Black streaks in new plaster

[AS1518]

Pool plaster question -

We recently redid our pool plaster (completed in May) and are using the same company for weekly service this summer. Twice in the last 2 weeks, we’ve noticed black streaks in the pool after they’ve been here (at least this week we’re certain it wasn’t anything we did since we hadn’t used the pool since they were here on Tuesday, and definitely hadn’t noticed the new streak when we were in on Monday). The first time it happened along the steps (picture below), they came out to pumice it off as it doesn’t just rub or brush off easily (not ideal probably in hindsight because of very superficial scratches it left, but service manager said it was way up go) and blamed that our hose must have caused the issue, but now there’s a new huge black streak on the wall and definitely no hose by us over there. Anyone know what this might be or any experience? We’re at a loss and want to try to be informed when we’re talking to the company so they don’t just keep blaming us. Anything with integrity of plaster? We’ve lived here several years and several summers with old plaster and never once had anything like this.

 

[Poolbreh]

It looks like it’s from pool equipment. See what equipment they are using that’s black. They used to make a piranha net with a black rim, if you net off the bottom it would leave these black streaks.

 

[Bperry]

Looks like a crack with algae forming in it, but hard to believe that would be what it really is.

 

[AS1518]

It looks like it’s from pool equipment. See what equipment they are using that’s black. They used to make a piranha net with a black rim, if you net off the bottom it would leave these black streaks.

Any tips for cleaning that? Last time it was the steps they used a pumice stone but that left superficial scratches. I’m also confused if it’s related to the new plaster? I can’t imagine they’re going around on weekly cleanings leaving marks but I’m confused.

 

[AS1518]

Looks like a crack with algae forming in it, but hard to believe that would be what it really is.

When it first happened on the steps it was able to be removed. It all feels smooth so we’re confused.

 

[Toxophilite]

Almost certainly, it's a metal scrape from either the brush pole or head. Some metal transfers. The one on the step is a dead giveaway, where someone leaned the pole into the ledge for leverage to brush away on the lower step. If side wall same consistency, look at your (or their) brush head. I did that to my coping, but could lightly sand off.

 

[AS1518]

Almost certainly, it's a metal scrape from either the brush pole or head. The one on the step is a dead giveaway, where someone leaned the pole into the ledge for leverage to brush away on the lower step. If side wall same consistency, look at your (or their) brush head. I did that to my coping, but could lightly sand off.

Ok thanks. I’ll talk to them again. It’s the second week in a row it’s happened. Does it seem like a function of new plaster? In 4 previous summers with our old plaster this never happened.

 

[Toxophilite]

That's a mechanical mark, not chemical. If you take a piece of aluminum, you can draw on cement because the rough cement grinds aluminum , which embeds. Not sure of remedy, but do not like the idea of sanding on plaster. If the the new plaster isn't fully cured, it may be easier to transfer, but either way, some pole and head needs looked at, or, they need to be more careful.

 

[AS1518]

That's a mechanical mark, not chemical. If you take a piece of aluminum, you can draw on cement because the rough cement grinds aluminum , which embeds. Not sure of remedy, but do not like the idea of sanding on plaster. If the the new plaster isn't fully cured, it may be easier to transfer, but either way, some pole and head needs looks at, or, they need to be more careful.

Agree about them being more careful. It’s very frustrating.