Stubborn stains and discoloration in new quartz plaster pool

[EddieDPT27]

Hello all decided to finally join after being along time lurker before deciding to build new pool.

My pool was plastered in Sep 2021 with quartz plaster. Everything began as expected and start up was performed by builder via traditional bicarb start up. Everything looked amazing and perfectly even the first 4 weeks of pool. Builder kept tabs of pool the first month. Only small hiccup was hose end touched plaster during initial fill and left small orange stain which easily brushed off. Pool was brushed consistently every day. Good amount of plaster dust was present but disappeared quickly. Pool pump was run continuously. At the 30 day mark salt was added and SWG was turned on. Later that day I noticed two small dark spots form in deep end close to main drain. I brought it up to builder and he said might be from salt and they would treat it. Unfortunately stain has continued to spread across deep end an continues to spread. The builder has attempted various treatments. Jacks magic number 2 and 1 with little effect or change. Then it was decided we should do an acid bath/zero alkalinity treatment. This was performed and it decreased/lightened the stains significantly. Unfortunately the stains have returned. At this point not sure if this is metals, mottling from improper plaster practices, or calcium scale with metals trapped underneath. I have spoken to a few people that insist this is metals/minerals based staining. There is talk of another stain treatment, acid wash, or replaster. Any help is greatly appreciated.

Today’s water parameters

FC 5
TA 80
CYA 40
PH 7.4
CH 450

CH of fill water 150

Last picture is initial stain and others are current condition of stains.

 

[ajw22]

Welcome to TFP.

Looks like typical mottling to me.

Another acid wash will not accomplish anything and just etch the plaster further.

Have you tried sanding an area with 80/100 grit wet/dry sandpaper?

@onBalance

 

[EddieDPT27]

Welcome to TFP.

Looks like typical mottling to me.

Another acid wash will not accomplish anything and just etch the plaster further.

Have you tried sanding an area with 80/100 grit wet/dry sandpaper?

@onBalance

No I have not attempted sanding an area. Seems like a good suggestion.I don’t think this can be considered typical mottling as I have never seen this much in a concentrated area. The rest of the pool looks great although stains appear to be spreading.

 

[ajw22]

Stains from metals in the water would not be concentrated in an area.

Have you had your water tested for iron and copper at a pool store?

I think those mottled areas are due to the plaster mix and troweling in that area.

 

[EddieDPT27]

Stains from metals in the water would not be concentrated in an area.

Have you had your water tested for iron and copper at a pool store?

I think those mottled areas are due to the plaster mix and troweling in that area.

I actually tested recently with iron/copper testing negative. Although in theory once metals come out of solution and plate out you could technically get a negative test. The confusing part of this is it began immediately after adding salt. What is most worrisome is that it continues to spread progressively.

 

[ajw22]

What brand salt was used?

You say “stains” are still forming. If that was from metals in the water it would show in tests as you would still have metal in solution.

 

[EddieDPT27]

What brand salt was used?

You say “stains” are still forming. If that was from metals in the water it would show in tests as you would still have metal in solution.

Aquasalt is the brand. It appears that new grey discoloration/mottling areas are appearing slowly moving towards the shallow end of pool.

 

[ajw22]

The Art of Good Pool Plaster Color

An attractive plaster color (other than white) is often preferred by pool owners. However, it is very difficult for plasterers to produce a uniform and consistent color. The reality is that there will always be some minor shading (mottling) and variation in the color and can never be uniform...

www.troublefreepool.com

Being Blamed for Plaster Discolorations? Don't Get Hoodwinked

Some newly plastered pools (including quartz and pebble finishes) may develop either color fading, white soft spotting (also incorrectly called "spot etching" by some plasterers), white streaking (in colored plaster), calcium nodules, gray mottling discoloration (of white plaster), spalling...

www.troublefreepool.com

Plaster Installation and Maintenance - Further Reading

www.troublefreepool.com

 

[onBalance]

Using some 80 grit wet&dry sandpaper, try sanding a small area (hand size) where the color is darker or discolored. Then sand another area where the color is lighter or no discoloration. Let us know what effect that has.

 

[EddieDPT27]

Using some 80 grit wet&dry sandpaper, try sanding a small area (hand size) where the color is darker or discolored. Then sand another area where the color is lighter or no discoloration. Let us know what effect that has.

Ok will do. Thank you.

 

[EddieDPT27]

Using some 80 grit wet&dry sandpaper, try sanding a small area (hand size) where the color is darker or discolored. Then sand another area where the color is lighter or no discoloration. Let us know what effect that has.

I tried this although it was difficult. It seemed that the area where color is lighter got slightly darker. No big changes in darker areas.

 

[onBalance]

With that result, it sounds like gray mottling discoloration. But not sure.
Was there a color pigment added to the quartz finish?

Read these two posts.

How White Pool Plaster Turns Blotchy

This experiment below explains how white pool plaster can become blotchy gray, and also have white areas mixed into the gray areas. Both white pool plaster coupons below have been in water for one year. Sometimes the water was slightly aggressive (negative CSI), and sometimes the water was...

www.troublefreepool.com

How White Pool Plaster Can Turn Gray

One would think that when mixing white cement with white limestone aggregate, the final pool plaster product would always be white. But that is not always the case. Unfortunately, white pool plaster sometimes turns gray (or grey) either immediately or a few months after the pool is filled with...

www.troublefreepool.com

 

[EddieDPT27]

When they performed the zero alkalinity/acid bath the discoloration improved significantly but returned shortly after. If Grey mottling is the situation I assume replaster is the only solution? Also what is the difference between hydration stains and grey mottling? Also the discoloration continues to spread progressively towards shallow end. There was no color pigment added to mix.

 

[onBalance]

So if there was no color pigment added, then it is probably white cement along with the color quartz as the plaster mix. That would make it more likely to be gray mottling discoloration as discussed in those two posts.

It is not likely that acid washing will remedy the mottling discoloration, and will instead, make the surface etched and rough to the touch. That would significantly reduce the life of the finish.

Plasterers should not use the term "hydration" to describe severe mottling because all cement goes through a normal hydration hardening process when water is added. In other words, "hydration" is normal and always happens when water is added to cement. But when too much calcium chloride is added to the mix, and late hard troweling is performed, then that causes an abnormal or severe hydration situation and results in a darker shade or color as it discussed in those two posts.

Perhaps a good sanding and polishing would work as a more appropriate remedy. If not, then replastering may be needed.

 

[EddieDPT27]

So if there was no color pigment added, then it is probably white cement along with the color quartz as the plaster mix. That would make it more likely to be gray mottling discoloration as discussed in those two posts.

It is not likely that acid washing will remedy the mottling discoloration, and will instead, make the surface etched and rough to the touch. That would significantly reduce the life of the finish.

Plasterers should not use the term "hydration" to describe severe mottling because all cement goes through a normal hydration hardening process when water is added. In other words, "hydration" is normal and always happens when water is added to cement. But when too much calcium chloride is added to the mix, and late hard troweling is performed, then that causes an abnormal or severe hydration situation and results in a darker shade or color as it discussed in those two posts.

Perhaps a good sanding and polishing would work as a more appropriate remedy. If not, then replastering may be needed.

Not sure if this helps but I have noticed the areas that are discolored are much rougher than the unblemished areas.

 

[Newdude]

Dang Eddie, ya got me. I just spent a good 10 minutes trying to figure out the AMAZING faux sand / beach entry in the first pic. But its just your finger. *sigh*

 

[onBalance]

"Not sure if this helps but I have noticed the areas that are discolored are much rougher than the unblemished areas."

I am not sure why the plaster would be rougher and would indicate.