Can't keep chlorine levels up - need another set of eyes!

[CPS Reno]

This isn't my pool, it's a customers. Trying to troubleshoot a pool chem problem on someone else's pool isn't always easy. Sorry to disappoint everyone too, but we aren't your typical "pool store". I firmly DO NOT believe in the many snake oils out there.........even to the point of agreeing with the TFP method almost always. That's why I'm here, sometimes you can stare at a problem too long and need someone to tell you the obvious.

Pool is 3 year old, fiberglass with sand filter and SWG. I know there are many kids and even dogs in the pool often, but the issue is much worse this year and any of the others. Pool is normally clear and was clear when we got the results below. The only issue is the chlorine level doesn't want to stay any higher than 2 or so.

FC

 

[tim5055]

The first question we always ask is for a full set of test results from a reliable source.

FC
CC
pH
TA
CYA
CH

What is the pools normal source of chlorine? I see a SWG, but is it being used? If so, how old is it?

Is the pool "shocked" regularly? If so, with what.

What test kit is being used?

 

[CPS Reno]

I'll start off with an apology that I'm not the usual "pool store" that you think so highly of. I firmly believe in SOLID water chemistry principles and agree with 99% of the advice given here. Most of the snake oil out there is just that and we don't sell it. Having said that, helping pool owners with their own issues isn't always easy. Either way, I've been helping someone with their pool and I'm pretty certain I know what the problem is, but having a hard time using logic to find the solution.

Pool is a 3 year old fiberglass pool, 15K gallons with salt system and sand filter running 24/7. Can't keep chlorine levels where they should be. Water is almost always clear though. Not the clear that I think it should be, but it's not what I would call crystal clear like my pool is. Please give me your input on both what you think is wrong AND what I can do to convince the customer the right steps are. At this point, the blame is 100% on the salt system not generating enough chlorine. Part of why, is that this problem hasn't been there the last two seasons. I know there's a lot of kids in the pool and dogs periodically. Anyway, here's the info:

These numbers are averages of the last three "random" samples we've received,. We use both the Spinlab and confirm with K-2005 Taylor kit, along with Taylor phosphate, iron, copper, etc kits.

FC 1.7 to 2
CC .15 to .2
pH 7.9 to 8.1
CH 285
Alk right around 100
Cya 25 to 35
No iron or copper
Phosphates about 200-300

The winter here really affects ALL out of the hose and it's hard to keep it semi low. Again, as a pool store you run kind of blind when relying on the customer to complete the entire SLAM as directed. OCLT is HIGH (it's varied, but usually over 5PPM lost) and SLAM has been done twice. Last samples that we actually got before/during SLAM showed me the chlorine level was about 15 for about 10 days. There's a point where you "think" the customer isn't doing what's needed and you have to start getting direct about what needs to be done, but having data to show that isn't always easy to show either.

What do you think?

 

[Msch99]

Not an expert, but at first glance my concern would be FC level to CYA level.
1.7 FC for extended periods with CYA potentially in high 30's to 40's is leaving an opening for algae. Doesn't match up to Chlorine/CYA chart very well.
I would count CYA as 40, shoot for FC in 5-7 range, never below 3 and see what happens.

 

[CPS Reno]

Agreed, that's what I've been trying to get her to do for a couple months now. I can give her 5# of cal hypo and the water will come back 3 days later with FC less than 2.

 

[Msch99]

Curious as to why calhypo instead of chlorine?

 

[CPS Reno]

More of a preference than anything. Also, our pools almost always need calcium and we know how to manage any pH changes that sometimes seem to come from cal hypo.

 

[Msch99]

More of a preference than anything. Also, our pools almost always need calcium and we know how to manage any pH changes that sometimes seem to come from cal hypo.

FYI. I wasn’t 2nd guessing your choice, just wanting to learn a bit.

 

[tim5055]

Your next step is an overnight chlorine loss test to eliminate organics

Perform the Overnight FC Loss Test (OCLT)

The Overnight Chlorine Loss Test tells if the SLAM is finished or if you need to start a SLAM. This article says how to do the OCLT.

www.troublefreepool.com

I‘m not a fan of the spin lab as I’ve personally seen horrible testing from them.

 

[YippeeSkippy]

Any pool with a lot of kids in it, and an occasional dog is probably subject to a lot of pee. Owner needs to take on task of accurate FAS-DPD testing daily to monitor and augment the chlorine immediately when needed....not two days later.

Is SWG undersized? Is CYA too low to protect chlorine?

Maddie

 

[CPS Reno]

Thanks for the replies and help. I agree on the spin lab, we constantly confirm readings with our Taylor but it actually helps us to have both results. Since this is a pool we built, we have 5 other same model pools with same SWG that don't have an issue. But, the long answer is yes it's technically undersized. Most people don't want to pay the extra $750 for the "oversized" SWG, even though it's normally about a 1% upgrade cost when compared to total project costs. It's the game we are forced to play sometimes. We keep our customers CYA between 20-30 for most pools, as it's my opinion/experience that low chlorine levels work better at that spot. We even print the CYA/Chlorine chart from TFP on our spinlab test results, just so customers can see the affect they have on each other.

I guess I need to stick to my gut and just tell her that she needs to follow SLAM to a tee or else she'll have issue the entire season. I will report good results on water clarity using enzymes on this pool (and others with high bather/kid/dog load) for clarity though. More of a side note.