Green Cloudy Water

[pool962]

I let my pool turned to swamp over the south alabama winter. Started up 2 weeks ago and it goes from black to a light green cloudy water the first week and no changes the second week. It's been at shock level for 2 weeks with the pump running 24/7 with daily backwash and brushing. Most of the debris are out I assumed for I can only see about 3 ft. Could my 10 yr old sand be the problem?

25k IG Vinyl
CYA - 30
FC - 17
CC - .5
PH - 7.4
TA - 90

 

[JasonLion]

Welcome to TFP!

Your FC level looks good for your CYA level, so I would investigate your filter. You haven't mentioned backwashing the sand filter. You should do that, even if the filter pressure hasn't gone up, unless you have already been backwashing regularly over the last two weeks.

A sand filter can take a while to clear up a major algae problem. If it is working correctly you should be able to see a visible improvement each day.

If that doesn't help, it might be time to open up the sand filter and rinse off and resettle the sand bed. Old sand doesn't filter as well as new sand, but it should still be able to get the water clear, unless it has become completely clumped up inside the filter.

 

[pool962]

I glad to be aboard this site. I'm transferring from poolforum.
I have been backwashing daily. I haven't seen any daily improvement the last week. I might just have to cut the pipes and replace the sand today to see any improvements.

 

[JohnT]

I glad to be aboard this site. I'm transferring from poolforum.
I have been backwashing daily. I haven't seen any daily improvement the last week. I might just have to cut the pipes and replace the sand today to see any improvements.

Before you do that, I'd try a double dose of cheap clarifier along with a couple of extra days of filtering. I don't like a clarifier in normal use, but for cleaning up an algae mess, it can be helpful to a sand filter.

 

[pool962]

After reading some of the other posts and seeing some of the pictures on here, I'm beginning to think I might have mustard algae.

 

[JasonLion]

Mustard algae will die and appear to go away when you maintain the pool at shock level. The special problem with mustard algae is that it tends to come back after you lower the FC level back to normal levels. While it is possible that you have mustard algae, that wouldn't have anything to do with why your water isn't clearing up.

There are several problems that can cause a sand filter to not filter very well. The most common is the sand getting channelized. Another possibility is the main valve could be broken in a way that allows water to bypass the filter. Whatever is clouding the water could be so fine that the filter can't catch it.

How difficult is it to open up the filter? You mentioned cutting the pipes to replace the sand. If your have a top mounted multi-port filter without unions it can be a real pain to open up the filter. If you can open the filter easily, it is worth doing that and having a look inside to see what condition the sand is in. Badly clumped sand should be replaced.

 

[257WbyMag]

Are you absolutely certain that your CYA is, in fact, 30 ppm?

 

[pool962]

Yes, I tested for CYA every other day. I started out with zero CYA and added about 4lbs of stabalizer a 1 1/2 week ago. Tonight my numbers are:
CYA 30
FC 12.5
CC .5
PH 7.4

I added 2 jugs of bleach to bring it up to mustard shock level and I'm going to try to keep it at that level for a couple of days and see any improvements before I replace the sand.

 

[duraleigh]

Poll962,

I can't give you a precise, scientific explanation for what's happening in your pool. I can tell you that based on prior experience over the years and evaluating similar threads to yours that you are probably not using enough chlorine on a consistant basis.

What is your normal operating psi? How much psi rise are you seeing in your filter when you backwash? backwashing daily doesn't do much good if you are not getting a psi rise of around 20% or so.

How often are you adding chlorine? A green pool like yours should have constant chlorine applications....as much as three-four times daily. You should be testing and reapplying to keep your FC around 15ppm or so constantly.

When a pool is slow to clear, almost all of us start looking for other problems to be the cause. It almost always is the lack of consistant chlorine application.

PS - While it is very, very good for my refill business lol , you have no need to check your CYA level more than 4-6 times annually. Perhaps 2-3 to get it right at startup and then maybe once monthly at most during the swim season.

 

[pool962]

This last Sunday was the first time I let my FC level dropped below 17ppm because I got home too late to fool with the pool. I been keeping the FC at 19 along with backwashing and brushing all week without any noticeable improvement. I open up the filter to inspect the sand and it's not clumpy or channeled but seems normal. I going to go ahead and replace the sand since I got it opened to see if it will help. I haven't try the clarifier yet, though. It has been 3 weeks with the pump running non-stop. I'm at a lost here.

Here are latest numbers:
FC 19.5
CC .5
PH 7.5
TA 110
CYA 35

 

[pool962]

Here is the latest update. After I changed out the sand 3 weeks ago, we had about 10" of rain that night that put me back to square one with the test numbers, zero cya, zero fc, etc. I ran the pool non-stop at shock level for a week with no significant improvement even with the new sand. I then try some clarifier and there were noticeable difference everyday. The pool has been crystal clear the last week. Who would have thunk that all it took was a $10 bottle of clarifier to do the trick. It seems the dead algae were too small to be filtered out by the sand. Thanks guys for the suggestion here.

 

[duraleigh]

962,

I am pleased that your pool is clear. If clarifier worked for you I am pleased as well but it typically is not necessary. There are many. many stories on this forum (some of my own) that describe an algae-laden pool being cleared perfectly with just a sand filter (no clarifier).....in my case 6 year old sand....I just did it this Spring for about the 7th time.

I'm not posting this to refute your situation but the cause was something other than lack of clarifier. It's important that other new readers don't unnecessarily change their sand or look to sand filters as the reason their pools will not clear