CYA level too high

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Darren44

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Sep 4, 2013
5
Hello,

I live in Spain and have an in ground tiled pool of 30,000 gallons. I have been looking at the forum for some time since I started having problems with algae and cloudiness. Have been using three effect granules between January and June and occasionally adding some acid to keep the PH down. I have a Guardex 4 in 1 test kit and the levels were all fine. All was good until I left the pool with some guests in the house for a couple of weeks.

They let the water level and Chlorine level get too low and so the pump wasn`t filtering properly and we had a green pool on my return. Started to put a lot of Chlorine tablets in the skimmer to get the Chlorine up and added some flocculant. things have improved but the water is still a bit green and not clear.

From the information on the forum I suspected that the CYA level was too high but could not test it. In order not to raise the CYA level by using the tablets started to add bleach to get the Chlorine level up to 3. Haven`t been able to shock as the have had a lot of kids staying who want to go in the pool every day. Have ben adding at least a gallon of bleach a day but the level is hard to keep up. Just got the water tested at the pool store with the following readings.

PH - 7.7
FC - 2
TAC - 1.5 (I think)
TAB - 3.4
Total Alkalinity - 80 ppm
CYA - 88

I think I need to lower the CYA and shock the pool which I can now do. Could you advise me please the best course of action.

Best regards,

Darren
 
Welcome to TFP! :wave:

You are correct that the CYA is a bit high and the FC is way too low for that CYA level (see Chlorine CYA Chart). The only way to lower CYA is to do a partial drain & refill. In your case, you are looking at draining & refilling about 50% of your pool water.

Darren44 said:
Started to put a lot of Chlorine tablets in the skimmer to get the Chlorine up and added some flocculant.
Click to expand...
The tablets contain CYA as part of their formula, so I would stop using those in favor of plain unscented liquid bleach. Also, the flocculant is unnecessary.

After you do the partial drain & refill, you will need to perform The SLAM Process. My biggest concern is, are you able to get a good test kit of your own that is similar to one of these: Recommended Test Kits? If not, can you get the FAS-DPD Chlorine Test? During the SLAM process, you will need to test chlorine at least a couple of times a day.

Darren44 said:
In order not to raise the CYA level by using the tablets started to add bleach to get the Chlorine level up to 3.
Click to expand...
An FC level of 3 ppm is not even close to what you need to get rid of the algae. Let's assume you get the CYA level down to 40 ppm after the drain & refill. At that CYA level, you would need to maintain a target FC level of 16 ppm during the SLAM process until you pass the criteria listed in the SLAM article. If CYA was reduced to 50 ppm, you would need to maintain a target FC level of 20 ppm during the SLAM.
 
Hi,

Many thanks for such a fast response. Stopped using tablets three weeks ago. Water is pretty expensive over here but if a partial drain is necessary that is what I will have to do. Doesn't seem possible to get those test kits in Spain but will keep trying. What should I do in the meantime?
 
I would do the partial drain & refill as soon as possible. At the current CYA level, the amount of chlorine needed for both the SLAM process and for ongoing maintenance will be difficult to maintain.

  1. I would also try to get the best available test kit you can get locally. In order to properly do the SLAM process, you will need to test FC at least twice a day. [/*:m:2unwop80]
  2. I would also familiarize yourself with the Pool Calculator (see link in my signature below). This will help you determine the right dosages for FC and other chemicals.[/*:m:2unwop80]
  3. Stock up on plain unscented liquid bleach. You will use a lot of it during the SLAM process.[/*:m:2unwop80]
 
For the slam process, you will need to know FC levels above 10. Any way to get a "FAS-DPD chlorine test" (not the same thing as the DPD chlorine test in the linked kit).
 
Hi,

Think I have found a shipper for the Taylor kit and will forward the link for any interested members. In the meantime I have drained only 15% and started slamming. With my kit I can't really measure more than 5 for FAC but just started adding bleach as per (roughly) the pool calculator.

Just had to do something. Have been adding 40 litres of 5% bleach for two days, then 30 for 3 days, then 20 for two days. By using 50% plain water in the test kit I would say the chlorine level has not dropped below 10 on the DPD test.

Results were not good at first but there has been a steady improvement and now the water is blue and slightly grey. Almost clear. I am encouraged but the PH test is doing strange things as you suggested. Starts off showing 7.2/4 but darkens to 8+.

I know you won't approve of my methods but what do you think about the PH?

Sorry for such a long post
 
Disregard your pH since you have started to SLAM (sort of). It will not read correctly. Concentrate on your FC.

"doing something" is fine if it's working for you. It is hard for us to give any advice since your numbers are likely unreliable and we are thousands of miles away and can only rely on numbers that you post for us.

Stabbing in the dark at imprecise numbers is hard because our methods involve the precision you need with an FAS/DPD test kit.
 
Thanks Dave,

I am amazed how fast you guys respond. I am getting the Taylor kit and will supply precise numbers in future.

From what I said do you think I have at least
succeeded in killing all the algae for now?
 

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