Initial Water Chemistry

RS220

Gold Supporter
May 24, 2019
46
Fresno, CA
So I opened up my TF-100 test kit this weekend, and ran a complete set of tests on our tap water to get an idea of what we will be facing in a few weeks when it’s time to fill, and also because it's fun.

Results are below, along with what I think our suggested actions and things to watch will be. I’ve read through Pool School and all the water chemistry portions of the site, I’m now just trying to apply it to what we have. Please help explain where my thinking or priorities are wrong.

The pool builder is estimating 25K gallons for our pool. I don’t know yet if we can actually read our water meter for a better idea of true volume, as it is under a driveway access panel.

I’m using the recommended levels from Pool School, with the understanding that we shouldn’t turn the SWG on for the first 30 days to prevent plaster dust from mucking it all up. So I believe I use the “with Bleach” column for the initial opening, then switch to the “with SWG” values once it’s up and running. Please correct me if I’m wrong, or there’s a different approach to take.

with Bleach
FC 3-7 (See chart)
pH 7.2-7.8
TA 70-90+
CH 250-350
CYA 30-50
with SWG
FC 3-5 (See chart)
pH 7.2-7.8
TA 60-80
CH 350-450
CYA 70-80

pm.JPG



FC – 0 / Acceptable Range 3 – 5 (3 - 7 without SWG on), will target 5 for initial opening.
Free chlorine is zero, which is what I expected and makes sense. Seems like I can just use 5 as a target both pre and post SWG.

Based on this, it sounds like the initial pour of liquid chlorine assuming 6% bleach is ~260 ounces, or a little over two jugs, but that seems like very little. I got the number from Pool Math.

pH – 7.8 / Acceptable Range 7.2 – 7.8, not sure what to target for initial opening, maybe 7.5 to leave a cushion for it to drift up?
Seems high. And I believe as the Pebblefina cures, it will continue to drive this up. So, looks like we’ll need to invest in some muriatic acid for sure.

Since it is still within the acceptable range, should I try to adjust this down to begin with, or wait for it to really climb? If lowering, sounds like I should need 43 ounces of 31.45% muriatic acid.

TA – 190 / Acceptable Range 60 – 80 (70 – 90+ before SWG is turned on), not sure what to target for initial opening.
Also seems high! I believe combined with my high pH it is a greater problem. Pool school says only to do this do lower pH and/or CH, so I’m a little confused about when I need to worry about this since one is high and the other is low. I’m also not sure about which range of numbers I should target for the initial opening vs when we turn the SWG on. Aerating to lower TA will raise my pH even more, so this one just seems like a trap. I definitely need some feedback on when/if to address this.

CH – 175 / Acceptable Range 350 – 450 (250 – 350 before SWG is on), not sure what to target for initial opening.
Lower than I expected. We typically have hard water in the area, but being part of a private water district ours is much lower than surrounding areas, but I still expected this to be higher. Looks like I might actually need to increase this.

I believe that as the plaster cures and is brushed this will continue to increase. Do I need to raise it initially, or wait for a while for things to settle in before adjusting this?

CYA – 0 / Acceptable Range 70 – 80 (30 – 50 before SWG is turned on) will target 40 for initial opening, then raise when SWG is turned on.
As expected. I believe this will need to go in with the first batch of chlorine. Looks like Pool Math says I’ll need 250 ounces.


Any feedback is appreciated!
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
22,464
Laughlin, NV
Follow the non-SWCG chart until you have the SWCG running -- FC/CYA Chart

Your fill water looks like typical valley water. Do NOT add any calcium. Your CH will increase with evaporation. Do you have a water softener? You might want to see if you can plumb it so you can use softened water for make up water when necessary.

Your TA will come down as you manage your pH. During plaster start up, you will want to manage your CSI (Calcium Saturation Index (CSI) - Trouble Free Pool) so it is on the positive side of 0. Poolmath calculates your CSI.

What size Intellichlor are you getting? Best would be the IC60. Add that to your signature when you know.
 

Divin Dave

TFP Expert
LifeTime Supporter
Oct 2, 2013
5,631
Longview, Texas
Hey RS,
it looks like you''ve been doing your homework. Well done! Gotta love the test kit eh? :testkit:

Since your plaster pool is new, there is a "curing" process for new plaster as well as a "start up" process. So you will get plenty of use from that test kit. You will need to test your water daily for pH and FC. And you will need to brush it daily...maybe even twice a day. Do Not trust your PB to take of this start up process for you. No one will care as much about your pool as you do.

Do not start up your SWG or add salt for at least 30 days after the pool is filled.
Then after 30 days, add salt. Then, let the salt circulate for at least 24 hrs before firing up that beautiful SWG.

If you haven't thought about what to do with the fresh plaster, then see this link below (with more links inside it) . Lots of good info there that will be useful for you.

And if you have more questions about the start up and the care of the fresh plaster, then ask away.

 
Last edited:

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,847
Northern NJ
Keep your CSI high during your first 30 days. That means balance your pH in the range. with your high TA

The CSI is not applicable to new plaster finishes under 30 days old. It is actually necessary, to achieve a smooth and dense surface, to have about a +0.5 CSI during the first 30 days. This is because the plaster (cement paste) surface contains about 20% calcium hydroxide, which is somewhat soluble in balanced and slightly positive CSI water and can be dissolved away. The plaster surface needs to be "carbonated" before the CSI should be lowered to the acceptable and balanced range. And that generally is achieved during the first month under balanced water.


This is the PT start up guide:

 

RS220

Gold Supporter
May 24, 2019
46
Fresno, CA
Recapping various thoughts and suggestions here to make sure I have a clear understanding.

I will not add anything to increase CH, and we do not have a water softener. We’ll leave it alone and let it rise naturally, even though it is currently out of range of the recommendations.

We will keep our CSI high (targeting +0.5) for the first 30 days. It sounds like the best way to achieve this is to simply not adjust our TA or pH during this time. Since they both have high initial values it puts our CSI at +0.49, which sounds like it will be just about perfect.

We’ll try to brush twice a day, though with our schedule it will be a challenge. I’m not sure I can fit in a pre-dawn pool brushing into my morning. I leave at 6AM and am not home until 6:30 PM. Maybe it could be a soothing way to start the day, or maybe the hubby will have to be the early bird for a change.

Thank you everyone! I think we’re about two weeks out from filling. It will be interesting to see how quickly these levels change from the initial fill.
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
32,859
Sebring, Florida
Still test and manage your pH.
That is the best advice you can get. CSI is a tool to CALCULATE what you are doing but never become a slave to it and lose sight of the fact that correct pH (something in the 7's) is your first responsibility to your pool water.

You are well on top of things. Congrats to you for doing your homework and being prepared......your pool will sparkle.
 

RS220

Gold Supporter
May 24, 2019
46
Fresno, CA
Understood. It's all coming together now, and that makes perfect sense.

I'll probably try to keep pH at 7.7 to leave a little buffer room for it to climb, since it sounds like things are fairly volatile before settling down.

Will test daily for sure.

Thank you for your help, and the votes of confidence!