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Thread: Chlorine consumption seems a little erratic! Is this normal?

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    andy2510's Avatar
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    Question Chlorine consumption seems a little erratic! Is this normal?

    Hi everyone!

    Just looking for advice. Checked the pool earlier and noticed it was beginning to slime up slightly again! This shocked me somewhat, as I added the chlorine in on Sunday (I try and aim for FC 4 in my pool - using 20g of dichlorine as worked out by Pool Math). So I tested the water and FC was 0! PH was about 6.8. (70g of laundry bleach also added to try and top that up to 7.5).

    What I'm trying to work out is why the FC level dropped so low so suddenly. In the first week since refilling the pool, FC was about 2.8 (left it alone at this point - didn't want to raise CYA unnecessarily). The second week (last Sunday) it did drop to 0 however nothing slippery on the sides.

    In the last week or so though, these things happened:

    - I realised there wasn't enough water for the filter to work efficiently! The water was freezing as pump wasn't able to send it through the solar mat effectively. I topped the water up higher.
    - That top up didn't last long though as the upper filter hose popped out overnight losing about a third of the water!!! Put it back in, moved the clamp to make a tighter connection and refilled the pool. Obviously this will dilute the chlorine further. Mind you - the filter pump has been a lot quieter since filling up further and the water has been warmer.
    - (thinking about the above - warmer water means more algae growth, which means more for chlorine to do!)
    - It is warmer here at the moment - tomorrow could actually be a pool using day!!!

    I've been testing using a cheap Bestway testing it, however a (hopefully) better Pentair kit (78DPD I think) has now arrived. I haven't read the instructions yet to work out how to run the tests.

    BTW - I bought the Pentair kit as it says it does the CYA test on the web page I bought it from, the box says it does a Total Alkalinity Test. Are these the same thing or is their a mistake on the web site?

    Any thoughts and suggestions will be gratefully received!!
    Based in the UK where our pool-usable summer is 4 days long!

    8ft wide by 2 ft deep round pool with 600g/l filter and 2x solar pods (plus electric heater - rarely used!) - nothing special in comparison with most other pools here!

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    Re: Chlorine consumption seems a little erratic! Is this normal?

    Hi there,

    Am I reading correctly that you added bleach to try and raise pH?


    15k gal IG plaster w/ water feature; 600 gal spa w/ spillway; Pentair VS+SVRS Pump; Pentair FNS Plus DE Filter; Pentair MiniMax NT Heater; Rainbow Lifegard 320 In-Line Feeder (no idea what this does or how it works); Polaris 3900 Sport Cleaner (constantly on its side); Compool Lx3800 Control System; TFT-100 test kit.

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    Re: Chlorine consumption seems a little erratic! Is this normal?

    Sorry I just realized I didn't answer your question because I got stuck at adding laundry bleach for pH.

    If you're not testing your CYA, it will be tough to know where your FC should be.

    Have you read through pool school?


    15k gal IG plaster w/ water feature; 600 gal spa w/ spillway; Pentair VS+SVRS Pump; Pentair FNS Plus DE Filter; Pentair MiniMax NT Heater; Rainbow Lifegard 320 In-Line Feeder (no idea what this does or how it works); Polaris 3900 Sport Cleaner (constantly on its side); Compool Lx3800 Control System; TFT-100 test kit.

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    andy2510's Avatar
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    Re: Chlorine consumption seems a little erratic! Is this normal?

    Hi

    I do try and go through Pool School, however things are sinking in very slowly!! I find that sometimes I learn more by asking questions in a forum like this than reading through pages of text.

    The kit with the CYA tester in only arrived yesterday, and I haven't had chance to read the instructions to find out what I have to do. What is also going to be difficult is if my CYA is too high, I cannot find 6% bleach to bring it down (I can only find <5% bleach, which makes it difficult to get an exact figure to add to the water!)
    Based in the UK where our pool-usable summer is 4 days long!

    8ft wide by 2 ft deep round pool with 600g/l filter and 2x solar pods (plus electric heater - rarely used!) - nothing special in comparison with most other pools here!

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    Re: Chlorine consumption seems a little erratic! Is this normal?

    CYA test and total alkalinity test are definitely not the same.

    Bleach, of whatever concentration, will not reduce CYA levels.

    You can change the bleach percentage number in PoolMath to correspond to the bleach strength you have available - just put your cursor in that field and change the value.

    Adding bleach is pretty much a daily activity, maybe every other day if there is hardly any sun on the pool. Adding chlorine on Sunday and finding no chlorine five days later is hardly surprising. Chlorine is a consumable and must be frequently replenished.

    Note that chlorine levels dropping to zero, plus slimy pool walls, are both bad things - the former is an invitation to algae, the latter a sign that algae has accepted the invitation.
    18' x 48" ring top pool (Summer Escapes); 5500 gallons; set up June - October, stored during winter; Intex 2500 gph pump (B size cartridge filter) Hayward 21" sand filter + 1.5 hp single speed Powerflo Matrix pump (upgrade October 2016) *** K-2006 test kit, refills from tftestkits

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    Mod Squad pooldv's Avatar
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    Re: Chlorine consumption seems a little erratic! Is this normal?

    The chlorine level needs to be set based on the CYA level and the Chlorine CYA Chart

    Feel free to ask all the questions you want. Some learn by reading, some by doing and some by asking questions. Whatever works

    Here are the basics of water chemistry,
    Pool School - ABCs of Pool Water Chemistry

    and here is a basic schedule,
    Pool School - Basic Pool Care Schedule

    With algae in the pool you will need to SLAM the pool to kill the algae, more here, Pool School - SLAM - Shock Level And Maintain
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Re: Chlorine consumption seems a little erratic! Is this normal?

    With a very small pool, it may make more sense to drain, scrub the pool interior, and then refill. Reading the links above is still a great idea, so you can get a better understanding of pool chemistry.

    You may also want to read this link
    Pool School - Guide for Seasonal/Temporary Pools
    18' x 48" ring top pool (Summer Escapes); 5500 gallons; set up June - October, stored during winter; Intex 2500 gph pump (B size cartridge filter) Hayward 21" sand filter + 1.5 hp single speed Powerflo Matrix pump (upgrade October 2016) *** K-2006 test kit, refills from tftestkits

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    andy2510's Avatar
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    Re: Chlorine consumption seems a little erratic! Is this normal?

    Thanks everyone.

    I didn't realise how quickly chlorine depletes - I was thrown by the slow decrease in the first week. As for the algae - I think I've caught it early as the sides don't seem to be that bad today (the floor is not slippery at all!). The walls were OK on Thursday night so hopefully there's nothing to fear at the moment.I'll check the CYA (if I can) and put some bleach in. I'll try working it out at Pool Math at 4% concentration and see what happens - it's labelled as <5% chlorine so it's guesswork on the actual concentration.

    I hope to keep this water going until after August - I will be putting the pool away in September before we go away so hopefully I don't need to flood the garden too often! (I planning a staged shut down process - not all of the water will be removed in one day).

    Plus... it is one of our 4 pool usable days that we have in the UK!!!
    Based in the UK where our pool-usable summer is 4 days long!

    8ft wide by 2 ft deep round pool with 600g/l filter and 2x solar pods (plus electric heater - rarely used!) - nothing special in comparison with most other pools here!

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