Help with two different plaster issues/stains?

[Kevink]

I recently purchased a home with a 7-year old in ground pool with a salt water system. For the most part the pool and equipment are in very good shape, except for a high calcium hardness reading and two different kinds of plaster stains.

First my current test results:

FC = 5
CC = 0
PH = 7.2
TA = 70
CH = 650
CYA = 60
Salt (per test strip) 3080

When I first moved into the house (about 1 month ago) the PH was over 8.0, TA was 100 and the FC was at 10. For all I know, this may have been the situation for quite some time because the prior homeowner had the water tested at the local pool supply store about once every 2 weeks or so.

Anyway, thanks to this forum and the TFT test kit I was able to monitor the water on a daily basis until I got it (somewhat) under control. I definitely intend on fixing the CH as soon as I get the chance to drain some of the water and then refill it. The CH of my source water is 50ppm so partially draining and refilling should help dramatically. I currently have calcium scaling on the tiles and at other places at the waterline.

Now for the plaster issues:

I've got dark and blotchy type stains near two of my returns as seen in this pic:

Some parts of the stain appear to be brown (like dirt, especially around the perimeter of the return), but for the most part they're just dark gray (at least to my eye). I tried vitamin c in a sock and it seemed to lighten it, but very little. I also tried a pumice stone, but that didn't do anything. I did not try a chlorine tablet because the FC was super high for quite some time and that didn't seem to lighten anything.

I have an attached hot tub with a waterfall, but the plaster in the tub does not have any of this staining.

The second issue with the plaster are these white marks (see stairs especially) which are pretty much everywhere throughout the pool on the walls and floor (but nowhere near as prolific in the hot tub):

Here is a close up of a landing which is under about 6 inches of water:

Neither the stain or the white marks are rough to the touch. During the day in direct sunlight, you really have to look good to even spot them. It's only in the morning or at dusk when you can see them very well.

Any who, I'm thinking that the aggressive water had something to do with both of these issues? And then the next question of course is, what can be done about them?

 

[Kevink]

As for the white marks, I also noticed lines or striations near the water line directly under the tile as seen in this photo (ignore the dark mark in between the pool light and the sun - that's a reflection of a tree in my backyard):

It's a little hard to see, but if you look to the right of the underwater light and go up a bit diagonally, you'll see the white lines I'm referring to. Interestingly, this is the route of the Polaris when its cleaning the walls on that side. I have no idea if it has something to do with the plaster discoloration, but I figured I'd mention it.

 

[Richard320]

I recognize that!

The bad news is the white "stains" are the actual plaster. The blue-grey stuff is scale. When it's not under water, it looks tan. Compare to this:

It looks worst when overcast or just before sunrise. In full sun, it's almost invisible.

The quick fix is drain the pool and have it sandblasted or acid washed. My fix has been to drain and refill a few inches at a time to lose a lot of the CH (I peaked at 1100 last year), keep TA about 50-60, and be obsessive about maintaining CSI around -.5; never above zero. Lots of brushing with a wire brush. After 8 months, it's about halfway gone. It is strange, but expected, to see CH climb even when you haven't added any water. I add a cup or two of acid about every other day.

 

[Kevink]

Thanks for the response.

So if I understand you correctly, most of my pool is covered in scale and the white is what the plaster should look like??

Time to learn about CSI....

What happens if I use acid and a steel brush, or is that something I don't want to do?

 

[Richard320]

You don't want to do. When I had the water level down in the spa, I put a few drops of acid on some scale on the top step, and it fizzed. Then I thought - Hey! Easy to really scrub it now! Now I have gouges in the plaster on the top step. More traction, but no longer smooth.

 

[1051dvl]

Perhaps my photos don't show it very well (documented in this tread scaling-t35405.html), but your situation is very similar to what I'm dealing with in a recently re-plastered pool. In looking at my chemistry log, it's not clear how I got here, but I've concluded that I'm dealing with scale of some sort.

After originally leaving a chlorine puck on one of the spots for about four hours, I saw dramatically lightening. I then incorrectly concluded it was organic and went about a major shocking exercise. Unfortunately, no change after the shocking. Pool store guy suggested it was the low PH in the puck that was causing the lightening, not the chlorine, and I think he's right.

So (and don't laugh....), but I've started a systematic attack plan of placing 5 pucks a few inches a part in the pool in one section at a time, leaving for 3-4 hours, then shifting to the next area with the idea that I'll eventually cover the entire floor surface (haven't figured out how to get at the side wall issues). After a few days, I've covered about an 8'x8' section -- a long way to go on a 40'x20' pool! But it does look tons better -- not perfect milky white, but the stains don't jump out at you as before. I just hope the lightening effect lasts...

PS - I've turned off my SWG for now as the 5 pucks seem to maintain the FC in the 7-ish range.

 

[Kevink]

You don't want to do. When I had the water level down in the spa, I put a few drops of acid on some scale on the top step, and it fizzed. Then I thought - Hey! Easy to really scrub it now! Now I have gouges in the plaster on the top step. More traction, but no longer smooth.

I was thinking of adding acid to the water using either a pvc pipe or one of those out spot removers I saw on Amazon and then use a wire brush. Is this not a good idea? I definitely don't want to gouge the plaster.

 

[Kevink]

After originally leaving a chlorine puck on one of the spots for about four hours, I saw dramatically lightening. I then incorrectly concluded it was organic and went about a major shocking exercise. Unfortunately, no change after the shocking. Pool store guy suggested it was the low PH in the puck that was causing the lightening, not the chlorine, and I think he's right.

The puck is something I have not done, but now after reading your thread I think I'll give it a try.

Do you have a pool cleaner? I ask because I noticed in one of your pics there are striations in the stain which I also have in my pool, especially on the walls. I'm thinking the pool cleaner's wheels have something to do with those.

 

[Richard320]

You don't want to do. When I had the water level down in the spa, I put a few drops of acid on some scale on the top step, and it fizzed. Then I thought - Hey! Easy to really scrub it now! Now I have gouges in the plaster on the top step. More traction, but no longer smooth.

I was thinking of adding acid to the water using either a pvc pipe or one of those out spot removers I saw on Amazon and then use a wire brush. Is this not a good idea? I definitely don't want to gouge the plaster.

It won't work. The first swipe with the brush will disperse the acid.

I use a stainless steel pool brush to brush my pool. I have a smaller, coarser "algae brush" that I use on the worst spots. Usually I'll use the algae brush by hand when I'm swimming in the pool, which is why the steps and the spa are cleanest; they're easier to reach. Other than that, it's just keep the CSI down and let the acid do its thing ever so slowly. My assumption is that brushing the scale leaves microscopic scratches in the scale, which increases the surface area. More surface, faster dissolving. I figure I should have the scale all gone about the time it's time for a replaster!

 

[1051dvl]

Do you have a pool cleaner? I ask because I noticed in one of your pics there are striations in the stain which I also have in my pool, especially on the walls. I'm thinking the pool cleaner's wheels have something to do with those.

Yes, I have a Polaris 280 and I had that theory as well, but I can't see how the fairly soft wheels of the cleaner would cause the issues (especially when brushing with the wire brush seems to have no effect). I think it had more to do with the differences in the final plaster finish caused by the varying trowel techniques -- the softer areas being more susceptible to the scale?

As for your suggestion about using MA through a PVC pipe, I agree with previous poster: I tried it, but it doesn't work (and it was a little stressful for me holding the pipe and pouring, even with gloves). I did have some success on the steps -- just pouring my regular maintenance dosage directly on the affected spots on the steps without the pump running, letting it sit still there for a several minutes, then attacking with a wire brush.

After reviewing many threads here, I'm convinced that what we're both experiencing is a major issue with white plaster, but not sure the cause. I feel I did a good job on the brushing at start up and my chemicals were reasonably in-check during the early curing stage, so not sure how this happened.

As I said, the puck approach is working -- although very slowly, 3" at a time! The wire brush alone doesn't seem to do anything for me. Again, I'm hoping someone on the boards can give me confidence that the stains won't come back!

 

[Kevink]

Yes, I have a Polaris 280 and I had that theory as well, but I can't see how the fairly soft wheels of the cleaner would cause the issues (especially when brushing with the wire brush seems to have no effect). I think it had more to do with the differences in the final plaster finish caused by the varying trowel techniques -- the softer areas being more susceptible to the scale?

When I was looking at the pool the other day, I noticed my Polaris climbing the wall and taking the exact same path as the striations in the stains. There's even a slight curve at the beginning of the striations which is exactly what the Polaris does as it begins its ascent up the wall. My thinking is that the continuous and repetitive path of the Polaris (up the wall) doesn't allow the scale to build up at those points. Just my theory anway...

I've got a chlorine puck on part of the stain....we'll see what happens in a few hours...

 

[Kevink]

It won't work. The first swipe with the brush will disperse the acid.

Dang it... What about using something like this out spot thing I saw:

http://www.youtube.com/watch?v=QYrXjIesf28


Anyone use this or something like it with acid? Would this thing filled with acid harm the plaster?