Scaling

[floridarandy]

Our 20 year old marcite pool was resurfaced in PebblesStone 5 years ago. We've just started getting a couple of calcium "bumps" and scaling. The outfit that did the pebblestone reports this is "normal" as these surfaces can cure for 5-7 years. They recommend acid washing with the following instructions. Please comment before we begin. Thanks.

In Pool Acid Wash
Adding Muriatic Acid to water lets the aggressive water work on surface
24/7.
Removing light and floor heads is recommended. Also by-pass older
heaters without Titanium coils.
To start, make sure chlorine level is down to 1.0 or less. Add muriatic
acid to the rate of 1 gallon per 3,000 gallons water to start. Then
maintaining alkalinity level at 20 ppm or lower. Using a sequestrian
product will help in lifting scale and metals from surface.
Leave pump running 24/7. Start brushing surface and cleaning filter
daily.
Make sure to keep alkalinity at 0-20 ppm or below.
This is a 7-14 day process as needed. When satisfied, rebalance
chemicals. You might need to dump a few feet of water and refill with
fresh water. Check hardness for this. Over 600 ppm, usually needs
dilution (fresh water).​

 

[JamesW]

Do you have any pictures?

What are the chemistry readings?

What is the CSI?

The bumps sound like they could be calcium nodules.

 

[ajw22]

Please post a complete set of water tests from your own test kit. There are other less agressive ways of trying to rid a pool of scale first. Let's start with where your water chemistry is right now...

FC
CC
pH
TA
CH
CYA
CSI
Water temperature

I suggest you read ABCs of Pool Water Chemistry and Calcium Saturation Index (CSI) - Trouble Free Pool which is key to controlling and removing scale.

 

[floridarandy]

Last Chemistry - Jan 11

FC 3.0
CC 0.0
PH 7.8
TA 70
CH 450
CYA 40
BOR 0
TEMP 65
CSI .10

Pictures attached

 

[floridarandy]

Been looking for a 50lb quantity. Is this the right stuff?

Is This The Right Stuff?

 

[ajw22]

Borates in pool - Further Reading

www.troublefreepool.com

Easiest way is to use Boric Acid from

boric acid | Duda Diesel Alternative Energy, Chemicals & Industrial Supply Store

 

[floridarandy]

thanks. see scaling thread to continue my questions regarding borates and scaling.

 

[floridarandy]

Today's chemistry 1-15

FC 6.0
CC 1.0
pH 7.2
TA 60
CH 350
CYA 35
BOR 8
TEMP 74F
CSI -.57

So, with the beginnings of scaling and two small calcium nodules what should my approach be? Borates are also low so can I bring them up with Boric Acid while I attempt to deal with scaling? This would raise pH obviously.

I look forward to recommendation. Thanks.

 

[ajw22]

I don't think what you have is scale. Scale does not occur in isolated areas.

Calcium nodules and scaling are two different problems. @onBalance explains calcium nodules here...

Calcium Nodules in pools

What are calcium nodules? In swimming pools and spas, they are small mounds, bumps, deposits, or “slag” piles of calcium carbonate which are formed from material that has been released from the plaster. The small calcium nodules are rough to the touch, hard, and generally gritty. Nodules may...

www.troublefreepool.com

As he says calcium nodules primarily form due to bonding failure (delamination) of a new coat of plaster, and occasionally from severe craze cracking, and that they were responsible for this plaster defect. Plasterers learned that bonding failure rarely occurs on fresh gunite substrates (new pools); however, bonding new plaster (replaster) to old plaster surfaces can occasionally be difficult to achieve. This is why most calcium nodules occur in replaster jobs.

Are those areas you identified as scaling rough to the touch like sandpaper?

Run your water chemistry on the low end of CSI between -0.3 and -0.6 for a few months and see if the aggressive water dissolves some of whatever it is. You always want to run your pool water CSI negative to prevent scaling.