First Chemistry Test Results

[AquaNouveau]

Good afternoon! For background, I recently purchased a house with an existing in-ground pool. In my last post a couple weeks ago, you guys helped me understand and operate all the pool equipment. My TF-100 test kit just came in and I ran through the battery of tests. Here are the results:

No visual problems with the water, it looks great.
pH > 8.2
FC = 1.5 ppm
CC = 0 ppm
CH = 650 ppm
TA = 180
CYA = 80-90 ppm, probably closer to 90
Temp is cold, probably 45-50.

It looks like the real concern is that the CYA is well above the recommended range and there is no good way to lower it without draining and replacing some of the water. Everything else will need to be re-tested and balanced after that point anyway. I don't relish the idea of draining and re-filling. Is it possible or advisable to limp along with a CYA of 90? My understanding is that I'd have to maintain a pretty high FC. Any tips on draining are welcome too.

 

[mknauss]

You can live with the high CYA if you like. It makes it extremely important to maintain your FC in the target range for the CYA. That level makes the pH testing more difficult as once your FC reaches 10 ppm, it begins to effect your pH test results.
FC/CYA Levels
Recommended Levels

Take control of your pH and lower your TA now so when the water warms you are not in the range of creating scale.
By chance, do you have a whole house water softener? If so, consider filling the pool with soft water when evaporation really kicks in.

 

[AquaNouveau]

No water softener, but I think it is on the list of home improvements for other reasons as well. I'll keep that it mind when it comes time to begin refilling in earnest (have been topping off 1/2" a week or so).

 

[mknauss]

That is about right for evaporation right now. It will increase to 3/4" or a bit higher each day once May arrives.

 

[Rancho Cost-a-Lotta]

You could more easily manage a CYA of 90 with a SWG. SWG minimum FC would be 4 ppm and target would be 6 ppm. Any plans on installing one?

Keep an eye on your CSI. You're well on the positive side of 0.0. Adjusting pH is the best way control CSI.

You need to get some chlorine in the pool ( to get to a minimum of 7 ppm). Target 10 ppm.

Best of luck!

 

[AquaNouveau]

SWG would be great, it's on the list, along with updating to a variable speed pump, but unfortunately our furnace started leaking carbon monoxide and will need to be replaced, so major equipment updates for the pool have been postponed.

I'll go liquid chlorine and muriatic acid hunting tomorrow to get the FC where it needs to be and start working on the pH and TA.

mknauss mentioned (and I've read in 'Pool School' as well) that pH readings start to get unreliable around 10 ppm FC. Is there an advisable way to address this? My foggy memories of Chemistry 101 are that ph is a log scale, so simple dilution ratios won't work, but I'm guess there's some math that'll get me where I need to be.

Anyway, first things first, chlorine and acid will go in the water tomorrow.

 

[mknauss]

Is there an advisable way to address this?

Test the pH at or below a FC of 10 ppm. When you do the pH test, read the result quickly. It takes some time for the color to change when at an elevated FC.

 

[AquaNouveau]

Test the pH at or below a FC of 10 ppm. When you do the pH test, read the result quickly. It takes some time for the color to change when at an elevated FC.

Good advice, thanks!

128 oz of 14.5% muriatic acid just went in the pool with the pump running, I'll take a pH reading tonight. I imagine it disperses pretty quickly, but some sources online said to give it a few hours to stabilize before re-testing, so I'll do that. That amount was recommended by the PoolMath app to hit between 7.1 and 7.2 (and is the amount in a gallon jug!). I'm aiming on the low end of the recommendation with the assumption that my high TA will bring it back up over time and lower the TA into the range I want. There's no real aeration action, so it may take awhile, but I don't get the impression it's urgent yet.

I've also got some 10% chlorine. Once I get a good reading on pH, it'll go in as well. Conveniently, PoolMath reports that 115 oz is required to get to a target of 10 ppm FC, so I think I'll just pour a jug of that as well, rather than trying to reserve 13 ounces. The biggest risk in over-chlorinating just seems to be the waste of money, and I can live with 50 extra cents going in the pool for now.

 

[Rancho Cost-a-Lotta]

Sounds like you got it all figured out. Good job!

You may try to find a local independent pool store that sells HASA products in refillable containers. The chlorine is 12% and MA is 31.45%. It's a better value for me than HD, Lowes, or Wal-Mart.

 

[Newdude]

Also, rerun that CYA test after warming the water up to room temp. The CYA test doesn't like cold water and the overly subjective test is hard enough to call on a good day.

 

[AquaNouveau]

Did a partial re-test to see what the effects were after 24 hours.

pH = 7.5
FC = 11 ppm
CC = 0 ppm
TA = 150-160
CYA = 80-90 still... maybe closer to 80 this time?

pH was 7.2 a few hours after acid addition and has crept up to 7.5, which makes sense with the TA coming down I think. I'm a little surprised the FC is so high, although I'm not complaining. I was expecting it to be around 10 after adding chlorine and then lose at least a little today, but it seems to be happy. We'll see what happens in another 24 hours there. CC staying zero is a positive sign that I'm not growing something somewhere.

Still getting the hang of the CYA test. I appreciate the advice to try it with room temperature water... unfortunately we are without central heating until next Monday, so "room temperature" is a loaded term right now. I'll keep monitoring (or more accurately, practicing the test).

Overall, it seems like things are in decent shape and the numbers are moving the way they are expected to. I expect everything will start moving faster once the weather starts to warm up and we get more sun, but I'm happy for now.

 

[Rancho Cost-a-Lotta]

FC loss this time of year is minimal. In our area, you'll go from losing less than .5 ppm daily during the off season to 3-4 ppm during peak swim months. High CYA will work in your favor when things start heating up.

You'll have to keep an eye on calcium hardness. I'm not sure what your fill water is like, but testing TA and CH levels of your fill water will give you an idea of what you're up against.

 

[AquaNouveau]

I did a CH test of the fill water and it was about 350, so not exactly soft. I didn't think to do a TA test, I'll do that next time I bust out my "chemistry set".

 

[Rancho Cost-a-Lotta]

A result of 350 CH is super high. When you have a chance, retest. Take your time between drops to swirl the vial. Hold the reagent vertical and squeeze just enough to allow the drops to fall off the tip. A Speedstir or Smart Stir really helps to get accurate and consistent test results (especially on the CH test). If you get the same results, best to head Marty's advice about a softened fill water when your able to do so.

 

[mknauss]

I did a CH test of the fill water and it was about 350

I would think Palmdale would get their water either from the Owens Lake or Colorado River. Neither are that high in CH. So do test your fill water again. However, if you have a water softener, it will be wise to use that to fill your pool due to evaporation.

 

[AquaNouveau]

Will do, thanks for the gut check on the numbers.