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Thread: Deep end TA fine but shallow end TA very high

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    Deep end TA fine but shallow end TA very high

    Hi, I'm getting TA = 148 at the deep end & TA = 90 at the shallow end. The pool is an outside, in ground, typical liner pool with inward sloping sides to a 7' 'hopper' shaped deep end L=30' W=15' (about 15,000 imp. gallons) The rest of the equipment consists of multi-port valve sand filter, gas heated to 28c in season & 3/4hp pump, a 'FROG' mineral cycler kept topped up with 2 stabilised 5 way multi-functional CL tablets. Flow rate into the pool from both inlets appears & feels strong & pretty well bounces off the far side, PSI is fine, opening/closing the skimmer & main drain valves doesn't show up any suction problems. FC = 2.7: PH = 7.6: CYA = 40 & those readings are pretty consistent over the length of the pool. The pool is 4 years old, fairly lightly used most of the time but I regularly manually vacuum & backwash & never had cloudy or green water problems. I don't use additional algaecide. It stay crystal & sparkly & so working on the principle that "if ain't broke don't fix it" apart from the start & end of the season (when I it get up to 15ppm with liquid CL)... I don't shock it. I use Fi-Clor products (dry acid, soda ash) to make any adjustments, rarely need to but I AM familiarised with the different dosage techniques. (dribble, slug still water... Iv'e tried them all!!) I keep the water level about a third of way up the skimmer but occasionally let it drop & then top up with fresh tap water to keep the CYA from the tablets under control. I normally circulate overnight (9 hours) with solar cover over but have tried 24 hours 'open' (several times!) & I dunno what else to think of! I'm stood standing scratching my head!! My tap water TA is high at 138 but I allow for that to settle & then try to treat it if I have to but despite several days of recycling even 'normal' TA readings at the ends of the pool are so dramatically different. I'd be grateful for ANY opinions, comments or suggestions of what to try next. Thanks, Don.
    8 yr old outside in ground vinyl liner rectangular 15' x 30' with 7' 'hopper shape sloping wall' deep end. (Think about 14,000 US galls but not sure!) Pentair Triton 24"sand filter (filled with recycled glass beads) Sta-Rite one-a-half HP single speed pump. Two pool returns. Gas boiler. Test kits = LaMotte DPD liquid regant ColorQ Pro7... supplemented with LaMotte FAS DPD for FC/TC when slamming. Live in southern UK

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    bobodaclown's Avatar
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    Re: Deep end TA fine but shallow end TA very high

    Hi Don,
    Welcome. TA should be the same throughout the pool unless the water isn't mixing.
    Are you rinsing the vial/test tube between test? What test are you using? How are you taking water samples? Have you tried to switch the order you take the test?
    17K Kidney Shaped Pool Concrete (Diamond Bright) Pool, 3/4 hp 2 speed 115V Sta-rite Duraglas PEA5D-180L/P2R5D-181L (Impeller C105-92PS Diffuser C1-216P), 1.5 piping, Pentair CC100 Filter , Heat Siphon 100K BTU Heat Pump Pool Heater, Flow meter Blue White Flowmeter Model No. F-30150P, Hayward Astrolight SP0581N, SWCG CalimarTitanium Edition TE45 , Dolphin Nautilus Plus with CleverClean, Lakeland Florida

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    JasonLion's Avatar
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    Re: Deep end TA fine but shallow end TA very high

    Welcome to TFP!

    It sounds like your circulation isn't so good. You should have one return pointing down towards the bottom of the deep end. Also make sure the pump is running for at least half an hour before taking water samples.
    Quote Originally Posted by don222
    I AM familiarised with the different dosage techniques. (dribble, slug still water... Iv'e tried them all!!)
    How you add acid makes no difference at all in the long run. The slug method thing is just a myth. If you want to lower TA you should read the article on lowering TA in Pool School.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Deep end TA fine but shallow end TA very high

    Hi & thank you for the comments. I never was a strong believer in the slug method but I tried in anyway just to see if it was more effective. It wasn't! Firstly my testing methods: Up until recently... which is when I noticed I had a difference in TA readings, I used a simple tablet & vial kit for once a week tests & also AquaChek 4 way test strips for quick daily dip tests. But I've always been aware that my colour comparison abilities are not good, particularly with TA & PH... so I recently changed to the AquaChek digital analyser which 'reads' their 3way 'True Test strips (TA, PH,FC) & also changed to their dedicated CYA strips so as to keep an eye on that. That is when I discovered the TA problem... its likely that its always been their... nothing else has changed. Yes... I HAVE indeed switched the order of testing the ends & I'm religious at cleaning AND drying the analyser glass between every test to avoid the potential for contamination between tests & even testing after 24 hours of 'pump run' time the TA stays very high at the shallow end & spot on at the deep end. But I absolutely agree that it sounds like a circulation problem despite all appearances to the contrary, one thing I WILL try is directing the deep end inlet towards to bottom of the pool. It could be that I'm just sort of swirling the surface. Up till now they have been level but directed (as much as adjustment will allow) towards the ends of the pool. That thought as also got me wondering (as I've got a 3/4 hp pump rather than a standard 1/2hp) if the GPM's are TOO high, (is that possible?) & redirecting both the jets downwards might help in either case. Certainly worth a try anyway, a simple thing like re-directing the jets is not something I had previously considered. Thank you... I'll let you know!
    8 yr old outside in ground vinyl liner rectangular 15' x 30' with 7' 'hopper shape sloping wall' deep end. (Think about 14,000 US galls but not sure!) Pentair Triton 24"sand filter (filled with recycled glass beads) Sta-Rite one-a-half HP single speed pump. Two pool returns. Gas boiler. Test kits = LaMotte DPD liquid regant ColorQ Pro7... supplemented with LaMotte FAS DPD for FC/TC when slamming. Live in southern UK

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    Re: Deep end TA fine but shallow end TA very high

    If you have been running the pump on a regular basis of at least a few hours a day, I believe you will find the difference is simply a testing error.

    pH and TA stay the same throughout any normal pool. What prompted you to test them in different places to begin with? Did someone tell you there would be a difference?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Mod Squad Bama Rambler's Avatar
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    Re: Deep end TA fine but shallow end TA very high

    How are you getting your water samples?
    Are they coming from different depths?
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    JasonLion's Avatar
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    Re: Deep end TA fine but shallow end TA very high

    Test strips are never all that reliable, with or without a digital reader.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Deep end TA fine but shallow end TA very high

    Yes I accept that normal dip test strips may not be totally accurate but the makers of the reader strips make very specific claims of the +/- accuracy, but even allowing for that not being legitimate the fact remains that day after day the deep end (tested first) TA reads 90 and the shallow end reads 148. Testing the shallow end first EVEN on different days doesn't make any difference, its still 148, which ever way round I do it & no matter how long the pump has been running for... the readings come out JUST the same!! My method of dipping the things in the water don't change, they go in to the length of the strip, they'r given a quick shake & placed in the reader, I do it exactly as it sez on the tin!! Also the other readings stay fine! No worries I FULLY understand that it makes no sense, It seems to go against all known logic. But yes there DOES have to be a reason... TA in a given body of water should be the same... it HAS to be!! All I can tell you is mine isn't... if it was a reasonably small difference then I COULD put it down to some sort of testing error & probably wouldn't worry about it as long as it was under 120, but a 50 point 'maintained' difference done every morning & evening & every whichway round first... over what is now 3 weeks? I dunno why I test the shallow end, just curiosity I suppose (sort of wish I hadn't tho!) But hey... Iv'e now re-directed the jets downwards & I'm going to monitor what that does for a couple of days. I just can't see how it can be anything else but a sort of 'in pool' circulation problem. If it makes no difference then I'm going to get a flow rate (GPM) meter stuck in line & see if the flow rate IS as good as I think it is. One thing I can't do is start throwing chemicals at it... not yet anyway! Thanks for your thoughts & comments though, anything else you think of by all means please let me know. Thanks, Don
    8 yr old outside in ground vinyl liner rectangular 15' x 30' with 7' 'hopper shape sloping wall' deep end. (Think about 14,000 US galls but not sure!) Pentair Triton 24"sand filter (filled with recycled glass beads) Sta-Rite one-a-half HP single speed pump. Two pool returns. Gas boiler. Test kits = LaMotte DPD liquid regant ColorQ Pro7... supplemented with LaMotte FAS DPD for FC/TC when slamming. Live in southern UK

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    Re: Deep end TA fine but shallow end TA very high

    Welcome to TFP!!

    Are you testing near the return in the deep end and not near the return in the shallow? I'm thinking the acid from the pucks may be driving down your alk reading in the deep end (please, no one remind me that it would also effect the pH :P )
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    JasonLion's Avatar
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    Re: Deep end TA fine but shallow end TA very high

    Another possibility is the lighting in the two areas, if the sun is shining on the strip reader in one place and not in the other that could make a significant difference.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Deep end TA fine but shallow end TA very high

    You guys are brilliant! I don't test near the returns & I even stay away from even being opposite the returns, I test on the far side near the corner of the deep end & near the corner of the shallow end. I also test when the pump is off & the water has calmed down & is motionless. I've tested like that just after the water has calmed down & I've tested after the pump has been off for at least a day. It IS a good thought & I hate to say it but I HAVE even thought of the effects of sunlight on the reader! Your are of course quite correct in sunlight (or any bright light) being a consideration. I only press the activation button as I dip the strip & as soon as I've pulled the strip out of the water I give it quick shake, insert it on the reader correctly so as not to smear the glass, ensure its flat on the glass & even whilst I'm doing that I'm turning with my back to the sun & hovering my hand over the reader in order to to keep it in shade whilst the reader does its thing & shines its lights & reads the the pads. Ted; what can I say... fabulous!!
    8 yr old outside in ground vinyl liner rectangular 15' x 30' with 7' 'hopper shape sloping wall' deep end. (Think about 14,000 US galls but not sure!) Pentair Triton 24"sand filter (filled with recycled glass beads) Sta-Rite one-a-half HP single speed pump. Two pool returns. Gas boiler. Test kits = LaMotte DPD liquid regant ColorQ Pro7... supplemented with LaMotte FAS DPD for FC/TC when slamming. Live in southern UK

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