Pool Chemical test, the pool guy, and pool store

[EDAM72]

First, thanks for a great site with so much info, I will be becoming a supporter.

Had pool for almost a year, just had everything redone (in sig below). I am a pretty technical guy and like everything to be in spec. I started notcing discrepencies between the pool guy and pool store and conflicting information given. Decided to get my own kit and start doing everything myself (will be letting pool guy go soon).

What finally prompted this was my pool guy didn't clean/monitor the pool for 1-2 weeks, allowed FC to drop to 0. Started noticing algae on sides and in spa. Did some research, everything pointed to needing a SLAM at this point. Told pool guy, he stated to remove phosphates and then clean filter. He put in high chlorine and phos free (even thouh it says to have sanitizer below 5ppm before using). Got rid of algae and pohphates and cleaned filter out. I was annoyed it reached this point and then didn't follow recommended procedure, so started my self. Then, after , he decided to go from 1-2 pucks to 6 pucks in floating chlorinator. Then I read pucks are bad, raise cya, drop TA, and don't keep water that clear...sigh.
Also, I think they gave me way to much pump for pool, did not calculate head, water volume etc.....

So, first test (i compared my results to pool store)
FC 3.4
CC 0
CH 190
CYA 50-60
TA 70
pH between 7.4-7.6
TDS 725
Phos 0
Current water temp- 90 F

Pool store drills that FC ideal is 1-4 ppm. According to your CYA-FC chart, I need a minimum 4-5ppm and shoot for 6-9???
I am guessing the pucks were raising my CYA and lowering the TA. I pulled them out of the water.
Did an OCLT and went from 3.4 to 3, which I understand isnt too bad.
I will be buying liquid chorine now and adjusting my self, raising TA (with baking soda) at least to 80, and CH to 200.
Does this all seem correct?

Wanted to add-trying to correctly find Head, Volume of pool. Much is under concrete so I assume I estimate the pipping. Pool is oval with straight not curved sides. 31ft by 14.2 Side depths are approx: 3.9ft and 3.6 ft, middle depth 4.5ft. Spa is 6.10 feet in dia. and 3.4ft deep. Seat depth is 1.8 ft ifit matters in calc. When I filled pool it read about 11k on meter, adding 500 gallons to be safe in fluctuations nd according to measurements.

Thanks again, and look forward to being a part of the forum for my own information and to help others as I learn.
Thank you.

 

[Demegrad9]

Sounds like you pretty much have a nice path forward!

Some thoughts from me, for what that's worth. 1) You're FC of 3.4ppm suggests you're using the 25mL sample with the K-2006. Go ahead an shift down to the 10mL sample and save reagents, the accuracy is still plenty good to follow the TFPC method. 2) Sounds like you have a plaster pool, if so check the recommended levels for plaster for all your ranges, mainly you want to bump up calcium hardness up to 250ppm-350ppm. 3) Nobody cares about phosphates and TDS. And lastly 4) Don't worry too much about TA, the right TA is where pH is relatively stable, do a search to clarify this point but the general idea is that if pH keeps drifting down you use Borax or Soda Ash to pull it up both of which raise TA a little, after a while pH stops drifting down. Vise versa for pH drifting up, if so use muriatic acid to lower it which also lowers TA a little, after a while pH stops drifting upwards. Whatever TA that occurs at is the right TA.

Pool School -> Table of Contents -> Chemistry-Recommended Levels by Surface Type

 

[EDAM72]

Thanks! My pool is pebble, do I follow same recommendations for plaster (they do not list pebble)?
If so, I will look at raising FC and CH for now.

 

[triptyx]

Yes, a pebble-based pool is still plaster, just with aggregate in it. Follow the plaster based pool recommendations.

Demegrad is spot on about TA. The two main concerns with TA are how fast your pH rises (higher TA = faster pH rise), and its effect on CSI - your water's tendency to either scale, or eat away that plaster. 70 is a pretty good number. Mind your pool in the winter, as temperature drops, the CSI will also go down.

How hard is your fill water? The water in your pool will evaporate over time, raising that CH number. At 190 it's not too far below "ok", and as long as you're watching your CSI to make sure it doesn't get too close to (or below) -.6, you should be fine leaving it there.

 

[EDAM72]

Thank you, doing a CH test on fill water gives me a Ch of 90. And yes in summer without cover, I add 100 - 150 gallons every one to two days.
So, at this point I should only be increasing FC to around 5-6 ppm?
Thank you

 

[Demegrad9]

Since you said your CYA measurement was 50-60ppm, you should assume 60ppm and then your FC range is 7-9ppm.

Wow, you have a lot of evaporation. Some math in excel will tell you how CH will change. And since you have cartridge filters, no backwashing... I would have to do the math before making a recommendation. At least you can keep CH down by dumping water when you get to the point where it's too high, filling with your have 90ppmCH water will bring it down nicely.

 

[Demegrad9]

Alright, I did some math. Maybe someone can confirm this but it looks like if every week you evaporate ~150 gallons out of our 11,500 gallon pool that will increase your CH ~3ppm each week, then refilling with 90ppmCH water will bring it back down ~2ppmCH each week. So in total you should see a 1-2ppm increase in CH per week in general. This assumes you're not ever dumping water, which appears from my excel sheet here to be an excellent way for you to control CH level when you get closer to 350-400ppm

At that pace you'll be waiting 94 weeks before you get up to the mid-range 300ppm for CH. That 94 weeks is actually much longer because there's no way you'll see that same 150 gallons per week evaporation all throughout the year.

So if you've got 90ppmCH fill water, I'd say go ahead and bump up CH to the recommended range. Probably not the top of the range since you should see CH increase gradually. Also figure our your CSI and try to keep that between -0.6 and 0.6

 

[Demegrad9]

Alright, I made a big mistake. You said you have 100-150gallons of evaporate per 1-2 DAYS, not a week. With a solar cover in the northeast this summer I get more rain than evaporation so I guess it was hard to imagine the scale of evaporation here.

Okay, so we're talking more like 600 gallons of evaporation per week... So in that case you'll see 4-5ppm increase in CH per week over the summer. Quite a bit more than I earlier said, but still will take a while to get up to the recommended range. I would say add enough Calcium to get to the bottom of the range and see where your CSI is.

 

[triptyx]

Hi CSI with the measurements above is -.29, which is fine. If he maintains pH at 7.8, it's 0.

With the evaporation, there's zero reason to pay money to add calcium - his water and evaporation will do that for him just fine in short order.

 

[EDAM72]

Thanks all. Yes, I am using the Taylor Watergram wheel to figure SI (is there a better way?). With CH of 190, TA 70, and PH of 7.5 It is right around -.2. If I bump up either CH or TA it brings SI closer to 0. I am learning quite a bit quikly on the forum here, and appreciate everyone who takes time to reply. On computer and network threads I am usually helping and answering questions, roles are reveresed here!

Yes, evap here on a hot day (85-95) and keeping water at around 90 overnight has much evap. Sometimes I put cover on to keep temps up in pool if it is going to drop low over night, or I know people will be swimming early next day. I see hardly a noticble loss of water with covers on. I also use less chems over the week if I keep cover on, but I am told it invites algae as I am getting no sun (pool store says to use Fresh n clear-the non chlorine shock when i use cover-but that skews CC test with out agent that nullifes it). It is a blue cover, would clear cover fix that?

And last, this is probably a silly question that may be answered elsewhere on forum, but according to CYA chart I should be keeping an FC of 7-9. Is that high a level an irritant to swimmers, or not a factor as CYA is holding some in reserve and swimmers are not getting the full force? Same for equipment and solar cover, safe?
Thanks

 

[mknauss]

CSI (Calcium Saturation Index) is what the forum recommends over the SI. PoolMath calculates it when you enter your current test results.

A cover is a great way to reduce evaporation and lower chem needs. You should remove it every few days during sunlight to burn off your CC's. Do not use MPS(non chlorine shock). If you maintain the proper [FC/CYA]FC/CYA[/FC/CYA] relationship and brush weekly you should not have algae issues.

The target all the way up to shock level FC related to the CYA level is not harsh or damaging. In fact, the available chlorine at the FC range you show above with the appropriate CYA is far less harsh than a public pool with 1-3 ppm FC and no CYA.

For some in depth reading on pool chemistry -- Pool Water Chemistry

Take care.

 

[Demegrad9]

I'm not sure but the Taylor Watergram Wheel thing is measuring LSI which is slightly different than CSI, there's some very good thread on here explaining the history of these saturation indices. Use Pool Math link on top of this webpage. Enter your current numbers and the CSI is calculated towards the bottom.

And for you last question, not a silly question. Yes, nothing is getting full force as you say. Earlier this season I had ~120ppm of CYA so I maintained FC around 15ppm for a while. Water still feels great and you won't have any eye or skin issues as long as you don't have CC's. I've heard of other people here maintained FC's of 20+ while they tried to drop CYA. Even now I have 60ppm of CYA and try to maintain 7-9ppmFC. My last measurement was 10.5ppmFC because I didn't check for a few days and I have a automatic dispenser, but it's the water is still great. High FC really doesn't cause those issues, the 'chlorine' smell and eye irritation is usually high combined chlorine.

 

[EDAM72]

Thanks, I have ben using the pool math, and also reading all articles in Pool School.
Today's test:
FC 4.5
CC .5
pH 7.6
TA 80
CH 180
CYA 50

I will add more Chlorine today to get to desired range.
I am guessing the CC is from having landscaping done in the back. Pool cover is on, but some dirt still gets in. Once I can pull the cover I expect it will go away.

For pH, I see the guy holding it in video (manufacture website) against sky in daytime. This slighty affects way color looks as opposed to holding against a white background. What do most prefer? One way looks 7.6 other is closer to 7.8.

I think I will also research on here the auto chlorinator that works with my Pentair system.
Thanks everyone.

 

[mknauss]

Hold the pH test against a white background (paper, cheap paper plate, etc)

Do it the same every time for consistency.

- - - Updated - - -

I think I will also research on here the auto chlorinator that works with my Pentair system.

I assume that is Saltwater Chlorine Generator. Good decision. Be sure to size for at least 2X your pool volume.

 

[EDAM72]

Ok Todays result-
FC 4.5
CC .5
pH 7.6
TA 80
CH 200
CYA 50
CSI -.06
Yesterday afternoon i had FC up to 7.5 around 3pm, pulled off cover and has swimmers in pool and spa going, today at 1pm its at 4.5, so 3ppm loss. I am guessing once backyard work is done, i can start to correctly gauge normal FC loss daily for me. I'll make sure I get FC correct in evening and do over night test once work is done. Then take measurements daily in late aternoon and adjust. But for now it looks to be ok. Once garden work is done should be minimal changes.

Pool store has 12% chlorine that comes in reusable containers. Around 18 for 4 gallons, then when empty you take back and swap for full ones. I will have to see if that works bette than buying the 6% from stores or the 10% from places like home depot or lowes.

Thanks again for everyones reply. I will take the equipment questions and such to the appropriate forums.

 

[EDAM72]

Ok, its official, not wasting anymore time checking my results with pool store. Their results vary greatly sometimes from one weeek to next. Main reason I was going was to have a print out to satisfy requirements for Pebble Warranty.
And their results are often way off from mine. Possibly because the guy's eyesight isn't that great, and/or not cleaning the test items enough.
My own FC test can differ 1 ppm even if I test 3-4 times in a row. First one is usually higher. I read results can change in as little one minute once sample is pulled from pool. I'll have to experiment.

Last pool store check:
FC- 15-20 Wow -he said 20 first time-said was to high-had to dilute and got 15
TC 15-20
CH 190
CYA 100
TA 50
pH 7.8
phos 400

He said FC was way to high, needs to be 3-4 ppm. When I asked shouldn't it be based on CYA levels, he said keep at around 4 you will be good. Then proceeded to tell me to drain pool to lower CYA. I asked how CYA got so high from a few days ago when he tested when all I add is bleach I bought from him......Don't know.
He said going liquid bleach only was a trade off, as it adds more TDS, tabs add CYA.
He said he uses DPD testing for FC
So, I am done with that.

My own tests (done 2 times in a row to check myself) right after I got home from store:
FC 8.5
CC 0
CH 220
CYA 60
TA 80
pH 7.8
and just for kicks tested phos = 100 if that

Topped off pool last night-test today is:
FC 6
CC 0
CH 210
TA 90
CYA 50
pH 7.8

So, I think I am on right track. Water looks and feels great. And doing this myself is actually a little therapeutic.
So thanks all who took the time and interest in my ramblings.

 

[Demegrad9]

It helps a lot to give up on the pool store testing, the extreme variability of the results just bring confusion to the situation.

The history of TDS as I've read here is that early on TDS was being blamed for the so called 'Chlorine-lock' before the effect of CYA was well understood. TDS is of course all total dissolved solids, so salt, CYA, metals, and some other stuff I can't remember off the top of my head. Using bleach as compared to Trichlor does raise TDS slightly more than Trichlor but when you use bleach it's all salt vs when you use Trichlor it's roughly 60% salt / 40% CYA. So all in all, high TDS doesn't matter, what really matters is what makes up that TDS, if it's just salt it's fine, if it's way too much CYA than you probably have an issue...

If you confident in your CYA number of 50ppm, then just keep it in that target from of 6-8ppm FC.

Just curious have you done an overnight chlorine loss test recently?

 

[EDAM72]

Thanks, I actually just did one.
Last night was an FC of 5ppm
This mornings readings:
FC 4.5
pH 7.8
TA 80
Ch 210
CYA 50

I did the FC test 3 times in a row (like I said sometimes I get different results) and received 4.5, 4, 4.5. So I will research some items that could give me varying results. Even so it would be a max of 1ppm loss which I am reading is the minimum to be ok, with 0-.5 being ideal.

Thank for the info. If your CYA ever starts to get low, would you be ok using pucks for a time to give both chlorine and get CYA back up, or better to add just straight conditioner?

 

[peirek]

CYA will only go down if you have a replacement water event such as large rain. Evaporation will not impact CYA as it doesn't leave with the water. Pucks are fine as long as you understand how much CYA each tab is providing to your pool. PoolMath says a 8oz tri-chlor puck will add 2.9ppm of CYA to an 11,500 gallon pool.

 

[Demegrad9]

A lot of people just let CYA drift down through the season until they take a week or two vacation. You'll hear it called "Saving their CYA". The idea is to start the season with 50ppmCYA then let it drift down to 40ish or whatever. Then just use PoolMath to figure out how many pucks it'll take bring your pool back up to 50ppmCYA. Load them up in a floater, toss it in, and go on vacation. Then no need to worry about FC dropping as the tablets dissolve so slowly and the whole time you're just bringing up CYA to the desired level.