Algae or scale or something else?

[gracepool]

Hi,
Our pool is 3 years old and we have not had a problem with it up to this year. The pH bounces up but I keep it in check with muriatic as needed. We're new to the forum and have a problem. I'm confused if it is algae or possibly scale.
FC = 5
CC = pool store says .1
pH = 7.2
TA = 90
CH = 330
CYA = 60
borates = ?
CSI = using calculator is -0.28
We have numerous small, typically smaller than a quarter yellow/brown spots on the walls. Some are in shade and some are in sun. Most do not scrub off. They seem to be in areas where the plaster is a bit rough. Chlorine tablets do not fully remove them and they reappear. I tried a small stainless brush and they do not fully disappear. I have not yet used an algaecide. I've been running the swg at 75% for 2 weeks for 8 hours with the filter. I just bumped it to 10 hours. I shocked the pool 2 days ago with granular chlorine 3#. That put my FC to 5 yesterday. It's still at 5 today. My daughter had a party last night with 8 friends. I was surprised the chlorine stayed up this morning. Now the pool is slightly cloudy. Any ideas or advice would be appreciated as the it seems apparent that I know more than the guy at the pool store but not enough to figure this out! Thanks in advance!

 

[dmanb2b]

Hi Grace...welcome to TFP

You're almost there with getting it. I would suggest you read through pool school, specifically regarding the test kit we recommend using as well as the sticky on how to shock your pool.

You stated that you shocked your pool with 2 bags of shock, but I doubt you raised you FC to shock level as is suggested by the chlorine/cya chart in pool school. Shocking is a process and involves raising your FC to a certain level and holding it there until the water clears and you experience no overnight FC loss. Only the will things come back to normal for you, it sounds like your SWG is fighting an algae outbreak, but it will never win. My advice, in summary is to arm yourself with a good test kit, determine you shock level, use poolcalculator.com to determine how much liquid chlorine you need to raise your FC to shock level and then keep it at shock level until your condition improves. Good luck

 

[gracepool]

Thanks! Do you think it's algae then? The part that puzzles me is that it won't brush off and the FC didn't drop overnight.
The recommended shock levels are very high. I assume we cannot swim in the pool until FC comes down to 5 or so?
We'll order the test kit so we can test for over 5 ppm.

 

[dmanb2b]

Hi Grace...many of us here swim in FC that is below shock level. At a CYA of 60 your shock level is 24ppm and some room for error on CYA testing and I would say you are safe in anything below 15ppm. The key is that you need to confirm your CYA level.

On the stains...sorry I missed that piece, you may want to post a pic here to see if the experts can help you identify the staining issue, but as to your statement on no overnight FC loss...just curious as to ho you are confirming that you did not loose less than 1ppm of FC overnight without a test kit that can measure FC accurately? Maybe your just using the DPD test?

Fron the sounds of your post, it does seem like the SWG is struggling to keep up with your FC demand at 75%, but is this where you normally run your SWG to maintain FC? I don;t want to send you shocking if the water is clear and you have no overnight FC loss, especially with your low CC level of 0.1ppm

 

[gracepool]

Ok...my bad. I'm only testing for total chlorine with my kit (DPD). I'm going to get a new one this afternoon so I can test FC and CC. CYA is confirmed at 60. I can't seem to get a decent picture of the stains/spots, but I'll keep trying.

 

[gracepool]

Update from pool store...Total chlorine 5.5, free chlorine 4.7. I orderd test kit from tf test kits.

 

[dmanb2b]

OK...for a CYA of 60 your target FC level is 7ppm. Be wary of pool store results though, but at least they gave you a nice round number to the nearest tenth, which does have some credibility. You need to worry when a pool store tells you your CYA is 61 or 59, not sure how they can test so accurately.

Anyhow, it is quite possible that you let your FC drop below 5ppm and maybe you are fighting an alage bloom, which shocking would help, but I'm not sure it will help your staing issue, given the trichlor tabs did not do the trick.

According to your pool store results your CC is 0.8ppm, so you are borderline in the range of needing a shock cycle...we like to keep CC at 0.5 or lower.

The TF100 is an excellent choice, you be amazed at how powerful you will feel knowing your water chemistry, coupled with using Jason's pool calculator to figure out dosages.

You may want to stock up on liquid chlorine/bleach while you wait for the test kit...again shocking is a process of holding your FC at a high (superchlorination) level for a period of time, it is not something you add to your pool. Shocking can be acheive by adding bleach aka liquid chlorine at a 6% concentration (Pool Store liquid chlorine is either 6%, 10% or 12.5%) or using what the pool industry calls shock, which is a marketing term for stabilized chlorinating powder. The reason we do not like to use stabilized chlorine is that it either raises your CYA level or Calcium level and most times, it's just not needed. To much stabilzer (CYA) can and will overstabilize your pool. Good luck

 

[Butterfly]

Hi gracepool and welcome to the forum

dmanb2b has given great advice

Congrats on ordering the TF100 test kit. It will be your pool's new best friend :-D

We have articles in Pool School for "How to Shock Your Pool", "How to Do the Overnite FC Loss Test", etc. which you will find helpful.

When you do the overnight FC loss test, make sure to first turn off the SWG

 

[gracepool]

Thanks for everything. Now I just await the test kit. Then I can accurately shock. With the higher chlorine levels we have kept for a few days, it appears that the little brown/yellow spots are starting to fade. I hope a good shocking will make 'em disappear and we won't lose too many days of swimming (due to shocking) with the season coming to a close in a few weeks!

 

[PaulR]

Ok...my bad. I'm only testing for total chlorine with my kit (DPD).

The DPD test (drops turn the sample red) can test for both FC and TC; use the R-0001 and R-0002, that gets you FC; add R-0003, that gets you TC. If you're using the OTO test (drops turn it yellow) that measures only TC. In either case the test probably only goes up to 5, though. It can be handy to have a test with a wider range.
--paulr

 

[gracepool]

OK, the TF100 kit just came and here are the results:
FC = 5
CC = 0
pH = 7.6
TA = 100
CH = 320
CYA = 35
The CYA is way lower than the pool stores were telling me. I did it twice to make sure. The pool calculator says to add 10 lbs of stabilizer. I'll add half that for now in a sock in the skimmer.

The CC says I don't need to shock, but the yellow/brown stains are still there. They have faded some with me running FC much higher than I ever have.

Any Suggestions? Maybe it is scale?

Also, it has gotten chilly here and I would like to put the solar cover on. Do you think that will be OK? I haven't put it on yet because I thought I needed to shock.

Thanks!

 

[PaulR]

The CC says I don't need to shock, but the yellow/brown stains are still there. They have faded some with me running FC much higher than I ever have.

Any Suggestions? Maybe it is scale?

The stains are fading with higher FC, therefore you should stick with the higher FC because that's working. (This means the stains are organic, not scale.)

The presence of excess CC means you need to shock; the absence of excess CC means you need to pay attention to other things in order to make that decision. (CC won't give you a false positive, but it can give you a false negative.) Keep shocking until the stains are gone.
--paulr

 

[gracepool]

Still shocking after 48 hours to around 20 FC! CYA is about 40. Lost 3 on the overnight test for FC both Sat and Sun morning. CC is almost zero. We did get an inch of rain but I did some rough calculations and for my 800 sf pool that would be about 500 gallons of rain (not enough to reduce FC much at all).
The water has and continues to be very clear. The remaining little yellow/brown spots haven't faded or disappeared any further since yesterday. I've used 13, 1.4 gallon jugs of bleach so far. Hopefully the overnight test passes in the morning!
It's a shame we can't go in as summer is almost over and the kids go back to school tomorrow!
Can I put the solar cover on it tonight as it is going down in the low 60's?
Thanks!

 

[frustratedpoolmom]

Have you tried holding a Vitamin C tablet on the spots to see if they react at all to it?

 

[gracepool]

FC held over night at 18. I will still hold higher FC levels for the week (12 -14). I guess I'll start to bring my CYA levels up to 65 -70 now. I'll try the vitamin C as soon as I can get some. Here's a pic of the discoloration of the floor in my deep end. It's more at the bottom of the picture. I wanted the pool drain in for reference of size. When the sun hits it, it is very hard to see at all.

 

[gracepool]

Just took off solar cover. Water is balanced and FC held at 12.5 for three days with cover on! Mustard algae is gone but discoloration at deep is still there. I crushed Vitamin C tabs, put in a sock and tied to my pole and brush. After 10 minutes, the stain is substantially lighter. Now what do I do? Thanks!

 

[Butterfly]

I suggest you read about the ascorbic acid treatment from Pool School: ascorbic-treatment-to-rid-pool-of-metal-stains-t2298.html

On the AA Treatment, some are using citric acid which is considerably cheaper. Also, I have found that my local Health Food store sells it for about $2.55 lb.

If you do decide to do the AA Treatment, I suggest you wait until your water temp and chlorine demand are lower.

Have you tried a pumice stone on the rough plaster/stained areas?