My (huge) pool suddenly cloudy; dirt vacuumed last night has returned to the pool floor?!

[glarbman]

My wife designed and built a scary enourmous 75k gallon pool in our backyard, we opened it last June and it somehow worked very smoothly. I live in AZ so the biggest problem was dust storms, but the water has always been crystal clear, and SWG has taken care of the chlorine needs, just have to vacuum the dusty bottom and add muriatic acid quite a bit.

About a week ago, the pool water started looking cloudy (my wife calls it “milky”), we can still see the bottom of the deep end, but it’s still hazy in there, and not getting better despite me jacking up the chlorine and running the pump 24x7

My chlorine has never measured below 3ppm, and when this cloudy pool crisis began, the overnight chlorine test showed zero consumption. Since I have CYA 60 I’ve now increased chlorine to over 5 in case algae is involved. Also ordered a FAS-DPD so I’ll be able to get more accurate chlorine tests soon.

HERE IS WHATS DRIVING ME CRAZY, I vacuumed the bottom last night, it had decent amount of dust on it, but when I went to bed the dust was all vacuumed to the filter. Now today. 12 hours later, the dust has somehow spewed back on the bottom of the pool. This makes me think the sand filter has developed channels or something, I mean, I thought the dust was supposed to stay trapped in the filter, but it just seems like the filter isn’t doing it’s job! I am panicking and thinking of calling our Pentair rep since the filter is only one year old. I have never had any kind of algae in this pool, a pool store test from 1 month ago showed about 300 phosphates, but I ignore that because I keep proper FC.

IN SUMMARY, I feel like my filter is NOT doing its job, since the dirt I vacuumed up last night made it back onto the pool floor today... but it’s only one year old and I have no idea if the filter should need a “deep cleaning” by now... honestly I feel like deep cleaning the filter would be best bet, but I have no experience taking one apart, I’m really not good at handyman tasks like that, so majorly stressing out!!

FC 5+ (waiting to get my FAS-DPD test kit)
PH 7.8
Alk 70
Salt 3650
Calcium 300
PHOSPHATES 300
Borates 0

 

[mknauss]

Welcome to the forum!
When you get your FAS-DPD test kit, run an Overnight Chlorine Loss Test
Cloudy water is typically algae.
I assume you do large backwash amounts or you have a water softener for your fill water. Your CH is pretty low by AZ standards.
I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.

 

[glarbman]

Yep my FAS-DPD test kit should arrive Wednesday.

If it’s algae, i have a question: I have never SLAMmed this enourmous 75k gallon pool before! Will it be OK if I use my dual SWG to create as much of the chlorine as possible? I know the troublefreepool SLAM GUIDE says not to rely on your SWG. add lots of liquid chlorine all at once, but for my pool, it would require and obscene amount of liquid chlorine. Since I have dual SWGs, if I run them all day it ends up producing a heck of a lot of chlorine.. so I am leaning towards using that, if I need it!!

 

[mknauss]

You can -- but you will find they will not add all that much chlorine in relation to your SLAM level FC.

 

[JamesW]

Do you have a picture of the stuff on the floor?

 

[glarbman]

Do you have a picture of the stuff on the floor?

Gosh I don't have a picture right now. It's a brownish color, and was easily blown around like dust, so I totally assumed it was dust (since i have to deal with AZ dust storms, dust is the only problem I have experience with so far).
I'll try to take a closer look during daytime tomorrow.

 

[JamesW]

Was it olive green with yellow highlights?

 

[glarbman]

Was it olive green with yellow highlights?

No, looks more brownish. Also by the way, this “dust” seems to blanket the whole bottom of the pool... not just corners / shady spots.

 

[glarbman]

Spoke with my wife and confirmed, she brushed part of the pool just a few days ago, but it had re-covered with "dust"... yeah I think this "dust" must be some kind of algae since it keeps re-appearing without any apparent cause. I am going to begin SLAM process as soon as possible.

I mean, the alternative is that my sand filter is somehow broken and not "filtering", but, that doesn't make sense ... it is only 1 year old... it makes more sense that this is some kind of algae.

 

[duraleigh]

I would say about 98% chance it is algae. SLAM your pool and it will go away. Keep your FC at the TFP suggested levels and it will stay away.

You can not perform the SLAM or keep your pool at the correct levels unless you have an FAS/DPD test kit. Nor can you maintain your pool properly by relying on a pool store for your testing. Getting one of the two suggested kits and doing your own testing will keep the "dust" out of your pool.

 

[Katodude]

You must have a very nice and beautiful pool. Let me give you the best piece of advice you can get for free. But the TF-100 test kit and a speedstir. The links to buy are on the moderators signatures. It is the best $100 you will ever spend. Be prepared to spend another $50 a year to buy new reagents. It took me a couple of years to acquiesce for some dumb reason and now I kick myself for not having it sooner. Since getting one my pool is the best looking pool (water clarity wise) in the neighborhood.

Now a robot is also probably a good idea if you have dust storms but they are expensive so completely optional.

 

[glarbman]

So this Dusty looking pool (with dust "growing" on the walls, I now realize) probably has MUSTARD ALGAE right? There's just a very thin uniform layer of it this morning (which I've already brushed). I don't think it will show up well in a photo, is very subtle and sneaky.

If I can get my hands on a FAS-DPD today then I'll start SLAM tonight...

 

[Flying Tivo]

Mustard algae is very rare, just go for a normal SLAM, if it go's away then you are done! If not we can go from there!

 

[mknauss]

NO

FAS-DPD today

Not likely. FAS/DPD Chlorine & CC's test

 

[glarbman]

NO

Not likely. FAS/DPD Chlorine & CC's test

PROBLEM SEEMS SOLVED -- I raised chlorine level to SLAM level for three nights, brushing twice a day, and the pool looks great now. It was definitely some kind of evil algae but I nuked it long and good.

 

[JamesW]

Be extra vigilant about maintaining the fc. Don't let it get behind. Brush daily for a few days and then every other day.

 

[Casey]

Can we get a picture of the 75,000 gallon pool? Pretty please!!!!!!!

 

[Skenn81]

I was here to say what Casey said. Everyone is posting great advice and helping wonderfully but can we get a picture of this thing? I cant even imagine a pool that big in a back yard.

 

[BMK]

Glad you seem to be back in control. It's one thing to eradicate algae, but its more important to understand why it happened in the first place. Do that.

I also would love to see a picture your pool! How many bags of salt did you use to initially fire up your SWG??

 

[glarbman]

Came back after being away for 4 days and the pool still CLEAR but developed some brown “dust” again on about half of the surfaces! Wife said the pool had faint pond smell that she identify with the algae from before. I vacuum and backwashed, hopefully that will keep it from clouding the pool again. Chlorine is staying around 3-4 ppm but I’m going to try jack it up to 5ppm.

REGARDING SIZE OF MY HUGE POOL, I will post photo in a minute,
- Oh jeez I used 36 bags of salt to reach 3500ppm, it was honestly insane.
- I just tonight ordered 180 lb of boric acid, hoping borates will make the pH easier to manage.

Next I will be looking for a smarter pool robot. I have a Pentair Prowler 830 but it doesn’t follow any pattern and ends up missing at least half of the pool area, it seems to roam around randomly and I wish it was smarter. Also a lot of dust seems to escape and I’m wondering if getting a suction powered robot would be better at dealing with AZ dust storms? I would love to find an effective vacuum so I don’t have to manually vacuum the giant pool.