what is this white stuff?

[patplh]

we've been the owners of this pool for almost 2 years and each year, we open with this hard white residue along certain parts of the rock wall. It drips down to the pool tile and we have to scrape it off. We thought after the first time, we wouldn't have to do it again, but it comes back after a few months. Our guess is that the previous owners were trying to fill some cracks and used the wrong product.. but I'm worried it's something worse since it keeps coming back. I was wondering if it's plaster, but it originates pretty high up above the pool water, so i'm guessing not? is it calcium buildup? when I had the pool professionally closed one year, I asked the guys about it and they said to get some muratic acid, which we haven't done yet. just thought i'd try to get some opinions from the experienced folks out there.
thanks

 

[JasonLion]

That looks like efflorescence, a process where minerals in the stone or in the grout are brought to the surface by water leaking through the wall. The only way to completely stop it is to stop water from coming through the wall.

 

[patplh]

Thanks Jason - is this a sign of damage? should we be concerned that in the long term this will cause major issues or is it just a cosmetic thing?
thanks again

 

[PoolGuyNJ]

Eventually, but this is many years, it will weaken the cement. It is, as Jason said, effervescence, a process where the calcium in the cement or mortar is brought to the surface by the weeping water. Cements have a lot of calcium in them.

To stop it from recurring, you will need a drainage system put in to capture the run off water from the hill and carry it away from the wall. The back of the wall should have been sealed, not unlike the foundation of a basement.

The remove what is showing now, you will need a bucket (non-metallic!), an acid resistant scrub brush (shower brushes work well), rubber gloves, goggles, a hose, and diluted muriatic acid (3 parts water and 1 part acid), some baking soda and likely some washing soda too.

Scrub the white stuff with the brush and acid water mix. Rinse well. Repeat as needed. When its removed, rinse/scrub the area with a water and baking soda mix to neutralize. Expect fizzing.

Pour the rest in the pool and add baking soda and washing soda as needed to rebalance the pool water.

Scott

 

[257WbyMag]

I have to contend with that every year. It's only by the waterfall but still, it takes a while to get off of there.