Can’t hold chlorine

[JoelsPoolHouston]

We cannot hold chlorine in our 2-month old pool. We will boost the chlorine content up with stabilized dy-chlor (or shock, if the free chlorine doesn’t match), but over the course of a couple days, both the total and free chlorine will gradually decline to zero.

Our chlorinator (set on the highest setting of “5”) goes through about 1 tablet per week (I keep it full, and add a tablet if there is room). I hear others say they hold the chlorine level by adjusting that chlorinator setting….but even wide open, we don’t seem to get enough chlorine input.

I don’t think this is a total vs free chlorine problem, as we have good luck shocking the pool when those two separate (e.g. after we have a bunch of kids swimming), and total/free chlorine come back to equal (and then will decline together over the next couple days).

What do you think might be our problem? Or what would you recommend trying??


Recent chemistry (from Leslie’s)
pH 7.6
Alk 104
CyA 31
FAC 1.0
TAC 1.0
CH 380
TDS 800
Pho 242
FE 0
CU 0

Pool/equipment
In-ground, concrete pool + hot tub
18,000 gallons
Filter vessel
Chlorinator: Pentair 320 automatic in-line chlorine/bromine feeder
Ozone system
Pump 10 hours/day x 3200 RPM

Chemicals
Shock: Leslie’s Power Powder Plus 73
Chlorinator: Regal Chlorinated Tablets 3” (Trichloro-s-triazinetrione)
Chlorine granules: Regal Dy-chlor II (Sodium dichloro-s-triazinetrione dihydrate)
Acid: Muriatic Acid 20 Baume Hydrochloric Acid 31.45%

 

[ajw22]

Welcome to TFP.

We have different methods of pool care then the pool store. Review...

Pool Care Basics Archives

Your one-stop shop for all things TFP to include: ABCs of Water Chemistry, Recommended Chemicals/Levels, Test Kits, Troubleshooting, and much more!

www.troublefreepool.com

To follow our methods you need to do your own testing with the Taylor K-2006C test kit or TF100 Test Kits

I suspect you have algae in your water that is consuming your chlorine. Once you have your test kit post your test results and do a Overnight Chlorine Loss Test

If you have algae then you follow the SLAM Process

 

[crusemm]

Something to note, you can have algae in a pool with clearish water. That means you are in the very early stages of the algae bloom. If you can get ahead of it here you can beat it pretty easily. You do need to do your own testing though, as pool store numbers are notoriously unreliable.

 

[JoelsPoolHouston]

Sure enough, we are losing excessive chlorine overnight (basis the Overnight Chlorine Test), and have discovered some hidden algae patches......so getting ready to perform the SLAM process. Will share the update on how that progresses. Appreciate the help so far!

 

[IceShadow]

Sure enough, we are losing excessive chlorine overnight (basis the Overnight Chlorine Test), and have discovered some hidden algae patches......so getting ready to perform the SLAM process. Will share the update on how that progresses. Appreciate the help so far!

Did you end up getting one of the recommended test kits (dropper-style, FAS-DPD)? Without that it's pretty much impossible to follow the SLAM process. Can you fill out your signature with your pool and test kit info? You can see mine to use as a template. If you're on a mobile device, turn it sideways to see signatures. The link to change your signature is here: https://www.troublefreepool.com/account/signature

 

[JoelsPoolHouston]

You guys were right on....seems likely our problem was algae. Running the SLAM for couple days (and doing a first cleaning of our filter elements) has dramatically lowered our chlorine load, with overnight chlorine loss now < 1 ppm. The FAS-DPD test indeed gives a real number to work with (would have been much less accurate/difficult to monitor with test strips). Also trying the shift over to bleach for chlorine. I appreciate the help!

 

[Oly]

A couple good short vids....