Water chemistry optimization for stock tank noob

[BobStrauss]

So I’m a TFP noob with a 7.5’ round stock tank (~620 gallons) in Central Texas. Using an Intex 1500 gph cartridge filter, and the water in our area is pretty dang hard.

I have the TF-100 kit, and after a few days filled now I got the following readings this morning:

FC: 1.0
CC: 0.5
pH: 7.7
TA: 210
CH: 650
CYA: 30

This afternoon I added chlorine (10% bleach from Walmart) according to the app’s recommendation, as well as dry acid (Clorox brand) to lower pH to around 7.2. I’m trying to acidify and aerate (with pump) in order to get TA down.

Two questions I’ve got though:

1) I’m assuming I should ditch the dry acid and use muriatic acid instead? Seems that sulfates are a problem over time, and I’m my area I’m guessing I’ll always be fighting alkalinity?

2) Once my TA is in check, would borates be a worthwhile next step? Maybe boric acid granules so I don’t have to fight the TA battle all over again?

3) Is there any need to shock the pool? The water seems really, really clear - no algae or anything it seems.

Thanks for the help!

 

[mknauss]

1. Correct.
2. I am not sure how big a deal scale is to you. That is the only reason to drive the TA lower. Otherwise just keep pH in the 7's.
3. No. But beware that letting FC fall below minimum at any time could result in algae.

 

[JoyfulNoise]

Do you have a cover for it? Covering it when not in use can help keep the chlorine UV loss down. Using a solar blanket and a cover together will help lower evaporation loss too.

Stock tanks are going to be more like hot tubs than pools. You should follow the chemical process for that.

 

[BobStrauss]

Checked again this morning before correcting:

FC 1.5
CC 0.5

Should I start erring on the high side since it drops so low every day? The app calculates a correction to 4 ppm, but would it be better to aim for 5 or 6 instead?

Regarding a cover, would using one increase temperature in the pool? This is another issue I need to sort out: while it stays nice (mid-upper 80s in the morning), it gets to feeling like warm bath water in the afternoon.

 

[Oly]

Yes keep your FC on the high side of your target zone FC/CYA Levels and check after adding to confirm. Rising water temp will be an issue for your above ground and shallow tank. A cover will raise temp but save you some FC loss. Consider putting up shade over your tank.

 

[BobStrauss]

Since I’m in central Texas, which is oppressively hot, would it be a good idea raising CYA to 50-60, and then FC according to the chart you posted?

I’ll look into some kind of shade, but ideally I would like to lower temps some other way - fountain return perhaps?

Thanks again for the advice!

 

[Oly]

Raising CYA will reduce your daily FC loss slightly and you will need to keep your FC levels in the new target zone. Testing daily now will determine your daily FC loss. Add enough FC to cover your expected loss and ensure you do not drop below the minimum. Best to remain in the target zone and also be sure to anticipate higher demand like a full moon party with all your neighbors.

 

[JoyfulNoise]

A fountain cooler would work but you might lose a lot of water to the spray. Throw a nice block of ice in it just before you want to use it … it’ll be refreshing

 

[BobStrauss]

Now I’m wondering if I need to shock the pool? Yesterday I added chlorine to up the number to 5.5 (had measured 1 FC and 0.5 CC), but this morning it had already plunged to 0.5 FC and 1.0 CC. I’m also noticing an oily film on the surface that won’t go away, even with excess pump runtimes and use of scum balls.

Any recommendations on how to tackle this? I just added CYA to get up to 50 ppm, but perhaps that was a mistake? I should I be shocking now instead?

 

[Msch99]

With a cya of 50 your new target is 6-8 ppm FC. Anything below 4 is an invitation for algae. I would shoot for 8 and allow to lower if no issues…which you may already have.
You should perform an OCLT. Overnight chlorine loss test to check for algae. Guessing you won’t pass and will be in slam mode tomorrow which is 20ppm. See pool school for OCLT and slam instructions.

 

[YippeeSkippy]

Anyone wearing body lotions? Lots of hair products or tanning products?? Those get oily..... chlorine will help break them down in time.

I'm curious how you got such high calcium? Not just hard water but super high?? You could get a small Salt Water Chlorine Generator, y'know?

Maddie

 

[BobStrauss]

Regarding lotions: oh yeah, my wife slathers herself and my son in tons of sunscreen before going outside. I put on bug spray myself, so that might add to it.

Not sure regarding the calcium, I just assume it’s normal for our area (San Antonio) since we basically live on limestone. The water that got that measurement came out of the garden hose less than a week ago.

I added some Spa Stain & Scale remover I picked up at Leslie’s, as I heard that had helped someone else with a similar problem (Houston stock tank pool). But I also swapped out my filter this afternoon, the previous one was absolutely filthy, and since then it’s cleared up 90+%. Guess I can’t be totally sure whether it was the additive or the filter, but I’m guessing the latter.

I’ve corrected my chlorine to CYA now and will do the OCLT tonight. Will start the SLAM process tomorrow if needed. Thanks, yall!

 

[TexEdmond]

I’m also noticing an oily film on the surface that won’t go away, even with excess pump runtimes and use of scum balls.

tons of sunscreen

I recall a thread a few weeks ago where a user was posting on their smaller capacity pool being completely gunked up after heavy bather loads and they were experiencing devastating chlorine loss on an extended SLAM. It clogged up their filter and then they were doing TSP soaks and rinsing out their filters too. If you're doing a stock tank pool, is it possible you're rural enough to be on well water? I think that user ended up just having to drain and refill. 650 gallons is nuuuuthin unless you've got really expensive municipal water.

Good to hear your filter swap helped things. There's a bunch of good resources here for soaking / spraying / rinsing / acid washing to keep them fresh.