New Phoenix Pool with high CH levels

[sikovital]

My pool--quartz composite similar to ultrapoz-- is only 3 months old and already has CH of 750--according to the Expert the pool builder sent out. Leslie's had my last reading at 430. Because the pool is new, and the 400+ CH reading, I was already trying (acid almost every day) to keep my ph down to 7.3/7.4 (tends to drift up .1 - .2 overnight) and TA at 80-90 (cya is 80). But the Expert said the TA was too low because of the high cya, and I should keep it at 100-110. But the CYA goes up and down, depending on backwashing, what stage the tab in the floater is in. And how can a new pool have a CH of 750 already? They told me it was normal, but I was told I'd never have to drain my pool because I have a sand filter--large Pentair. Pool is about 13500, UV system, bioguard silk for back up sanitation, no salt, Barracuda G3 for cleaning. We only backwash every two weeks, and even then the pressure gauge hasn't gone up. We just do it to refresh the water in the pool. Now I've been told to drain the pool in Feb. or March because the CH can't go higher than 1000. Leslie's had my TDS at 2300 or so, with 1400 salt and CH of 430. The expert has me at 1800 TDS, salt at 1400. Do those numbers even work with a 750 CH?? (FYI: Per expert testing, Tap CH is 170; TDS 800; TA 110)

Any advice? Is this pool draining bull? The water is crystal clear, feels great, equipment function well without any build-up that I can see. There's strong flow from the returns, even on the lower speed. Since the first few weeks we had the pool filled, there has been a white calcium build-up at the water line and on the tile grout that we've had to scrub off, but we haven't even had any white line at the water line for over a month. I don't want to screw up the warranty --or my interior-- but it doesn't seem normal that I'd have to drain a brand new pool. Maybe with old pools and pools with cartridge filters, but a new pool with a sand filter. Something is just not right.

I have also had problems with testing from local pool stores. Have learned that neither Leslie's or B&L test their reagents against a standard. They don't seem to follow the kit instructions either. They do so many all day long, I think they're sloppy. So, chances are none of us is getting a good reading. They really should go to a computerized system. Calibrating the computer a few times a day would take less time than their inaccurate test kit testing. I bought a commercial kit and had it tested against standards because I was tired of dealing with the different readings from different places. How can you balance your pool if the numbers are wrong? Not even sure I trust my own testing. Does anyone know of a place in the Phoenix area you can take your pool water for a professional computer test--even if they charge for it?

Thanks for any advice you can give me. I'm at the end of my rope.

 

[257WbyMag]

You need a good test kit of your own. Please purchase a Taylor K-2006 or a TF-100 from tftestkits.net. You will not find either kit in a pool store.

There is nothing wrong with your TA. In fact, running a lower TA is one way to deal with running a pool that has high CH. The expert seems like a not-so-smart-person. Here's why...1.) TA and CYA have nothing to do with one another, 2.) Whether or not you have to change out water has nothing to do with the fact that you have a sand filter, and, 3.) CH, which is the amount of calcium metal in solution in your pool water, doesn't magically stop at 1000 ppm. It can go much higher than that and we have seen lots of people here who have had much higher levels. While we're at it, TDS is a useless value and means nothing. Only CH is helpful.

Having a high CH can and will lead to scaling on pool surfaces. It's a matter of time for you before you really start to notice them. You can keep things in check by managing your pH and your TA like a surgeon, but it takes a lot of work and that includes the most accurate drop-based testing that you can get. So, you need to get that test kit, read Pool School, and continue to post your questions here. Another thing that you can do is check around for reverse osmosis outfits in your area. RO services are beneficial in the fact that they can come to your house, filter out all of the CH in your pool water, and do so without you having to resort to draining a drop on your own.

 

[sikovital]

Thanks for the info. I did buy and tested my Taylor K2005 against standards. It's good. According to the expert, my TA had dropped to 60, but I was getting a 90 reading, so . . . And I thought CH was just calcium--at least that's what this site's definition says. The guys at Leslie's checked my pool for metals--showed 0.
What I really want to know is why this happened so fast? Is it normal for a new pool owner to have to drain after only a few months. I don't want to be watching my pool like it's in intensive care. I'm tired of checking the Darn water chemistry every day. This is not what I was told by the pool company. Once a week testing, never have to drain because i have a sand filter.

 

[chem geek]

You can see the annual pan evaporation rate map to see that in Arizona you've probably got around 100" or more annual evaporation. During the summer, it's more than the average so perhaps 1/3" to 1/2" per day (does that sound about right?). Over 3 months that would be 30" to 45" of evaporation and refill. If your pool has 4.5' (54") average pool depth, then with 170 ppm CH fill water the CH from evaporation and refill would increase CH by 94 to 142 ppm. So that doesn't explain the larger rise you saw. By the way, the Phoenix water quality report shows Total Hardness from 164-291 ppm, but Calcium Hardness (CH) will only be a part of this, though usually 2/3rds to 3/4th (the rest is magnesium) so 170 ppm is consistent with the average and 3/4th being calcium hardness.

It is possible that the CH rise came from plaster dust in the pool if they did not use a better technique such as a bicarbonate startup. The CH rise can also come from using Cal-Hypo for chlorine, but you were using tabs in a floater and silk sticks, both of which increase CYA, but not CH.

Once you get your pool in better shape, you shouldn't need to check it so frequently, but just know that if you continue to use tabs as your primary chlorine source, your CYA will build up over time and allow algae to grow faster than chlorine can kill it unless you spend more money on algaecides or phosphate removers or raise the FC target higher as the CYA rises. The alternative is to use chlorinating liquid or bleach as your primary chlorine source, but you have to add that pretty much every day. There are ways of automating this with The Liquidator or with a peristaltic pump or one can get a saltwater chlorine generator.

 

[sikovital]

Thank you Mr. Chem Geek for the info. I knew there had to be something off. Expert told me it was normal for the pool surface to be depositing so much calcium into the pool. Seems like the start-up guy used bottles of acid to drive the ph down for the first three days, and then he came back and added bags of a powdery substance (must have been baking soda, but I can't remember what he said it was) to bring the pH up. Is this what you were talking about? He also added a scale inhibitor, which I thought was also supposed to control calcium build-up. Or does that depend on which type of agent used. I think there is something intrinsic in this surface which causes it to shed all this calcium. I think once it settles down, it will be a good surface. It's beautiful.

On some days we'd lose l/4" - l/2" of water, and then at other times it seemed the water level just stayed the same. We had all that rain, and we don't splash too much, just the two of us. Our water bills didn't go up at all compared to last year when we didn't have the pool, so I don't know.

Our average depth is 4.75, 13600 gal. So, what would a normal calcium range be for a pool slightly over 3 months old?

I don't worry about the CYA build-up or algae. We lose 20-30 points of cya after a backwash, and we have a UV system running with the pump on low speed at least 7 hours during the day and 4 hours on cleaning during the night. UV kills 99.9% of everything, including algae. We only have to keep chlorine levels at .5 - 1, so I only use a tab every 2 l/2 to 3 days. Also, do occasional supplementation with liquid chlorine when I want a quick rise in the chlorine level, but I understand that contributes to TDS, which depending on who you speak to is a problem-- or isn't. This pool industry really needs one agency that dictates standards and training for a particular region, so everyone is on the same page. The pool chemistry industry is a consumer's nightmare. I've never seen anything worse, and I used to work for lawyers-- and at least lawyers have State Bars looking over their shoulders.

I have read articles from the different associations--National Spa & Pool Institute, National Plaster Association, Independent Pool & Spa Service, American National Standard, Association of Pool & Spa Professionals--and they all have slightly different numbers when calculating LSI, what % to use when figuring how much of the CYA to take out of the TA reading. That in itself seems to be a point of contention. In the book that came with Taylor's test kit, it says they recommend using a TA reading after calculating the CYA out, but that others in the pool industry disagree. It's the first I've heard of it.

My biggest problem is keeping the PH down and the TA at 100-110 (before the cya adjustment). I'm putting in 13 oz of acid every day, sometimes 17 oz. just to keep it at 7.4-75. If I put in more acid, I'm driving down the TA, and overnight the PH goes back up to 7.6. Adding baking soda to raise the TA brings the acid back up, not much though. It just seems since I've been keeping the TA higher (pursuant to expert advice) that my ph is actually less stable than when I was keeping it at 80-90. I was at the point where I was only putting in acid every other day and it was staying in the 7.4/7.5 range.

Oh, and I have phosphates--500 or so. Only treated it once-- which also lowered the CYA level--brought it down to 100, and then it was back up to 500. Seems to be staying there. Don't know what is going on there. That, apparently, is unusual for a new pool, as well.

I added Beautec Total Scale & Stain to control the calcium build-up until it's cool enough to drain.

So, bottom line. I drain l/2 to l/3 of the pool water in Jan. or February. By then the calcium shedding should stop, and I can count on a few more years before I have to deal with this nightmare again?

Thanks again for your help.

 

[dmanb2b]

Welcome to TFP. Chemgeek will certainly be able to more technically (scientifically) explain this, but if this is an outdoor pool, your UV system is not doing anything that strong AZ sunshine is not already providing for free.

If you lose 20-30 "points" of CYA per backwash, you must have high CYA, unless you define point as a percentage and you are actually draining 20-30% of your pool water. Otherwise, losing 20-30ppm of CYA in a single backwash is a lot.

Your TA is too high and as a result it is driving PH up. Typically a trichlor dosed pool does call for a bit higher TA level (Pucks are acidic), but if you insist on only maintaining 0.5-1ppm FC they are not having much effect on your PH. BTW, even with the UV system, unless you have low CYA, FC of 0.5-1 is not high enough.

Phospates are almost never an issue if you maintain an appropriate amount of FC. We have plenty of pools documenting high posphate levels do not increase FC demand. It's simply an algae nutrient and adequate FC keeps algae from growing regardless of how much nutrient there may be in the water.

Finally, the only way to reduce CH and CYA levels is partial draining or Reverse Osmosis treatment, if available.

Hope this helps some.

edit: my apologies, I missed that your CYA level is at 80ppm...a bit high, but still manageable. That said FC of 1ppm with CYA at 80ppm, is WAY TOO LOW. CYA levels directly impact the effectiveness of FC and it's ability to sanitize. I forget the exact math, but 1ppm FC with zero CYA has something like 20 time the strength of 1PPM FC and CYA of 80PPM.

 

[jblizzle]

I am just going to add (since I do not think any has yet), that the K-2005 is NOT the same as the K-2006 kit we recommend. You need to order the FAS-DPD chlorine test to add to you kit ... that is a critical test and will make your kit the equivalent to the K-2006.

You can find just that test at tftestkits.net as well.

 

[chem geek]

It's a sign of a not-so-good plaster job to have so much Calcium Hardness (CH) rising. onBalance can tell you much more about that, but it sounds like you had an "acid startup" which tends to put more calcium into the water at the expense of having a softer not-so-great pool surface. I can't tell you what's "normal", but a bicarbonate startup would have minimal rise in CH.

The UV system only kills what gets circulated through it. It does absolutely nothing for bacteria and algae on pool surfaces. Most bacteria like to attach to surfaces since that is when they grow and some algae tends to clump and stay at the bottom of the pool or on walls. Also, in the time of one turnover of, say, 4 hours, bacteria can multiply by a factor of over 65,000 though algae will only roughly double. You already get plenty of UV from sunlight and when it breaks down chlorine it produces powerful hydroxyl radicals. There is no need for UV in an outdoor residential pool.

TDS is not a problem. As for the saturation index, just use The Pool Calculator for that. The TA most definitely needs to get adjusted by the CYA for the saturation index calculation, but The Pool Calculator does that for you automatically and accounts for the pH in that adjustment as well. Stop listening to these inconsistent sources of information since most apparently are wrong.

As was noted in posts above, a lower TA will be more stable in pH because TA is a SOURCE of rising pH due to greater carbon dioxide outgassing. TA is mostly a measure of how over-carbonated the water is and over-carbonation has the pH rise unless you are using a net acidic source of chlorine. When using chlorinating liquid or bleach, you usually don't want your TA to be above 80 ppm if you want the pH to be reasonably stable.

The increase in CH should slow down by next year. At that point, your main increase in CH will be from evaporation and refill with water that has CH in it.

 

[sikovital]

So much information. What does FAS DPD test for and how will it help this situation? I've already got $85 into a test kit, so I'm not inclined to spend more unless it's going to significantly reduce the time I have to spend on this baloney.

What is "on-Balance"?

I went with a company who has an award-winning plaster guy. Didn't think the quart composites had much plaster--polymers, quartz, and who knows what else. So how did they mess this up? Bad luck. I'm cursed.

The water in my pool turns over twice in 24 hours-- once on the 4-hour cleaning system and again on the 7- 8 hours of circulating speed during the day. The water on the top doesn't stay on the top. It would eventually be pulled in and recirculated and disinfected by the UV. UV light is concentrated on the water as it flows through the UV light and kills 99.9% of everything. The water flowing back into the pool is drinking water clean. The point of having a uv system is not having to use much chlorine. Normal ranges are listed at 1-3ppm. I've kept my chlorine at .5-1.5 all summer, and the pool is sparkling clear. Expert told me .5 - 1 is good enough. Wouldn't the Barracuda suck anything off the sides and bottom, which would then get circulated through the UV? I also brush the sides and steps a couple of times per week with the water circulating so that anything on the sides will get run through the UV as well.

I have been using the pool calculator. Love it. But I still do the LSI calculation since that's what the pool builder recommends.

As far as the CYA, it was at 80. We backwashed about l/2", and it went down to 60.

I agree that the TA should be in the 80-90 range, but is that before or after subtracting out the percentage of the CYA? The builder's manual doesn't discuss it, but their expert told me to keep it at the 100-110 to compensate for the CYA. Everything I've read says that a proper level of TA helps stabilize the PH, but that at higher CH levels, one should decrease both PH and TA. Makes sense because the PH was holding much better when I kept the TA lower.

I don't think I can do this for a year--especially when I won't be swimming in it once it gets cold. No reward for the hard work. I'm driving myself nuts as it is. Ready to drain and fill with dirt.

Thanks everybody.

 

[chem geek]

If you are diligent at brushing the sides and bottom of the pool, then yes you can slough off some algae to get it circulated so that it gets killed unless it's the kind that clumps and resettles (yellow/mustard algae does that a lot, but there are some forms of green algae that do as well). Bacteria are quickly killed by even low chlorine levels, but you couldn't get away with zero levels since they reproduce too quickly (i.e. faster than it takes to get circulated to be killed). Commercial/public pools do not allow a lower chlorine level just because of a UV system since that doesn't help at all in killing bacteria quickly to prevent person-to-person transmission of disease (usually via the fecal-to-oral route), but this isn't usually much of an issue in a residential pool where you typically don't have dozens of strangers using the pool (one of whom may be sick).

UV systems have some use for indoor pools in reducing combined chlorine since there is no sunlight to help break them down. UV and ozone can also be useful in high bather-load pools such as commercial/public pools since they can help to oxidize bather waste thereby reducing chlorine demand and they can also help to kill the protozoan oocyst Cryptosporidium parvum which is very chlorine resistant (but as an oocyst, it does not reproduce in the water). However, in a residential pool the bather load is so low that you don't even notice chlorine demand from it most of the time and instead the chlorine demand comes mostly from the breakdown of chlorine from the UV in sunlight.

onBalance is the username of a person on this forum who has done experiments on plaster and written articles about it. See this thread, for example.

You should target your TA to be lower if your pH tends to rise. To compensate to keep the saturation index near zero, you can just have the Calcium Hardness (CH) and/or pH target be higher to compensate. For The Pool Calculator, you put in TA as measured. The calculator automatically adjusts the TA for the CYA that you entered as part of its internal calculations -- you don't have to do that. Anyone that understands the saturation index would know that you can compensate for one component of the index with another component -- the builder's "expert" doesn't sound like he truly understands how this works.

The FAS-DPD is a chlorine test that can measure up to 50 ppm so is not limited by the usual 5 (sometimes 10) of the DPD test kit so it's very useful if you ever need to shock the pool. It is also much more accurate when done visually since with FAS-DPD you count the drops and can have accuracy of 0.5 ppm or even 0.2 ppm depending on sample size. It distinguishes between Free Chlorine (FC) and Combined Chlorine (CC) much more readily. Click on "Pool / Spa" on the left hand side of this webpage and scroll down to "K-2006 Complete™ Kit with FAS-DPD" and then click on "To Test (Free and Combined) Chlorine using FAS-DPD" to see a demo. I don't know what kit you bought that was $85 and didn't have FAS-DPD since the Taylor K-2005 DPD kit isn't $85. At any rate, you can get just the FAS-DPD by itself such as the one from TFTestkits.net. However, this won't be faster for measuring. If you want the fastest measurement and don't care about accuracy, then test strips would do that but will often give completely bogus results depending on the test.

As for keeping the water warmer so you can swim longer (unless by cold you meant the air temperature), you can use a solar cover to keep heat in the pool and you can use a solar system to help heat it.

 

[sikovital]

The kit is a Taylor K2005 and was 83.99. Has the usual, TC, FC, pH TA plus CH & CYA. I know they're cheaper on line, but I didn't want to wait. I don't measure chlorine that high, so I don't think I need or want a more complicated chlorine test. And test strips are bogus. That's why I began using a kit. Couldn't read the strips. Half the time the colors don't match up. But the chlorine test is about the only one that the strips do seem to be in the ballpark.

Because of the UV, my free chlorine and total chlorine have always been the same so far. And again, the pool water is sparkling, brilliant, and clear. The UV gets rid of all the chloramides, so at least to date, I haven't had to shock the pool. During the hottest part of the summer, I kept the chlorine between l and l.5. I've had it at .5 during the day when the UV is running, but it usually spikes up to 1 once the sun goes down. Wouldn't it take more than a day for algae to form? Remember all of the water in my pool is running through the UV twice per 24-hour period, and as soon as that water hits the UV light, any algae is killed on contact immediately. The UV also kills chlorine-resistant bacteria. The use of UV in residential swimming pools is very recent because Trident just came out with a smaller model for residential that is economically feasible, so I don't think many people in the residential pool industry know much about it yet. People at the pool stores keep insisting that it's an ozone generator, that it's the same thing. I gave up arguing.

I thought the same thing about the CSI/LSI being in balance by compensating for higher or lower levels with another component of the index, but then I read in the APSP Service Tech Manual 2010 that "the SI is only a reliable index of water quality when the individual parameters are within their recommended ranges." The article used an example of plaster corroding with a high pH because there wasn't sufficient calcium in the water.

The "on Balance" article was disturbing. I hope my pool doesn't fall apart in 5 years. I have to stop reading this stuff. Not helping me sleep better. At this point, there's nothing I can do about it. The pool is already built.

And yes, by cold I meant air temp. Once it's in the low to mid-80's, being a desert rat, I probably won't want to get in the water, but you never know. Won't the colder water slow down the calcium build-up? Maybe I'll just get a wetsuit.

Thanks again.

 

[chem geek]

Combined Chlorine and Testing
The Combined Chlorine in my pool is almost always <= 0.2 ppm, the limit of measurement of the test using a 25 ml sample. This is true for most of the thousands of outdoor residential pools properly managed on this forum and without any UV systems (most people use a 10 ml sample so know they have <= 0.5 ppm, but if they used a 25 ml sample I bet that most are <= 0.2 ppm and some are <= 0.4 ppm). If your CC is spiking up to 1 ppm when the sun goes down (and I presume when your pump turns off), then you may be on the edge of algae growth due to your low FC level relative to your CYA level and the UV system is barely holding that back. However, with your DPD test, you really can't reliably determine the CC accurately since as a visual comparator test of intensity of pink/red, it's not very accurate.

Sparkling Clear Pools With No Regular Shocking
The pools are sparkling and clear as you can see from the ones shown on the TFP main page (mine is shown here and here). Also, no one on this forum shocks their pool on a regular basis. I have not shocked my pool at all this season. If one maintains the proper FC for their CYA level as described in the Pool School, then not only are bacteria killed very quickly, but algae is killed faster than it can grow so one does not need to shock regularly nor need any algaecides, phosphate removers, flocculants, clarifiers, enzymes, etc.

Pathogen Kill Times
See this table for chlorine kill times. Most bacteria are killed very quickly. The only ones that would not be killed faster than they reproduce in pools with an FC that is around 10% of the CYA level are the bacteria Burkholderia pseudomallei and Vibrio cholerae (rugose strain) which are both uncommon. The bacteria normally found in pools are those shed by bathers which are fecal bacteria and bacteria on the skin that are killed very quickly. Viruses are all killed fairly quickly with the slowest being Poliovirus that would take about an hour for a 4-log reduction (99.99% kill) with the FC at 10% of the CYA level. The other pathogens that aren't killed by chlorine at normal levels are the protozoan oocysts Toxoplasma gondii and Cryptosporidium parvum, but they only get introduced into a pool by someone who is sick with this parasite and has diarrhea to release it into the water (and in practice, one only sees Crypto and only in some commercial/public pools). See this link for further kill times.

Algae and Turnovers
As for algae, do the math. Even if we assume that your brushing sloughs off nearly all the algae every day, then during one turnover of the water under ideal perfect mixing conditions only 1-e^-1=63.2% of the water gets passed through the UV system. It's not 100% because some of the water that gets circulated goes through twice, a smaller amount goes through three times, etc. Two turnovers is 1-e^-2=86.5%, three turnovers is 95.0%, four turnovers is 98.2%, five turnovers is 99.3%. Algae double in population in 3-8 hours when they have plenty of algae nutrients. If we assume that 100% of the algae is killed when exposed to the UV system, the algae population is reduced by 63.2% in one turnover of the water. So to prevent the fastest algae doubling in 3 hours, the turnover rate would need to be no longer than 4.3 hours and you'd have to be running the pump continuously 24 hours. Now in practice, the algae don't grow as fast at night when there is no sunlight (they do metabolize some from energy that they've stored and eventually will be killed if there is no sunlight). Nevertheless, you can see that a pool with UV would be on-the-edge if algae were growing at near-ideal rates with plenty of algae nutrients. We've had reports of pools with UV and others with ozone that had algae, but since there are so few pools using UV or ozone it's not a good sample size and some pools were attempting to run with no chlorine at all thinking that the UV or ozone could be used instead of chlorine.

Chlorine Can Be Very Low Cost
I use only 12.5% chlorinating liquid in my pool (some others use bleach which can sometimes be less expensive or more available) and a small amount of acid. That's it. $15 per month for my 16,000 gallon pool, but I have a mostly opaque electric safety cover so my chlorine usage is low at around 1 ppm FC per day, but even for the more typical average of 2 ppm or so per day it's still cheap.

Chlorine Accomplishes Most of the Claims of UV/Ozone
I know that you are trying to justify the purchase of your UV system that your pool builder recommended, but it just doesn't do much good in an outdoor residential pool exposed to UV from sunlight. UV has been around for residential pools for some time and though it was more expensive in the past, there are pools that had them and some people on this forum have them. Since you've already got yours, I'm not saying to take it out, but rather that it just isn't doing as much good, in practical terms, as you think. It's not worthless -- just something that isn't normally needed for outdoor residential pools. If someone wants it, that's fine, but you shouldn't think that only UV solves the problems you mentioned of avoiding CC and regular shocking, having clear water, and preventing algae growth all of which are easily done with chlorine alone if the FC is at the appropriate level relative to CYA.

Saturation Index
The APSP service tech manual is wrong if they say that at a zero saturation index that plaster still dissolved when the pH was high but the CH was low. If the CH gets very low, then one can't get to a zero saturation index at reasonable pH so I'm not sure what values they were looking at in their example. onBalance has done numerous experiments regarding the saturation index and found it to be reliable, though in practice well-made plaster coupons tested in controlled water tanks are fairly tolerant to somewhat aggressive water conditions, but poorly-made plaster coupons were not. Remember that the APSP is not a completely trusted source since they do not disclose the chlorine/CYA relationship nor many of the other facts some of which I described in the Certified Pool Operator (CPO) -- What is not taught thread (CPO is done by NSPF, but APSP also has courses that have similar lack or proper or correct disclosure).

Continued Use of Trichlor Tabs/Pucks
For every 10 ppm FC added by Trichlor, it also increases CYA by 6 ppm. So even if you were using only 1 ppm FC per day (due to your low FC target), the CYA would increase by 18 ppm per month if there were no water dilution. If the CYA level rises and you don't raise your FC target proportionately, then the active chlorine (hypochorous acid) level will drop and may not be able to kill algae as quickly so you could get behind in spite of having the UV system. If this happens, you may first notice a higher than usual chlorine demand requiring you to use more tabs and turn up the feeder in order to maintain chlorine levels. Then the pool may start to turn dull and possibly cloudy, though the UV might keep things in check somewhat, but as I wrote we've seen pools with UV systems have algae when there FC was zero.

 

[sikovital]

Okay, again lots of information. But my CC is not raising after the sun goes down--it's the FC. And the TC is the same as the FC. It's based on color, so it's subjective to some point. My kit tests for DPD chlorine .5-5. I just noticed that the FC gets a little higher after the sun has been down, because the trichlor tabs in the floater aren't fighting the sun anymore. I tried using only liquid chlorine for a week during the summer, but I had to put it in every day and that's more monitoring than I wanted to do--considering I was adding acid everyday. I'll switch to the liquid chlorine after the temp drops a little. It's still pushing 100 here. The CYA goes down after we backwash. And at 50-60 ppm. the CYA doesn't seem to work very well stabilizing the chlorine. With CYA at 80 -100, I maintained a steady FC level of l to l.5 using 1 tab every 3 days in the heat of summer. I only had to supplement with liquid chlorine a couple of times when I was going to have a friend's kids in the pool.

I also noticed that the CYA went down after we used Phosfree once. I know, it's questionable whether phosphates need to be treated at levels under 1500-2500, but we were newbie newbies, and the rate spiked to 1000, so we used the phosfree. It brought the level down to 100, and then it was back up to 500, which is where it seems to stay, so I'm not going to worry about it either.

I'm going to target the FC at 1 -1.5, won't let it drop past the l/2 mark in the winter--if we have a winter. The documentation I've read about the UV shows that it kills 99.9% of everything, but you do need to keep chlorine in as backup. Before I decided to have the UV installed I read about it in several publications--besides Trident, and they all had nothing but wonderful things to say about it. I guess if we get algae, I'll know it was all baloney. But I can't worry about that right now. Until I get this ph stabilized and the plaster settled down, and the pool draining early next year, I have enough to obsess over. If I have to worry over chlorine and algae, I might as well take the UV out. The whole point of having the UV was being able to swim without getting wrinkly fingers and itchy skin. And yes, when I had the FC levels at 3+ when we first started, we got wrinkly fingers, itchy, dry skin, and my husband's eyes burned and his hair got weird--not from chloramides. There was no chlorine smell because the UV gets rid of the byproducts. I'm finding it hard to digest the concept that a direct UV light concentrated as the water flows through it is the same as the sun hitting a 14K gallon pool of water from billions of miles away. I guess we'll see whether we get algae or not. I'll let you know what happens.

And in defense of The Expert, he's been around a long time and is highly regarded in the pool world. He's also a charming person and took a lot of time to explain the pool chemistry, testing, etc. to me. I think he may have been right about moving the TA up a little higher. The Ph is more stable with the TA around 100 and the CSI numbers on the pool calculator look great. I'm good for now. Thanks for all your help.

 

[dmanb2b]

Good luck