Milky Pool - no, it's not going to be as simple as you think...

[codertimt]

Okay guys, picture attached of cloudy pool. Also have sandpaper like scaling on vertical walls...starting about 6-8" below the water line. Used cal-hypo for chlorine last year with bleach shortage...so obvious high CH, TA and ph right... CH is 120. Only used 50 lbs of cal-hypo total which calculates to a max of 185 for my 18000 gallon pool, so the 120 reading makes sense with rain dilution over the winter. TA is 70, ph is currently 7.0. I've always opened to little or no CYA, I assume I have some flora or fauna that consumes it over the winter, but currently can't test as the cloudy water by itself quickly makes the black dot disappear. FC burns off quickly in the sun, so based on prior years, I'm assuming very little CYA, slamming based on 30ppm so been keeping 12ppm FC. Losing Chlorine overnight, so it's still killing stuff. Sand filter(new sand last year) is still capturing stuff and needing backwashed. I've been adding a handful of DE during the day and it needs backwashed more frequently...but there is no clearing happening. In the past after a couple days I could at least see shapes of debris in the bottom of the pool This year, it's just opaque after the first step on the ladder...and hasn't changed in a week.

So, given the scaling, there is obviously something going on, most likely related to calcium. I have to assume there is something else going on with my water chemistry that I don't have the ability to test for since it's happening at such low levels... My current plan is partial drain and refill and continue filtering and cross my fingers...Also thinking of dropping ph down to 6.5 or so to see if I can get the scaling to release some and brush away...otherwise not sure what else can be done water chemistry wise... Anyone have any ideas or opinions?

Numbers recap:
FC: 12 (SLAM)
TA: 70
PH: 7.0
CH: 120

 

[Texas Splash]

My biggest concern in your situation is what you said about not being able to get a good view on the black dot. Even with a green swamp we can do a good CYA test, so that's odd. An accurate CYA test is very important. But if you are really concerned about what appears to be scaling, I would just do a healthy water exchange and get in there at the same time to see if you can even do anything about it manually. If not, then the water exchange alone should help you with the SLAM Process and you can just press-on.

 

[Bperry]

Okay guys, picture attached of cloudy pool. Also have sandpaper like scaling on vertical walls...starting about 6-8" below the water line. Used cal-hypo for chlorine last year with bleach shortage...so obvious high CH, TA and ph right... CH is 120. Only used 50 lbs of cal-hypo total which calculates to a max of 185 for my 18000 gallon pool, so the 120 reading makes sense with rain dilution over the winter. TA is 70, ph is currently 7.0. I've always opened to little or no CYA, I assume I have some flora or fauna that consumes it over the winter, but currently can't test as the cloudy water by itself quickly makes the black dot disappear. FC burns off quickly in the sun, so based on prior years, I'm assuming very little CYA, slamming based on 30ppm so been keeping 12ppm FC. Losing Chlorine overnight, so it's still killing stuff. Sand filter(new sand last year) is still capturing stuff and needing backwashed. I've been adding a handful of DE during the day and it needs backwashed more frequently...but there is no clearing happening. In the past after a couple days I could at least see shapes of debris in the bottom of the pool This year, it's just opaque after the first step on the ladder...and hasn't changed in a week.

So, given the scaling, there is obviously something going on, most likely related to calcium. I have to assume there is something else going on with my water chemistry that I don't have the ability to test for since it's happening at such low levels... My current plan is partial drain and refill and continue filtering and cross my fingers...Also thinking of dropping ph down to 6.5 or so to see if I can get the scaling to release some and brush away...otherwise not sure what else can be done water chemistry wise... Anyone have any ideas or opinions?

Numbers recap:
FC: 12 (SLAM)
TA: 70
PH: 7.0
CH: 120

I’m not sure the CH number makes sense unless you refilled your pool prior to adding the 50 lbs of CH. Seems like it should be much higher.

 

[codertimt]

I’m not sure the CH number makes sense unless you refilled your pool prior to adding the 50 lbs of CH. Seems like it should be much higher.

My tap water tests out at 30...prior to the 50 lbs of cal-hypo, I don't believe any product I used(bleach or occasional tri-chlor tablet) would raise that. So old water or new, it should have been around 30 when I started...200 or so at the end of the summer...so with rain dilution, that 120 reading seems logical to me. I guess my reagents could be old and numbers could be wrong...I did QC my chlorine test...not sure how to QC the CH test...but again...the maths seem reasonable to me...

Regarding CYA, yeah the water is ridiculously opaque....I did decide to try again though and apparently the water is clearing somewhat because I was able to get results...previously with just pure pool water, the black dot would disappear at about the half full mark...now actually testing with reagent it's visible at the full mark, so as expected <30ppm CYA currently. So, currently just did a small water exchange...just to below the skimmer. I should perhaps do more, but I hate to pay for 9000 gallons of water because I'm being impatient... So new plan is to get water back in to get the filter back on...drop some acid(hah) and scrub the sandpaper walls while irritating my skin. Then just filter, filter, filter while keeping FC around 12 still...I'll keep the thread updated on progress...

Appreciate any and all thoughts...thanks and feel free to keep them coming...

 

[codertimt]

Update: I waited until I was sure things were under control before commenting again, as this has been a big of a struggle. After the second week with little to no difference in clarity. Maybe 2" clear depth vs 1". I had dumped in some muriatic acid to drop pH and try to release some of the scaling, but results were minimal at best. Acid was old, so likely didn't drop as much as I really needed. I did notice that after that brushing this particular time, for some reason my FC level dropped very quickly over the next day...that will be addressed later in my story-time. So I decided that even if the water was going to eventually clear, fresh water was going to be cheaper than bleach for the extended SLAM, so I decided on a half water exchange.. As the water dropped below my "scaling" line I noticed a couple things. 1, algae was yellow on the ladder and 2. The "sandpaper scaling" looked like colonies, but rock hard and glued to the wall. So I immediately thought mustard based on the color. Researching mustard algae showed it still should wipe off easily, but led me to a discussion of a phenomenon called Sand Algae. And it matched my symptoms exactly. Not sure what people on this site think of this theory, but the basic idea is with certain water chemistry, basically high pH and algae filled(which my pool was over the winter), even without an incredibly high CH, the free calcium in the water binds around the living algae as it extracts CO2 from the water Ended up with sandpaper like, glued on rock hard calcium covered algae colonies. And it makes sense that dropping pH to soften the deposits and then brushing ended up releasing fresh algae and eating up my FC the next day. Anyway, recommendations where to lower pH, etc...don't brush as it could damage the liner. I, however, have an already damaged liner from an accidental stagnant trichlor incident, so am not worried about some micro scratches. So out came a light scotchbrite pad and a few hours of manual labor. I would say 98%+ removal. Walls no longer feel like sandpaper, just the occasional rough spot. Quickly used multiple gallons of bleach trying to keep levels up while the pool was filling enough to vacuum...so again I assume I released alot of living matter with the scrubbing. Filled pool, vacuumed to waste, got CYA back up to 40, as the next day I used multiple more gallons trying to battle the sun. SLAMed at mustard levels for a bit to kick things off and vacuum and brush every day...and in a couple of days I could see shadows on the floor and a couple more I could see the liner pattern on the floor. Mostly clear at this point, already passes OCLT, so just final filtering for the most part, so hoping will be able to finish SLAM by the end of the week...will probably jump back up to mustard levels for another 24 hour period at the end and then let it drop back down....

So, TLDR recap, initial SLAM wasn't cutting it because I was apparently dealing with some mustard algae. Furthermore, hypothesizing that I had live algae encased in calcium that would have given me fits all summer if I had left alone... Or perhaps it was just normal calcium deposits...regardless, scrubbed away deposits(probably not recommended to scrub quite as hard as I did if you really love your liner) and increased FC after half water exchange and pool started clearing nicely as expected. I know there is at least one other post with "sandpaper on the walls" without having a high CH level, so maybe this might be helpful.

 

[Bperry]

That’s interesting.