Green, Green, Go Away!


New member
Aug 22, 2007
rochester, ny
We just returned from a 4 day vacation and found our new pool to be green! I took a sample of the water to the pool store and spent $80 to get chemicals to fix the problem. To no avail. I have shocked, backwashed, vacuumed, backwashed again, etc. etc. Tonight we tried adding bleach and these are our current readings....
FC= 2/4
PH= 8.4
TA= 180-240
CYA= 100-150

Can someone help us. I am getting very, very frustrated. This is our first pool and we are supposed to be hosting a pool party next week and It would be highly embarrassing if they saw the likes of this pool water.



LifeTime Supporter
Apr 5, 2007
Joliet, Il.
Hi Brad...welcome to the forum :)

Your persistence will really pay off when shocking. You first need to get a full set of test numbers (with CYA). Then determine what your shock level is (the higher the CYA the higher the shock level needed). After this you need to KEEP your chlorine levels up at this level. IF they are no longer at recommend shock levels and may only be keeping algae at bay, and not killing it. Last is to KEEP the levels up even after the pool has cleared...only stop once your chlorine doesn't drop overnight (from late afternoon until early morning). According to chemgeeks CYA chart you need a shock chlorine level of 46.7 for a CYA of 120. Your gonna need alotta chlorine!

(editadd:) But with that high of a CYA your going to have a tough fight on your hands. A partial drain would be your best bet...then reevaluate where your numbers are at and make the needed adjustments. While your shocking...I'd also bring another sample to different pool store to verify the test results.

A newbie guide to fighting cloudy or green water, this thread may help you get started on your fight!

I'm curious what the numbers were like before you added the $80.00 of chemicals that they recommended.

hit it and hit it hard!



LifeTime Supporter
Apr 22, 2007
My goodness that's an awfully high CYA for a new pool. It should be about half that unless you have a salt chlorinator.

You need to add enough bleach to bring it to shock level of at least 25 ppm and keep it at 25 ppm day and night (adding bleach throughout the day). Keep it at 25 ppm until it holds within 1 ppm overnight.

You should bring your pH down.

Consider dumping about half your water to get that CYA down to at least a somewhat tolerable level - it will still be high, though. You'll probably find it a lot cheaper in the longrun in money and time.

Don't use anything but liquid chlorine, so you don't bring it back up again.

While you are getting it back in balance, run your pump 24/7 and backwash when necessary.


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
You really need to get your PH down right away. Particuarly since it could well be even higher than 8.4, since many of the tests will show numbers higher tha 8.4 as 8.4. Also, chlorine is not effective at high PH, so adding chlorine won't help much until the PH is brought down. I would aim for 7.2 to 7.4.

With CYA around 150 you need to maintain FC above 12 and shock to 30 or more. To kill the algae you will need to shock the pool. That means bringing FC up to at least 30 and holding it there until you have no chlorine loss overnight. This must be done agressively, testing and adding chlorine at least three times a day to maintain 30 or higher.

I really don't recommend having CYA above 90 and somewhat lower than that is even better. You should reduce it by replacing water. The simplest way to do this is to add water continuously while draining water out to keep the water level more or less uniform. If you have an overflow drain all you need to do is add water, otherwise you will need to pump some water out while you add water.

Keep in mind that pucks and most powdered chlorine add even more CYA. And you don't want to add more calcium at this point, so cal-hypo isn't the best idea either. I would suggest using bleach to shock the pool. Otherwise your CYA levels are going to go even higher and cause more problems.