Blotches

[Richard320]

My latest noob question:

Is it common to have blotchiness on the finish?

It's a white plaster pool, supposedly redone less than 2 years ago. I have no idea what's been done to it, and I don't have much confidence in the pool service that's been maintaining it for the last 15 years since my CYA is off the scale.

There are patches on the bottom that just plain look dirty. Brushing hard doesn't seem to change things, yet when I brush, the dirt I do raise appears to be the same color. On the steps of the spa section, it's sort of mottled. There's this sort of grayish film, with "bubbles" of whiteness. It's not slippery at all, and the finish is smooth, no scale. I tried brushing really hard in case it was just film, no lifting.

I searched the forum and tried rubbing a chlorine puck on it. All it did was leave chlorine puck on the step, which was easily rubbed away with my finger. One of the threads also mentioned setting a puck on the stain a while. How long is a while? 5, 30, 60 minutes? A week?

I'm wondering if it isn't just the nature of concrete? The patio and the garage floor aren't uniform, either....

The water is sparkling clean. We've used the spa end a couple times and had no skin irritation, red eyes, or ear infections.

pH is settled nicely at 7.4, Alkalinity was 130 this morning, Chlorine reads off the scale. I can't do anything about the CYA or Calcium right now, still under water conservation rules.

 

[polyvue]

Is it common to have blotchiness on the finish?

It's a white plaster pool, supposedly redone less than 2 years ago. I have no idea what's been done to it, and I don't have much confidence in the pool service that's been maintaining it for the last 15 years since my CYA is off the scale.

There are patches on the bottom that just plain look dirty. Brushing hard doesn't seem to change things, yet when I brush, the dirt I do raise appears to be the same color. On the steps of the spa section, it's sort of mottled. There's this sort of grayish film, with "bubbles" of whiteness. It's not slippery at all, and the finish is smooth, no scale. I tried brushing really hard in case it was just film, no lifting.

I searched the forum and tried rubbing a chlorine puck on it. All it did was leave chlorine puck on the step, which was easily rubbed away with my finger. One of the threads also mentioned setting a puck on the stain a while. How long is a while? 5, 30, 60 minutes? A week?

pH is settled nicely at 7.4, Alkalinity was 130 this morning, Chlorine reads off the scale. I can't do anything about the CYA or Calcium right now, still under water conservation rules.

Hi Richard, welcome to the forum!

It's common to complain about blotchiness... :-D

Was this the thread you referred to? help-please-stains-on-gunite-pool-with-pics-t15255.html

How extensive is the blotching? All over the bottom but not the sides? If you post a picture that sometimes helps with the diagnosis. How long did you leave the trichlor puck on the step? If only a few minutes, that may not have been long enough. Try the puck again for an hour or two and see if the stain/blotch fades. If it does, high levels of chlorine coupled with normal pool maintenance (regular brushing and vacuuming) and time will help. Some folks here have hastened this process by direct application of concentrated chlorine in the form of pucks, granules and 12% sodium hypochlorite. I don't have experience doing this but other members here can tell you the procedure.

Other possiblities: algae, metal stains, calcium scale. You can check for metal stains by the localized application of a vitamin C tablet. For more on metal stains read this. You mentioned that your chlorine and CYA levels are very high. Since too much CYA can tie up the available chlorine so that little or none remains to kill algae, there may well have been an algae outbreak in the past that left residue that wasn't entirely cleared from the pool. This is really the wrong time of year (in the northern hemisphere) for algae to flourish but that's also a possiblity, however unlikely. If you determine that you have algae growing, start with good test results and read this link. If you suspect calcium scale, test a small area by scrubbing it with a mixture of muriatic acid and water (1 part MA and 4 parts water.) If this works, do the same with remaining patches. Extensive areas of scale/dirt may require that you drain the water to work on them or do an acid wash on the entire pool.

For what it's worth, I too have a white plaster pool that was completed about two years ago, and from the first week after the pool was filled I noted several areas on the bottom where there appeared splotching -- darkened mottled areas that were resistant to brushing, extra chlorine and everything else I tried. They're still there -- I've just gotten used to them! :lol:

 

[PoolGuyNJ]

Poly and Rich,

Please post a pic of your splotches.

There are other causes too! Sometimes different thicknesses, overworking of the plaster when applied, wet gunite at application time and several other things can cause this.

Scott

 

[Richard320]

Okay, pictures taken. Let's see if the attachment thing worked. The blotches are on the spa step. The other is the bottom of the pool, but its hjard to get a good pcture. It looks like dirt, but it's not.

 

[PoolGuyNJ]

The 1st pic looks like it could have been rained on lightly before it hardened enough to fully absorb the energy of the rain drops falling.

The second pic looks like a little calcium build up. You can try gently rubbing a small section with fine (200+ grit) wet/dry sand paper. If it whitens up, it's calcium.


Scott

 

[Richard320]

The 1st pic looks like it could have been rained on lightly before it hardened enough to fully absorb the energy of the rain drops falling.

The second pic looks like a little calcium build up. You can try gently rubbing a small section with fine (200+ grit) wet/dry sand paper. If it whitens up, it's calcium.


Scott

It does appear to be calcium. I've been scrubbing while soaking in the hot tub, and it's definitely getting better. The odd color is probably metal staining the calcium. I get that purple endpoint on TA test, which might indicate the previous owner and pool service added something. Or.... the tablet floater that I removed was tethered to the wall with a piece of ~24ga insulated copper wire. Brilliant, huh? Copper wire as close as possible to the strongest concentration of Chlorine!

Well, it's warming up, so it won't be too much longer before I can attack the pool walls and floor too. It looks like a long-term project, just from the size of the area, but at least I know it is do-able.