Why I support TFP

[kkendall]

As my pool was going in, the thought of maintaining the pool caused me great distress. I was so worried that I was going to have a mosquito farm because I knew NOTHING about pools and what it took to keep them clear and pristine.

I have since learned that there are:
* people that know their stuff (as we see here on this site!)
* people that know nothing at all (that was me)
* people that know less than nothing (those are people that think they know, but in reality don't)

I noticed over the course of the last month and a half, I have had to add muriatic acid every few days to keep pH below 7.8 (it kept kreeping up).

I also observed that the TA went from 110 when we started up (beginning of Sept), to 90, to 80 ... to last weekend being 60. I have concluded that having to keep pushing pH down every few days also causes TA to slowly drop over time. Reading about is is one thing, seeing it in my test every week really drove it home!

Fix - added a couple pounds of baking soda yesterday - TA @ 90 today
(also had to add some muriatic acid today to push pH back to 7.5 ... will continue to test over the next couple days and add more baking soda when/if needed to bump it back up to 90)

The CH started out at 150. (shocking considering that everyone told me it wasn't possible with AZ water).

The test results kept coming back the same over a few weeks which made me question my own testing procedure ... (after testing the tap water, it confirmed my test of 150 was right - pool store test of 250 was bogus!). So I went with my test results and added some Hardness Plus (Leslies) over a few weeks... CH @ 240 today.

Today's test:
FC 3
CC 0
pH 7.5
TA 90
CH 240
CYA 35
CSI -0.08

I can't be happier with how easy it has been (thanks to THIS SITE) to wrap my head around the pool chemistry. The TF-100 was probably the best tool I could have gotten to manage the pool. I'm also quite thankful that I'm not a pool store victim and that I found this site first.

Because of that, I don't put any mystery compounds in my pool. The pool builder put some tri-chlor tabs in a floater when they started it up. This was fine for the first 2 weeks until I saw my CYA approach 40. Then they came out and I haven't used them since.

Now, the only thing that has gone into the pool is 10% chlorine, 20 deg baume muriatic acid, calcium, and now baking soda. Gotta love it!!!

 

[chem geek]

I also observed that the TA went from 110 when we started up (beginning of Sept), to 90, to 80 ... to last weekend being 60. I have concluded that having to keep pushing pH down every few days also causes TA to slowly drop over time. Reading about is is one thing, seeing it in my test every week really drove it home!

Have you found that the amount of acid you are adding is lower when the TA got lower? If so, then having a lower TA would be more stable and you can compensate with a higher pH target and CH level for the CSI. If this is not the case, then perhaps you've still got some pH rise from the new pool surface in which case keeping the TA up at 80 ppm or so is reasonable and the addition of acid is just a requirement until the pool surface stabilizes. You should see the amount of required acid drop over time if this is the case.

 

[chem geek]

For some reason I was unable to edit my post above. I wanted to add that if the pH rise was from calcium hydroxide from curing plaster, that adding acid to maintain pH would not result in the TA lowering. When the TA gets lower from adding acid, that implies carbon dioxide outgassing. So in theory at the lower TA level you should have been using less acid over time and possibly having the pH rise more slowly as well. Do you have aeration features in the pool such as waterfalls, spillovers, fountains, etc.?

 

[kkendall]

I do have water features, but have only had them run twice (to create a nice atmosphere for an hour or so while sitting outside)... but really haven't used them much.

The amount (and frequency) of adding acid has pretty much been consistent - about 16 oz every 4 days. Almost like clockwork - add chlorine every 2 days, muriatic acid half as often. I wait to see 7.8, then add enough to drop it to 7.4 - 7.5

 

[y_not]

Chem Geek,

Could his/her ozone generator be causing this? Does it aerate like an SWG does?

OP, are you using your ozone unit?

 

[chem geek]

Ah, good catch, since an ozone unit is listed in his signature. Yes, an ozonator most definitely injects mostly air into the water so aerates it. It's also not of very much use and if anything would result in higher chlorine usage since ozone destroys chlorine (creating chloride and chlorate).

I am surprised that the amount of acid needed at the TA of 60 ppm is the same as that at 90 ppm. If the amount of acid were less, but the pH rise were still an issue, then 50 ppm Borates could help the latter allowing you to add acid less frequently.

 

[kkendall]

It's also not of very much use and if anything would result in higher chlorine usage since ozone destroys chlorine (creating chloride and chlorate)..

It never dawned on me that the ozonator would raise pH - but yeah, makes sense! duh!

I'll do an overnight chlorine drop test. The unit runs on high for 4 hours every night (and low speed in the morning till noon). I'll grab a sample after the sun goes down and test - and then another sample in the morning at about sunrise. That should give me some indication of just how much chlorine it kills (I suspect very VERY little).

 

[chem geek]

That should give me some indication of just how much chlorine it kills (I suspect very VERY little).

Well, if it lowers chlorine very, very little than that means there is very, very little ozone being generated so it would be pretty useless from that perspective as well. In general, most residential pool ozonators are woefully undersized or poorly designed. Proper ozonators for large volumes as with pools should be using corona discharge (CD), not UV, for generation of the ozone and should have air driers for the air intake unless the air is very dry (not at all humid; i.e. desert).

In residential spas, we know when an ozonator is working because the chlorine loss rate with no bather load doubles. When there is frequent bather load, the chlorine usage rate is cut in half.

 

[kkendall]

There was no measurable chlorine loss overnight.

 

[chem geek]

OK then (assuming the pump and ozonator were running overnight). So you need to ask yourself if it's putting out so little ozone and since chlorine is able to oxidize bather waste on its own then why bother having an ozonator for an outdoor low bather-load residential pool?