Scaling Issue on Natural Flagstone

[mmanchester81]

This summer we've had several white stains develop on our flagstone raised waterfall as well as the flagstone spillover from the spa to the pool (see images below). I've been told these stains are calcium buildups but I wanted to confirm with you guys and see if everyone agrees. My CH has been within range (250-350) so I'm not sure why these stains have appeared this summer. Since the stains are on natural stone and are outside of the pool, I'm hesitant to put any chemicals on them and risk ruining it. Does anyone have any suggestions for getting rid of the scale as well as ideas on what caused them? Would adding scaletec or beautec as a sequestering agent in the future help prevent this from occurring? Appreciate any help!

 

[pooldv]

The isolated spots in the upper pic looks like efflorescence, which is minerals pushed through the stone by water from behind it. Eventually it will stop when there aren't any more minerals left or there is less water behind it. The lower pic is calcium scale. To reduce or eliminate the calcium scale maintain CSI between -0.3 and 0. More here, Pool School - Calcium Scaling. Muriatic acid will remove it. Start with 3 or 4 to 1 dilution with water and increase the strength if needed. Always add acid to water, never water to acid.

Those water features will push your pH up a lot increasing the likelihood of scaling. Running them less or only when people are outside will help if rapidly rising pH is an issue.

 

[mmanchester81]

Thanks for the advice. Is there a way to prevent the mineral from continuing to form on the flagstone? Are you saying the white deposits on the waterfall are not related to the pool chemistry?

 

[pooldv]

It seems possible that the upper pic, is that what you are calling a waterfall?, is efflorescence which is not related to water chemistry. It is possible that it is scale from the water that is channeling along the surface of the stone. It is hard to say for sure. The only way to prevent efflorescence is to prevent water from getting behind the stone. It is water from behind the stone that pushes the minerals through. That water can come from rain, sprinklers, slight leaks in the waterfall, etc.

 

[mmanchester81]

Do you have any recommendations on removing the efflorescence?

 

[pooldv]

Muriatic acid often works on it too. Scrape off the big chunks with a scraper or chisel first.

 

[JoyfulNoise]

Not to be contrary but I would NOT use MA on flagstone unless it is highly diluted. There is a product on the market by DryTreat called Eff-Erayza (Dry-Treat | HANAFINN Eff-Erayzaâ„¢) that can be used to clean stone. It is based on urea-hydrogen chloride (essentially a hydrochloric acid / urea adduct). The HCl lifts the calcium and the urea will mildly complex with calcium and other metal ions to hold it into solution. It will work to clean the stone without doing too much damage to the calcium carbonate matrix that holds the silica particles in place.

The best way to clean it is to find someone that does kierserite soda blasting as that will take away the calcium without damaging the stone....but that is a very specialized service not found in many places.

Just my 2 cent opinion....