Algae or Silt. I'm sure for the 1000th time

[timh]

We bought this house last summer, so this is my second season with the pool. I have obsessively read the forums here and have mostly been using the BBB and recommended wisdom here. I've had a recurring problem with algae or pollen/SOMETHING. This has drove me nuts. The guy we had close the pool last summer did a crappy job and we opened to a black swamp full of leaves and seeds. Slowly, shock, the filter, and lots of netting cleaned it up.

I'm in MD and we had a few really bad weeks of storms dropping in lots of rain and with it god knows what else. I have been seeing greenish yellow stuff accumulating in dips and the corners. I would see this all along any non vertical surface. This stuff would accumulate in corners and seems and on the floor and sloped walls but not the vertical walls. I brought up the FC to 14 and brushed the whole pool. The water went from clear to dirty/greenish after brushing, nothing like the swamp we had earlier in the season though. I had remembered the same thing happening last year as well. I had assumed it was algae and shocked it and cleaned the pool thoroughly but it would return clumping in spots every few days or week or two.

This morning, I did a backwash and filter rinse. After setting it back to filter and doing a water test I noticed that all the sudden the floor around the return in the shallow end had that green stuff along the floor clumping in various spots and seems. Before backwashing the floor was clear. This got me thinking that something is wrong with the filter and that maybe the filter needs one of those deep cleans with the hose. Or possibly replacing the sand. (I know sand replacement is a bit of a religious topic around here) I would just do this, but the plumbing doesn't have screw on union joints so I'm doing some plumbing if I have to take the top off. Given how gross the pool was a month ago I can imagine that the filter is really full of Crud. I have been backwashing regularly.

I lost 1 PPM FC over night 0 CCs. Should I still see green specks appearing at 13FC and 30CYA? Am I wrong to believe that I should not see new algae on the floor at 13FC/30CYA? I'm color blind so telling green and yellow apart is not easy. My wife said the spots and stuff are greenish yellow (helpful I know...) could this be mustard algae? I understand it requires higher FC levels to kill, but shouldn't it still at least be using up more FC than I'm seeing? I believe my pool is getting dirtier by running the filter longer.

We have a LOT of trees in and around our property. So pollen isn't an impossibility. What would still be greenish at that FC level?

Confused, frustrated, and ready to find money to fill this hole in...

30k gal vinyl
Sand Filter
CYA: ~30
FC: 13
CC: 0
Ph 7.5
CH was ~100 a week or so ago
TA was ~100 a week or so ago

 

[timh]

Also one last addition. My understanding is that algae require sunlight to grow. Should algae get visible worse overnight? I mean from a few small greenish spots to OMG those are streaks of green now.

 

[Casey]

If this were my pool, I'd bump the shock level up to 20ppm n hold it until the water is crystal clear, you lose less than 1ppm over night (I'm talking .5 or less). Algae needs sunlight to grow so any trapped algae in your filter should just be backwashed out. The filter is doing it's job.

Keep shocking!

 

[timh]

I dumped in the bleach I had left. Brushed the whole pool, stirred it up real good, added some DE to the filter and then tested the water. 19FC. Checked it again this morning, 19FC 0CC. I'm still seeing this stuff appear overnight... If it passes the test it's not algae right?

[attachment=1:25o4d83t]shallowend.JPG[/attachment:25o4d83t]
The deep end is still pretty cloudy, I know the filter just has to work on that.[attachment=0:25o4d83t]deepend.JPG[/attachment:25o4d83t]

 

[timh]

I dove in today and sucked out gook from the floor. After it settled it looked and felt like very fine sand and dirt/debris. I'm going to keep the CL level elevated, but let it slowly come down, until I can crack open the filter this weekend.

Anyone have ideas on why dirt would be returning from the filter? I've heard cleaning the sand and I've heard the spider gasket could be at fault. Neither looked to be terribly difficult repairs. Should I just go ahead and replace the gasket while I've got the filter open?

 

[mbishop]

I could have written your post as I'm going through the same thing. Pics look just like mine also but I had more of it. I noticed it two days before leaving on vacation last week and came back to a mess. I was stumped because my numbers were right on and water was clear(until I brushed), no overnight loss and no cc's. Still had that gunk on the pool floor and it scared me. So, I went crazy on it to the point my fiance thinks I've lost touch with reality. I went and bought a bunch of bleach and began brushing like a mad woman(at least a dozen times a day). I kept DE in my sand filter and backwashed and replaced as needed(at least 5 times a day!). Three days back from vacation and hitting it hard, I got my sparkly pool back and am nearing my shock process as I only see a tiny spot that shows up now but I pounce on it like a rabid hyena. We've had tons of rain so I don't know if it was dirt or algea. All I know was I didn't want it there and it was covering the whole floor by the time I got to it and looked plain gross. It didn't seem like my filter was doing anything at all but did awesome once I added the DE. It looked greenish, reddish, rusty looking and not slippery at all. It clouded up green when I brushed it. I could turn the filter off and pool be clean but next day 15 minutes after turning it back on, BAM! There it is! So, if that's it, just keep hitting it hard and use the DE to help move things along and brush like you're training for the Olympics.

 

[duraleigh]

Your pics look like algae to me. Here's when you stop the shock process....

1. Your pool water is sparkling
2. Your CC's are .5ppm or less
3. You can hold your FC overnight without losing more than 1ppm.

You haven't passed #1 yet and I think you are too quick to blame your filter.

If that was my pool, I would hold FC constantly at around 13- 15 ppm and brush the stuff up into the pool water to let your filter capture it and to expose it to more chlorine rather than let it lie on the floor.

If you can truly feel grit, then you may have some filtering issues but the overwhelming anecdotal evidence here on the forum is you have not held your FC high enough and long enough.

1. Keep your FC up

2. Brush

3. Vacuum

4. Clean your filter as necessary.