the water, but there might not be any left in the water if it has all precipitated as stains. Some of the copper could go back into solution over time, but the stains are most likely permanent until they are removed by an acid wash.

You could try a little bit of dry acid in a cloth on a spot to see what happens. You could also try some ascorbic acid (Vitamin C) on a spot to see what happens.

I think that the best thing to do is probably going to be to drain, light acid wash and refill. Due to the corrosion in the heater, you will probably get some more copper over time as the heat exchanger deteriorates.

 

[JamesW]

Re: Spa-ool plaster has changed from beige color to blue col

I think that what might have happened is that your friend missed a week and added 16 ounces of acid and 64 ounces of bleach at one time. This would have lowered the pH very low and it would have raised the bromine level to about 60 ppm. Due to the low pH, much of the bromine would be in the form of elemental liquid bromine. The high concentration of elemental bromine (Br₂) and low pH would create a very corrosive environment.