FAC will not hold

[BSmith]

My pool is 25,000 g. My most recent reads (from yesterday) are as follows:

• FAC 3
• TAC 3
• CH 210
• CYA 100 (High)
• TA 110
• pH 7.4
• Phosphates 1000 (High)

Today my FAC is 0. I cannot get the free chlorine to stick.
2-3 weeks ago, when I realized CYA was high, I stopped using tabs and chlorbrite - now using bleach, and a lot of it!
I've attacked the high phosphates with PhosFree, with no change in the reading.
One last thing, I have not changed out the sand in my filter in 7 years - probably an issue!
Pool is crystal clear, I'm just having to put a lot of bleach to it.
Any suggestions? Thanks.

 

[Texas Splash]

Hello and welcome! You have a few things to contend with, so I'll get this thread started with the following:
- Sand rarely needs to be replaced unless something was added to it to make it unserviceable. Backwashing, rinsing, etc are generally good
- How did you test and get those readings? TF-100 or Taylor K-2006?
- CYA at 100 could actually be higher depending upon how it was tested; requires a partial drain/refill to lower before doing anything else
- Your FC is extremely low if your CYA is indeed 100; I suspect you have organics thriving in the water.
- Phosphates - don't bother with it. It's just money for the pool store. Sanitize/maintain your water properly and you won't have algae around to eat phosphates.

If FC is dropping, it's either from the sun and/or algae - even if you don't actually see "the green" yet. Once you confirm the testing method and CYA (or adjust CYA), I suspect you are a good candidate for a "SLAM" via Pool School - SLAM - Shock Level And Maintain. Once you reply with some answers to the questions above we can hopefully get you going. Welcome to TFP!

 

[BSmith]

Thanks for the quick response. The test was done at Leslie's - not sure what method they are using. Surprisingly, the individual that conducted the test wasn't that concerned with the CYA of 100 - so I'm thinking if it was higher than that, her results would have shown it.

 

[ScottCh]

Surprisingly, the individual that conducted the test wasn't that concerned with the CYA of 100

That is because they either ...
A) don't know the relationship between CH and CYA
or
B) don't care because it affords them the opportunity to sale you more miracle cures.

so I'm thinking if it was higher than that, her results would have shown it.

I'm fairly sure most, if not all, methods of normal testing top out at 100. I doubt they took the time to do a 50-50 diluted test for you.

 

[JVTrain]

I'm sure they weren't concerned with the CYA being that high. Pool stores know nothing about the relationship between CYA and FC and certainly don't teach their employees about it.

Methods here at TFP are not compatible with pool store advice or testing. A proper home test kit to test your chemistry levels yourself at home is required. Pool store testing is generally inaccurate and solely there to get you in the store and sell you products you may not need. You can see the recommended test kits here: Pool School - Test Kits Compared

Sand usually does not need to be changed unless it was severely neglected and just easier to change the sand than perform a deep clean/dechanneling of the filter.

High FC demand with high CYA levels means there is likely something growing in your pool. Without a test kit, you cannot accurately determine how much FC you're losing each day.

The Pool School articles here are a very valuable resource, check out the one Pat mentioned as well as ABCs of Pool Water Chemistry to get started.

 

[lefty51]

Hello there BSmith from shocker country, and welcome to TFP.

As you will soon learn, we put NO faith in pool store testing. First suggestion is to get a good test kit (I prefer the TF100) and do your own testing. That way you always know what's in your water.
As TS stated you might need to SLAM, but you need to get the CYA down (if it truly is that high) as it will take a whole lot more bleach to conduct a SLAM.

I would suggest doing some reading in POOL SCHOOL to get the hang of slamming and doing your own testing. Others will be along to explain how to add your pool particulars to your signature and expand on the things you need to do to get going the TFP way.

Again welcome and ask all the questions you have, we are here to help

 

[Texas Splash]

Yeah, that's a VERY common theme for all of us who were at the mercy of pool store testing at one time. Don't get me wrong, there are some good people out there, but there just too many who were poorly trained, have a strict selling agenda to follow, or simply don't care. Not to mention CYA testing is best suited in natural sunlight for best results. If you order a TF-100 or Taylor K-2006C, you'll be on the road to recovery. Both kits use Taylor reagents. It's just that you get more for your money with the TF-100. You can order them here and see a comparison of kits on the next link as well:
TFTestkits.net
Pool School - Test Kits Compared
Don't forget to ask for the speed stir! Great tool.