Featured Newbie with yellow/black mold, stratospheric CYA.

AtlasAirborne

Member
Jul 7, 2021
8
California
Pool Size
18000
Surface
Plaster
Chlorine
Liquid Chlorine
Hey y'all, glad to join the party! We've just bought our first house with a pool and are trying to get our bearings.

FC: 3ppm
CC: 0.5ppm
pH: 7.7
TA: 135ppm
CH: 300ppm
CYA: 200ppm after proper testing ... 210ppm? See pic, below

Water looks crystal clear to slightly cloudy, depending on the day. No color to it unless I've brushed off some mustard.

I've just backflushed and hand-washed the DE filter, and added a little chlorine over the past week (less than expected, presumably because of the CYA?). It's only taken a single dose of [email protected]% to get it from 1-2ppm to 3ppm and it's stayed there the last few days.

We've been getting some mustard algae despite normal FC (because of the CYA?) and there's some black mold, a handful of spots and a patch ~2sqft, which have been there for some time.

I'm guessing we want:

- dilute down to nominal CYA levels
- rebalance (to what pH?)
- treat mustard mold with Yellow Treat + shock + brush
- treat black mold with black algaecide + shock + brush

What's the best order to approach these in? Can the mustard/black mold treatments be used simultaneously, or will we require two separate treat/shock cycles?

Is it worth taking a water sample my local pool store for a sanity check?

index.jpg
 
Last edited:

AtlasAirborne

Member
Jul 7, 2021
8
California
Pool Size
18000
Surface
Plaster
Chlorine
Liquid Chlorine
A local report has our ground-water depth measured at 88ft (date unknown).

Does that suggest we'd be totally safe for a drain/fill if it came to that?
 

AK-

Gold Supporter
May 11, 2021
364
Randolph, NJ
Pool Size
7000
Surface
Vinyl
Hello Atlas and welcome to TFP.

Nice to see that K-2006 in action :).

On the CYA. The measurement is logarithmic. You will have to use dilution to find an approximate value (dilution reduces precision). Check this out: Water Testing Instructions - Further Reading

Chlorine forms a weak bound with CYA. With you CYA level all your FC is in the form of chlorinated cyanurates that are still effective oxydizer, but not an effective sanitizer. The traditional recommendation of 1-3 of FC is based on water with no CYA when all your FC is an effective sanitizer. That is why we have the FC/CYA Chart
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
41,508
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I'm guessing we want:

- dilute down to nominal CYA levels
- rebalance (to what pH?)
- treat mustard mold with Yellow Treat + shock + brush
- treat black mold with black algaecide + shock + brush
Welcome to the forum.
The last two items -- please do not do. Yellow Treat is Sodium Bromide. That will make your pool a Bromine pool. A mess. That will require a drain. After you all ready drained it for the sky high CYA. Not good.
Black Algae (read Black Algae - Trouble Free Pool) is dealt with chlorine, brushing, and patience.

Follow what AK said, then come on back and we can provide some guidance. Read Draining - Further Reading
 

AK-

Gold Supporter
May 11, 2021
364
Randolph, NJ
Pool Size
7000
Surface
Vinyl
Regarding your shock question (sorry started answering before reading the whole thing)…

TFPC does not use traditional shock as a single action, we have a process called SLAM Process were you will bring your pool to shock level and maintain at it until all the nasties are gone. If you thing you have mustard algae please take a look at Mustard Algae - Trouble Free Pool

Anyway, it is impractical to SLAM at your CYA levels. I’m sure someone will help you with your drain/refill concerns.
 

Donldson

TFP Expert
LifeTime Supporter
Jun 12, 2009
4,969
NW Ohio
The last two items -- please do not do. Yellow Treat is Sodium Bromide. That will make your pool a Bromine pool. A mess. That will require a drain. After you all ready drained it for the sky high CYA. Not good.
And black algae algaecide is usually some combination of dichlor/trichlor and copper. Which would add more CYA back the water and the copper will potentially cause staining of the surface.

As an aside, I sometimes wonder if the copper staining is intentional in this particular case. You use a strong chlorine on the surface which will lighten the color a bit, then the copper stains it so it comes out looking a bit greener which might be easier to ignore on a blue surface than a white spot. But I'm just musing now. Important thing is to take those algaecides off the list. If you've got to put fresh water in then you'll want to start it off on the right foot.
 

AtlasAirborne

Member
Jul 7, 2021
8
California
Pool Size
18000
Surface
Plaster
Chlorine
Liquid Chlorine
Hi guys, thanks for the responses.

I'll get an accurate CYA value and update here when I can, and nuke those algaecide orders from high orbit.
 
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AtlasAirborne

Member
Jul 7, 2021
8
California
Pool Size
18000
Surface
Plaster
Chlorine
Liquid Chlorine
Took a diluted test today - 200ppm CYA.

Guess I'll want to exchange 80-85% of the water and top up CYA later if necessary?

Is there a reference document/flowchart for balancing a pool after heavy dilution (ie the order in which to balance parameters)? I've taken a look around but haven't turned anything up yet.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
41,508
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Test after fully circulating the new water. If a full drain and refill done then CYA can be skipped. Partial drain then do all.
Chlorine is king. Get at least 3 ppm FC in the water. Test pH and adjust to the 7's.
Recommended Levels
 
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AtlasAirborne

Member
Jul 7, 2021
8
California
Pool Size
18000
Surface
Plaster
Chlorine
Liquid Chlorine
Thanks mknauss, I really appreciate your (and everyone's) help - this would have been far more confusing and intimidating without this forum.
 

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bioguy

Well-known member
Aug 5, 2018
66
Whitehouse Station, NJ
Are you sure you're reading the CYA right? From the picture, I can't tell anything, you need a picture looking down into the tube to see if the black dot is visible.
 

Newdude

Gold Supporter
TFP Guide
Jun 16, 2019
8,761
NY
Does that suggest we'd be totally safe for a drain/fill if it came to that
Yes and no. The ground water table fluctuates a good deal. Heavy spring (recent) rains may have raised that significantly, or could still be working its way down deep.

It’s a really good start though and if it’s been dry by you it certainly puts the odds in your favor.

Also, the ground needs to be desert flat for that stat to really matter. Your property could easily be 80ft lower than the test site, a mile away, and you’d never realize it by driving it/ being there.
 

AtlasAirborne

Member
Jul 7, 2021
8
California
Pool Size
18000
Surface
Plaster
Chlorine
Liquid Chlorine
Are you sure you're reading the CYA right? From the picture, I can't tell anything, you need a picture looking down into the tube to see if the black dot is visible.

The photo was taken at the transition level (from visible to non-visible), just to show how out-of-span measurement is.

Yes and no. The ground water table fluctuates a good deal. Heavy spring (recent) rains may have raised that significantly, or could still be working its way down deep.

It’s a really good start though and if it’s been dry by you it certainly puts the odds in your favor.

Also, the ground needs to be desert flat for that stat to really matter. Your property could easily be 80ft lower than the test site, a mile away, and you’d never realize it by driving it/ being there.

In this case, I (thought I) got lucky - the test site is a block and a half away, so I was hoping I could rely on it somewhat. Sounds like exchange > drain/fill anyway, per TFP dogma?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
41,508
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Are you in the LA basin? It would be very odd to have a water table anywhere near surface unless you live right on the beach.
 

Donldson

TFP Expert
LifeTime Supporter
Jun 12, 2009
4,969
NW Ohio
Sounds like exchange > drain/fill anyway, per TFP dogma?
Dogma = "a principle or set of principles laid down by an authority as incontrovertibly true."

TFP does not have dogma. We base our information on scientific study and experimentation and everything is open to change if good data showing it to be incorrect comes in to play. In fact, the suggestions on the site have changed somewhat over the years because of this. You need to drain because your CYA is proven to be extremely high and replacing the CYA laden water with fresh CYA-free water will correct the problem, not because our word on it is the final word.

I'd just appreciate being a bit more careful with your words is all.
 

AtlasAirborne

Member
Jul 7, 2021
8
California
Pool Size
18000
Surface
Plaster
Chlorine
Liquid Chlorine
Are you in the LA basin? It would be very odd to have a water table anywhere near surface unless you live right on the beach.
San Gabriel basin, though it sounds like that doesn't change the conclusion.
Dogma = "a principle or set of principles laid down by an authority as incontrovertibly true."

TFP does not have dogma. We base our information on scientific study and experimentation and everything is open to change if good data showing it to be incorrect comes in to play. In fact, the suggestions on the site have changed somewhat over the years because of this. You need to drain because your CYA is proven to be extremely high and replacing the CYA laden water with fresh CYA-free water will correct the problem, not because our word on it is the final word.

I'd just appreciate being a bit more careful with your words is all.
My apologies, no offense intended. All I meant to convey was that I'd taken to understand that there is complete consensus on TFP that simultaneous drain/fill (ie exchange) is the safer option when DIY dilution is necessary.
 
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revitup

Gold Supporter
Bronze Supporter
Nov 30, 2019
546
Pawleys Island, SC
Pool Size
8500
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Dogma = "a principle or set of principles laid down by an authority as incontrovertibly true."

TFP does not have dogma. We base our information on scientific study and experimentation and everything is open to change if good data showing it to be incorrect comes in to play. In fact, the suggestions on the site have changed somewhat over the years because of this. You need to drain because your CYA is proven to be extremely high and replacing the CYA laden water with fresh CYA-free water will correct the problem, not because our word on it is the final word.

I'd just appreciate being a bit more careful with your words is all.
No offense to all the other fine people on this site, experts and just well-known contributors alike, but you Donaldson are by far my favorite. I read every posting of yours knowing I am in for a treat. I do not doubt it possible that this all may indeed end in tears!
 
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Donldson

TFP Expert
LifeTime Supporter
Jun 12, 2009
4,969
NW Ohio
I do not doubt it possible that this all may indeed end in tears!
Oh that? That's just because of the pH balance in my pool and my excessive sweating. That and those darn rom-coms... Don't they know that they were meant to be with the old salt-of-the-earth boyfriend and not their new rich metropolitan fiance? He doesn't love her the way she deserves! 😂

My apologies, no offense intended.
I understand, and did not believe it was intended. This industry is full of "do it this way because I said so" and "I do it this way because I always have and that makes it the right way" types of people and seeing TFP lumped in to that (even unintentionally) hurts. We really try to have good data to back up everything we say and do.
 
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AtlasAirborne

Member
Jul 7, 2021
8
California
Pool Size
18000
Surface
Plaster
Chlorine
Liquid Chlorine
Maybe this is worth another thread in a different section, but I measured 6GPM with the recommended Superior Pump 91330 1/3 HP through a 5/8" x 50' garden hose.

That's some 38hrs for a 80% water exchange... is there something obvious I'm missing that is bottlenecking the pump more than would be normal? Is it perhaps worth grabbing a couple of the 25ft 1-1/2" hoses? (I need a 35ft run) .

This industry is full of "do it this way because I said so" and "I do it this way because I always have and that makes it the right way" types of people and seeing TFP lumped in to that (even unintentionally) hurts. We really try to have good data to back up everything we say and do.
Ah, yeah, with that context a little defensiveness is completely understandable.
 

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