These photos show the side of the pool at the top 6" or 8" or so below the bottom edge of the tile line. You can see in the 2nd photo that the surface is not only stained, but fairly rough. I have tried an acid wash and also scrubbing with other heavy duty cleaners, but with no affect whatsoever.

I should also note that since the pool has been filled and maintained (after these photos were taken, the stain looks much more greenish than in the photos, which look more brown/grayish. It may just be that the water gives it the greener tone, just like the unstained parts of the pool look blue once water is added, but white when it is empty...

I was hoping that it would fade after the pool was maintained for a while with chlorine, but it has not changed at all. As you can see, there are small pieces of plaster that have chipped off, and those are the color the plaster should be, so I am thinking of trying a very heavy/hard wire brush on the surface to remove it, but that could be pretty hard on the plaster. I did try a brass brush, which is much less aggressive, but that did nothing.

I am hesitant to try use a stain remover since I have been trying to avoid introducing new chemicals to my pool that would throw off my balance, but I'm not sure how else to get rid of this stain. I know the pool is clean and balanced, but it is a little embarrassing when we have guests over to use the pool.

Thanks for your input!

How strong was the acid you used, I assume you used diluted Muriatic.

That really looks like calcium deposits.

Scott

I agree with Scott. If you look carefully you can see the dingy gray continue uninterrupted from the tile to the plaster below. Any stain (organic or otherwise) that's embedded in scale is going to be very difficult to remove.

I would have to check the bottle to be sure, but I believe the acid is only about 16%.
You're right about the deposits on the tile, but I want to say that that is not there anymore...or maybe I just don't notice it since the tile is mostly under the water and is less noticeable since it is much darker than the plaster.

Should I try a stronger percentage acid? Would I just need to test my pH/TA after doing the wash and add chems accordingly due to all the extra acid that I will have added to the pool (assuming that I do only a partial drain and spray/wash the stained area)?

What do you think about the hard wire bush idea? Might that do too much damage to the plaster surface?

Thanks for the input so far!

That is scale, and it is not going to come off with any of the things you are considering. Too strong of acid will eat your grout, and the wire brush will just scratch. The tile can be cleaned with a bead blaster and glass media, but the plaster is shot.

Do you know what your calcium levels are? That looks like a pool that was not drained for a very long time and the calcium levels allowed to build. It is a poster pool for maintaining CH levels properly.

How far south in Southern California are you?

Not to glom on, but that clearly looks like scale. If it has taken a greenish tint, that's from algae imbedding itself onto the scale. simicrintz is the go to guy for scale.....follow his advice.

I'm near the 605 fwy, Long Beach area.
The pool was in really bad shape when I bought the house. It was nearly empty and extremely thick, green water. Water had not been on the stained portion of the pool for quite some time since the house was vacant for many months before I got a hold of it.

I may be able to recommend someone in your area to do the tile cleaning and plaster work, if you like. PM me and I'll be happy to try!

Just a quick note from The Scale/Copper Stain Queen. If the scale has a slick glaze over it it is the hardest to remove and the last to come off if you do any filled pool treatments which may not work unless you want to spend a couple of years and hundred/thousands of dollars slow treating it with special sequestrants and lots of stainless steel brushing. Also your filter, any filter will load up quickly. I'm currently doing a semi-slow treatment using Jack's Magenta. After a good backwash my big 80 sq ft Quad DE filter is needing a backwash every 12-24 hours. Instead I switch between filter and recirculate for about 40-48 hours and run the Aquabot many hours a day with fine filtering bags, Nasty Bags, and switch them out a couple of times a day. It is a lot of trouble.

A Jack's Stain and Scale treatment could do some good but you can't use the pool while the treatment is in progress. There is a process using Jack's Stain and Scale treatment that is pretty complicated. Oldpooldad would be the expert on that.

If it were my pool, and the plaster could handle it, the fastest and cheapest way to get the stained scale off would be an acid wash. I've done my pool six times (two different plaster jobs) and I'm a granny. So if you want to do it yourself you can save some money but it is not fun.

BTW... I'm not doing the Jack's #2 Stain and Scale treatment because we need the pool to be usable.

I'm not doing another acid wash because my 14 year old plaster, still in pretty good shape, probably wouldn't be if a fourth acid wash was done to it.

gg=alice

The worst part of the scale/staining is below the tile, so what if I were to tape off the tile in order to avoid having the acid eat away the grout? What strength muriatic acid would I need, and how long to let the acid sit on the surface before rinsing away? I don't need to scrub it, only rinse it away, right?

Thanks!

I'm gonna let the experts comment more. In my case I just guesstimated on time left on, which was only the amount of time it took me to set the plastic flower bucket down and grab the brush, with a long handle. I did scrub with an appropriate natural bristle brush that swivelled. Many placed needed only light scrubbing after a sprinkle of weak acid solution. Some places needed more acid concentration and some even straight 3x.xx MA.

My pool plaster is blue so it is easy to see when you are overdoing it as the run-off gets darker and darker blue as more good plaster is being affected. You mainly want to go down just below the scale and leave as much plaster as possible. It is harder to do with white plaster.

For this last acid wash, summer 2008, I didn't hit the horizontal surfaces of the pool very hard, even on the acute slopes, because the scale was so uneven. You can lose a lot of good plaster in that situation if the scale is spotty with lots of good plaster exposed. I learned this lesson from starting out years ago on the top step. To this day I have some pitting. That's why I resorted to using a grinder to get the scale off of the steps.

gg=alice