I just can't get the green to stay away

[Davek1999]

So, just tested my pool about 3 days ago to get the information below

FC = 2.5
CC = 0
Calcium = 300
TA = 16
CYA = 50

It is a salt water pool and is quite large at around 42,000 gallons. We just can't seem to keep the green to stay away. When we got frustrated and went to a pool supply store they sold us 16 gallons of liquid chlorine, and this worked for about a week and a half. I tested and got the numbers above and now it is green again. We have had this issue every year and are pulling our hair out trying to figure out how to best treat the issue so it doesn't come back. Do we need to add liquid or powder chlorine to the pool on a more regular basis to avoid this? Is there a piece of equipment that might not be working and we are just masking with the addition of chlorine? Ready to just quit

Any help would be greatly appreciated.

 

[mknauss]

Is your TA really 16? Hard to test that.

Your SWCG is undersized for your pool. You need to run it 24 hours per day during the summer, and still add liquid chlorine most likely, especially on high bather load days.

You should also consider holding your CYA in the 70 to 80 range. But not until you SLAM this pool to eliminate the algae. Pool School - SLAM - Shock Level And Maintain

Be sure to check your pH before you SLAM and get it to 7.2.

Take care.

 

[YippeeSkippy]

Well, I immediately noticed that your FC is far too low for a CYA of 50ppm. Also your SWG is too small for such a large pool. So even running 100%/24 hours a day you probably need to augment your chlorine needs with bleach.

How often are you testing your water when you *don't* have problems? Not testing could be one reason you keep getting algae. If you test almost daily your first sign of problems might be caught early and dealt with before a full fledged outbreak occurs.

What is your pH? Did you mean to type that your TA is 160?

Please review this to see how much FC your CYA requires- [FC/CYA][/FC/CYA]

And it sounds like you need to perform a complete SLAM procedure. Do you need to order refills of your FAS-DPD FC/CC test powder or reagent liquid now so you don't run out during the SLAM?
Directions for SLAM--> SLAM Process

Let us know how we can help you if you have questions about the SLAM.

Maddie

 

[Griswald]

With CYA at 50, the minimum FC you should ever have is 4. No wonder you have algae, a low chlorine value will allow algae to grow.

 

[Swampwoman]

OOPs, cross posted...am a slow 1 finger types on iPad

Hi Neighbor, and welcome to TFP.

We can help get you sorted, but first, I gotta say that your T15 is going to have a hard time keeping up in your size pool. I know its rated for 40k but at TFP, we advocate doubling the rating where possible. (Eg I have a T15 on my 24k gallon pool.)

Here's why - mfg ratings assume output at 100 percent over 24 hours. So in MY pool, that output nets me a "possible" 7.9 ppm of FC a day...meaning in my case I run it 12 hours at 50% to make up for about 2 ppm use of FC per day.

In your pool, you'd have to run it 24/7 at 100% to net 4.5 ppm max a day in a 40,000 gallon pool. While most pools will use 2-4 ppm a day, it only takes a bit of extra chlorine consumption (a party, low cya that allows more FC to burn off on hot sunny days) for a SWG to fall behind in your conditions.

Since you already have the swg installed, once you're truly cleared (see slam link below) the pool and ensured your CYA is 70-80, you could continue operation and just give it a boost once a week or so with some liquid bleach/chlorine to help it stay ahead.

When the cell has tapped out its lifespan, you might consider switching to a brand rated for a 60k gallon pool. Or see if its viable to add a second T15 (I've seen this n commercial applications but am unclear what's involved.)

Now, for what to do to get clear....I'm going to post three links to share the TFP method.

First, if you don't already have one, you will need specifically a FAS/DPD test kit, either the TFT100 (better value) OR the Taylor K2006 available at TFTestkits.net

That's because all TFP methods are based on the [fc/cya][/FC/cya] ratio -- see the link and look at the swg rec level.

The goal is to maintain sanitary water conditions using this science-based ratio of stabilizer and chlorine.

To clear your water in order to be able to rely, more or less, on the swg and keep green away, you will need to perform a SLAM Process - please read. You will see why you need the FAS/DPD test kit.

If you go through this process, even with the underpowered swg, I believe you will truly be able to call your pool "trouble free"

Reach out with questions etc. and we'll help you through the learning curve

Cheers to clear!

 

[Davek1999]

mknauss - You are correct, just tested again, it's 160, forgot to X 10 :???:

I have read through and followed the slam process and it has worked great in the past. Knowing now about the SWG, that makes sense why we keep running into this issue over and over again. Can you guys recommend an option for an efficient larger unit?

 

[Swampwoman]

Circupool RJ60 puts out 3 lbs of chlorine gas a day versus the 1.45 lbs the T15. Autopilot has a unit that puts out 2 lbs a day.

But you'd have to change the whole system, not just the cell.

Here's a Hayward blog about "commercial" size (40k and up) solutions...they have a commercial unit tat produces 6 lbs a day
It addresses why chained residential units aren't ideal as a solution.
Salt Chlorine Pools for Commercial Pools and Spas