Green on bottom, chemicals all in range, is filter working?


Apr 10, 2010
Metairie, LA
BBB has been working GREAT for me till the last few weeks. The water temp is constantly in the lower 90's as much as 94. I guess that is what I get living in the "deep" south! I have been checking the water myself and have also been bringing a sample to the pool store to see if my results are accurate. The latest...
FC 3
TC 3
PH 7.4
TA 80
CYA 40
Phosphates are high, can't remember the number

I am having green patches on the bottom which eventually cover the entire bottom in a couple days. I have added more bleach to shock but it doesn't seem to help. My concern is my sand it working properly? When I hook up my vacuum to the skimmer it does a great job of cleaning the bottom. As soon as I remove the hose from the skimmer I notice green water coming into the pool via the jets. While the vacuum is attached I don't notice this but as soon as I remove it, maybe cause it gets better water flow into the filter, green comes out. Then I will backwash (2 minutes) and rinse (1 minute), which I do very often, but I still notice a little green coming out the jets then it seems clear. Last evening I removed the multi-port direction valve from my sand filter to see what is going on. The lever that you move to backwash, rinse, filter etc seems to barley move the bottom plate (when you press it down to change positions) that touches the gasket to direct the water flow. I am not sure if the spring pressure is proper cause you can't really see any difference when you push down the lever. My first thought was that the water is not being filtered properly, almost like it is recirculating. I stuck my hand in the filter and looked at the sand. It is perfectly white, looks good. I did change the sand back in April, 300#'s which is what is recommended. I am taking the multi-port direction valve of the sand filter to the pool store today to see what they say.
Sorry for the lengthy note. I actually have been up since 2am with this on my mind. I want my crystal clear water back!!!

Any suggestions??




LifeTime Supporter
May 30, 2008
NE North Carolina
I am not sure if you have a filter problem or not. I can tell you, though, that you should be shocking your pool since you have algae growth. I would vacuum to waste to remove as much algae as possible and then shock until you pass an overnight FC test.

I seem to remember reading or being told in the past that sand filters are not fine enough to filter out algae. Could that be the issue?


Mod Squad
TFP Expert
LifeTime Supporter
Apr 17, 2010
East Texas
Take that pool to shock level and HOLD it there and keep running the pump/filter.


LifeTime Supporter
Jul 11, 2010
England, UK
Did you take the MPV gasket to the pool store? What did they say?

Our gasket gave us trouble recently when it didn't seal properly, partly because the central pin on the handle was coming out, and partly because a couple of large paint flakes got wedged in there (don't ask). The effect in our case was the water started trickling away to waste, but that was noticable fairly quickly.

I'm puzzled by the fact that you say it vacuums just fine, and then only spits green back into the pool when you stop.


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
Algae (which you have) is ALWAYS a water quality issue. It SOMETIMES can be exacerbated with a filter problem but never lose sight that it is poor water quality that got you there in the first place.

As others above have suggested, Shock your pool properly (pool school has a good article) andyour clear water will come back.

PS - You can keep that water temp much cooler on the cheap if you decide. Search Pool cooler, fountain, etc. on this forum.[attachment=0:y46rujrm]poolcooler.jpg[/attachment:y46rujrm]



LifeTime Supporter
Jun 18, 2010
San Antonio
I have a sand filter and yes they sometimes do not filter out the fine particles. I had an algae problem when I opened my pool this year. I killed it off and tried to vacuum to filter, but stuff kept coming back through the return. In my case it came back as I was vacuuming. I was told to vacuum to waste until I got all that settled junk out. I did and this worked great. The filter works great now. If that does not work you may want to check your filter to be sure you do not have channels in the sand. But as Dave said you need to kill the algae and you do that through shocking.


Apr 10, 2010
Metairie, LA
Thanks for all the advice. Come to find out nothing is wrong with my filter just with the water temp around 94 I really needed to run my pump on high speed for 12 hours a day, I was doing only 8 and some of that at low speed. I did keep at shock level for a couple days and vacuum to waste and everything is good now! I am very pleased with the water quality. Now I am going to research regarding cooling the water down as Dave S. suggested.
Thanks again to all that replied...good advice!


LifeTime Supporter
May 23, 2007
SE Minnesota
I also use a skimmer sock, it catches the fine particles. I just rinse it out when I turn the pump off for the day.
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