Pool is Still Green After a Week of Trying

[SMT03]

Hi, we are new to the BBB method. I have been coming to TFP for advice for a year or two and decided to take the plunge (and hopefully control of our old pool) this season.

We started out with an initial algae bloom in late March, and followed the advice for "Turning Your Green Swamp Back Into a Sparkling Oasis" and it worked great within two or three days - turning the milky blue within 24 hrs and filtering out after that.

As you can see from the test results, we have an obvious problem with CYA thanks to eight years of pool store chemicals and adding "optimizer" at their suggestion. A couple of weeks ago, we decided to do a drain and replace in hopes of lowering the CYA. We drained a little over half the pool and refilled. Unfortunately, we now have two problems...the CYA is still reading 100+, and since we did not want to pour chlorine in the pool just to drain it into the yard we have another algae bloom. The unseasonably warm April/May in the southeast has not helped.

Last Friday, we started the process to get rid of the algae using the method from this site that seems to work for everyone else, and worked for us once. Assuming the CYA was 100, we brought the FC level to 39 (which worked for us in March) and kept it there through the weekend. Because the pool never turned the milky blue color, we have been bringing the FC level back up to 39 twice a day (morning and evening). We are not seeing a lot of movement between readings (the lowest the FC has been in the past week is 32).

The problem is, the pool is still green - it never turned the milky blue. The algae seems to be dead, it is settling on the bottom, but the general color of the pool is still green. We are not seeing a pressure increase or a lot of algae when we are backwashing - it just seems that everything is still in the pool. Is it possible that the algae is dead even though it appears green?

I told my DH that while he vacuums the pool in hopes of speeding up the filtering process, I would pose the question to the experts. After eight years of fighting it, if this pool doesn't become "trouble free" soon he might lose it.

FC: 36.5
CC: 1.5
pH: 7.5
T/A: 120
CH: 450
CYA: 100+

 

[kenmar]

welcome, you came to yhe righy place!

Even though your cya is reading 100, it may be much higher. I would work on lowering your cya to a more manageable level first.

 

[Isaac-1]

If you get the CYA under control everything else will flow from there, if you have a CYA test in your test kit, try diluting a sample of pool water 1 to 1 with CYA free water (tap water will do) and multiply the result by 2. This will give an idea of just how high that + part of 100+ really is.


Ike

 

[JasonLion]

It is very very difficult to fight algae with CYA over 100. One issue is that the PH test doesn't work at high FC levels and if the PH gets too far out of range the chlorine won't be effective. If that PH result is from a test done while FC was in the 30s then it is going to be way way off of the actual PH, which will be quite a bit lower than that. By far the best thing to do is to replace water until you can get the CYA level down below 100.

Algae can sometimes still be green even when it is dead, though usually it turns gray or white. It will never be as bright/saturated a green as it was originally. On the other hand, if the algae is all dead, the filter should be making visible progress on clearing up the water each day. Sand filters can take quite a while to completely clear the water, but there should be visible progress unless the algae is still alive or the filter isn't working somehow.

From your description, it does sound like there might be something wrong with the filter. If there is visible algae in the pool the filter pressure should be going up noticeably day by day. Can you describe the waters appearance in more detail? Is it very murky, or just slightly cloudy?

I suggest you do the CYA test again, but this time mix equal parts of pool water and tap water together, do the CYA test on that, and multiply the result by two. That won't be nearly as precise as the regular CYA test, which is already not all that precise, but it will give you an idea if CYA is still somewhere around 100 or is 200+.

 

[SMT03]

We tested and balanced the pH to 7.4 before we brought the chlorine level up, but that was a week ago so all I have to go on now are the high FC readings. After we did the half drain and fill I tested the CYA and once I realized it was still reading over 100 I did the tap water dilution method - that gave me a reading of 50, so as far as I can tell it is closer to 100. I am hoping that the high amount of algae in the pool at that time was making the reading higher, too. We have a low lying yard with drainage issues, and with all the rain we have had recently we are not ready to do another drain and fill.

The green color is definitely not as brilliant as it was last week - it is more of a yellow green. The algae that was vacuumed from the steps was yellow. The water is not murky - probably more "slightly cloudy". I can see almost to the bottom in the shallow end. We thought there might be a problem with the filter because there was some sand pooling up when we vacuumed to waste. We checked the filter this afternoon and it seems to be working fine - the sand was not clogged with algae and we are getting a good flow. The "sand" coming out of the vacuum hose was much finer than the filter sand, and I think we determined it was part of an on-going plaster issue (the issue being the 30 year old plaster is flaking and needs to be refinished and the bank account is not ready for that).

Since the algae does not appear to be getting worse, I guess we can give it another day or two to see if there is visible progress. Should I keep the chlorine at shock level while we wait? Since the chlorine has not been shifting dramatically (thanks to the high CYA :-D ) I don't think it will require any more to keep it at 39 than it would to keep it at 12, I just don't know if it should be kept that high for so long.

 

[JasonLion]

Your description fits with the algae all being dead and the filter simply taking a while to clear the water. Your filter is small for that pool and your pump is large enough to be interfering with filter efficiency a little. If the filter is working you should see a visible, if perhaps small, improvement in the water each day. If you are not seeing an improvement each day, it is time to try something new like adding a little DE to the filter.

 

[SMT03]

Thanks Jason! I was telling my husband today that I heard you could add DE to a sand filter to help it. We used to have an extra bag of DE laying around because our previous filter was DE. Ironically, I think it got thrown out because after fighting that filter for 5 years we replaced it and were ready to be done with all things DE. Oh well, If I remember a bag of DE wasn't that expensive and it is worth a try.

The filter was bought at the the recommendation of our local PB - who we thought was our friend until I found this site