Pool won’t hold chlorine / traces of sand

Chlorinating, maintaining the right chlorine levels,
chlorine problems. Dichlor, trichlor, cal hypo, bleach,
granules, chlorine pucks and chlorine sticks.
jdg81
Pool Enthusiast
Pool Enthusiast
Posts: 15
Joined: Wed 13 Jul, 2022 18:33
My Pool: 18x36, 25k gallon, in ground , pentair pump / filter

Pool won’t hold chlorine / traces of sand

Postby jdg81 » Wed 13 Jul, 2022 19:04

#’s
FC 0.1
TC 0.5
TA 150
PH 7.1 (getting it up)
CYA 7
CAL 122
PHOS 1282 (working on it)



Specs
18x36
25K gallon
Pentair filter / sand pump 2019
Liner 2019

Having issue’s holding chlorine, it’s been an issue since I opened. I’ve used a lot of shock (burn out 73) almost 24 lbs, since June 6th and I’m going through about 10-14 chlorine tablets a week (chlorine feeder on 3.5). I’ve noticed trace amounts of what I believe to be sand at the bottom of the crystal clear blue pool. Adding all of the weekly maintenance chems as expected.

My neighbor said “it’s time to change your sand”. Again, the filter was new in 2019 but this is only my 2nd season with the pool. I’ve researched, pool sand is typically only good for 3-5 years depending on a few factors. How long the pump is left on (we leave it on at all times), how many seasons you’ve opened blue / green (1 blue, 1green so far). I’m not sure the last time the sand was changed. Im assuming it was in 2019.

Is it possible for old sand to trap my chlorine in the filter? See my numbers above, my pool should be holding chlorine. Aside from changing the sand I’m at a loss. Chlorine lock shouldn’t be an issue as I’m reading SOME chlorine. Any advice?


Teapot1
Pool Industry Leader
Pool Industry Leader
Posts: 1176
Joined: Thu 29 Apr, 2021 00:43
My Pool: 12000 gallons vinyl liner,

Re: Pool won’t hold chlorine / traces of sand

Postby Teapot1 » Thu 14 Jul, 2022 02:23

Your neighbour is wrong, new sand is still millions of years old. I hope one day people will stop perpetuating rubbish myths.
If you have been using as much chlorine tablets as you say your CYA figure would be much higher so something is wrong, be it your tester etc. How do you test and dip strips are near useless especially for CYA so I would get a test done by som3else to confirm then come back and we can take a look.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
rcsalway29
I'm new here
I'm new here
Posts: 2
Joined: Sat 25 Jul, 2020 17:21

Re: RE: Pool won’t hold chlorine / traces of sand

Postby rcsalway29 » Thu 14 Jul, 2022 03:39

jdg81 wrote:#’s
FC 0.1
TC 0.5
TA 150
PH 7.1 (getting it up)
CYA 7
CAL 122
PHOS 1282 (working on it)



Specs
18x36
25K gallon
Pentair filter / sand pump 2019
Liner 2019

Having issue’s holding chlorine, it’s been an issue since I opened. I’ve used a lot of shock (burn out 73) almost 24 lbs, since June 6th and I’m going through about 10-14 chlorine tablets a week (chlorine feeder on 3.5). I’ve noticed trace amounts of what I believe to be sand at the bottom of the crystal clear blue pool. Adding all of the weekly maintenance chems as expected.

My neighbor said “it’s time to change your sand”. Again, the filter was new in 2019 but this is only my 2nd season with the pool. I’ve researched, pool sand is typically only good for 3-5 years depending on a few factors. How long the pump is left on (we leave it on at all times), how many seasons you’ve opened blue / green (1 blue, 1green so far). I’m not sure the last time the sand was changed. Im assuming it was in 2019.

Is it possible for old sand to trap my chlorine in the filter? See my numbers above, my pool should be holding chlorine. Aside from changing the sand I’m at a loss. Chlorine lock shouldn’t be an issue as I’m reading SOME chlorine. Any advice?
If test #'s are accurate then you're not holding chlorine because your CYA is so low and unable to stabilize the chlorine and being consumed almost immediately from UV. What are you using for testing? It is a good idea to get a reliable test kit for yourself and not count on others. And as Teapot said strips are garbage. I have a Taylor K-2006 and I would recommend it to anyone wanting to do their own testing.

Sent from my SM-G996U using Tapatalk
jdg81
Pool Enthusiast
Pool Enthusiast
Posts: 15
Joined: Wed 13 Jul, 2022 18:33
My Pool: 18x36, 25k gallon, in ground , pentair pump / filter

Re: Pool won’t hold chlorine / traces of sand

Postby jdg81 » Thu 14 Jul, 2022 10:28

Testing numbers were provided by a pool store’s testing system. Water goes in, it’s spun around, page is printed with numbers and recommendations of what chems to use. What would good stabilizer numbers be, the report (numbers) from the pool store indicated 76 was an acceptable level to hold chlorine. Thanks for your input
Teapot1
Pool Industry Leader
Pool Industry Leader
Posts: 1176
Joined: Thu 29 Apr, 2021 00:43
My Pool: 12000 gallons vinyl liner,

Re: Pool won’t hold chlorine / traces of sand

Postby Teapot1 » Thu 14 Jul, 2022 11:05

Ok, thats LaMotte spin tester. I wonder if they have calibrated it recently?
Forgot to say dont worry too much about your pH it will get back into the normal zone with more chlorine added so dont adjust the pH for now. 76 is generally high, obviously depends on your geographic position middle of a hot climate may need a little more but 30-50ppm is normal and up to 70ppm for salt chlorination.
If you can add more chlorine tablets (dichlor) increases CYA faster than trichlor or you can buy stabiliser on its own as a granular mix.
If the CYA is that low you'll loose chlorine in around 2.5 hours so try adding your chlorine at evening time and testing before sun up in the morning.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
jdg81
Pool Enthusiast
Pool Enthusiast
Posts: 15
Joined: Wed 13 Jul, 2022 18:33
My Pool: 18x36, 25k gallon, in ground , pentair pump / filter

Re: Pool won’t hold chlorine / traces of sand

Postby jdg81 » Thu 14 Jul, 2022 12:12

Currently using trichlor, can change to di and see if it helps. Chlorine is in a chlorine feeder running all day. When I shock, I shock at night, using burnout73 super chlorinator, 2-3 bags per week. Shouldn’t my pool be reading something higher than a .1 FC morning after shock?

You also mention my CYA is “high” but based on location it could be ok. Then you say I could buy more stabilizer in granular form. Wouldn’t adding more stabilizer increase my number’s?
Teapot1
Pool Industry Leader
Pool Industry Leader
Posts: 1176
Joined: Thu 29 Apr, 2021 00:43
My Pool: 12000 gallons vinyl liner,

Re: Pool won’t hold chlorine / traces of sand

Postby Teapot1 » Thu 14 Jul, 2022 13:16

No I said the pool shops recommended of 76 is high.
Yes if you have a loss overnight then you have something to treat by shocking the pool. Shocking is a process not a product. Its about raising the free clorine to in your case about 10ppm and holding that figure until your overnight chlorine loss stops
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
jdg81
Pool Enthusiast
Pool Enthusiast
Posts: 15
Joined: Wed 13 Jul, 2022 18:33
My Pool: 18x36, 25k gallon, in ground , pentair pump / filter

Re: Pool won’t hold chlorine / traces of sand

Postby jdg81 » Thu 14 Jul, 2022 14:39

Pool man just told me everyone in the area is having a hard time keeping chlorine this year due to high heat and getting 2” of rain at a time few times a month. Recommend I shock more often twice a week, no more than 5lb a week. I’ll start there

Currently using calcium based super chlorinator but feel my calcium level is a bit high (122). If that’s considered high, and I’m shocking more frequently with double(ish) the amount of shock wouldn’t that cause my calcium level to rise beyond “normal”. Is there a type of shock you recommend (sodium?) for going through with this plan?

Side note - sand in pool I feel is from lateral’s, planning to change the plumbing and the sand, why not, at the end of the season.

Tanks a TON for all your help / time teapot
Teapot1
Pool Industry Leader
Pool Industry Leader
Posts: 1176
Joined: Thu 29 Apr, 2021 00:43
My Pool: 12000 gallons vinyl liner,

Re: Pool won’t hold chlorine / traces of sand

Postby Teapot1 » Thu 14 Jul, 2022 15:08

Calcium hypo doesnt contain CYA, the only packaged product that doesnt so it will not increase your CYA which you really need to keep hold of your chlorine a bit longer but the overnight test should still be better than it is currently. Dont mix cal hypo with sodium hypo as it can explode, it is OK in the pool as its dilute.
Keeping chlorine in the pool shouldn't be that bad even in the heat so I dont accept that but I am not where you are so I will say no more.
If you have strong sun take a look at Dr Drydens products both filter media and ACO which improves sanitation without weakening chlorine effectiveness stronger the sun the better it works. I use that with CYA and it reduces chlorine consumption.

https://www.drydenaqua.com/downloads/fi ... ms-en/file
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
jdg81
Pool Enthusiast
Pool Enthusiast
Posts: 15
Joined: Wed 13 Jul, 2022 18:33
My Pool: 18x36, 25k gallon, in ground , pentair pump / filter

Re: Pool won’t hold chlorine / traces of sand

Postby jdg81 » Fri 15 Jul, 2022 08:33

Still at a loss. Added 3lbs or cal hypo when sim was fully down, checked levels before sun was fully up (overcast) and I’m still reading .1FC , .6TC? I’m out of shock and need to buy more. Do you recommend I stick with cal hypo or use something else?

Thanks
jdg81
Pool Enthusiast
Pool Enthusiast
Posts: 15
Joined: Wed 13 Jul, 2022 18:33
My Pool: 18x36, 25k gallon, in ground , pentair pump / filter

Re: Pool won’t hold chlorine / traces of sand

Postby jdg81 » Fri 15 Jul, 2022 08:34

*when Sun was fully down
Teapot1
Pool Industry Leader
Pool Industry Leader
Posts: 1176
Joined: Thu 29 Apr, 2021 00:43
My Pool: 12000 gallons vinyl liner,

Re: Pool won’t hold chlorine / traces of sand

Postby Teapot1 » Fri 15 Jul, 2022 10:17

I would then say you have a nacent algae which may bloom Or, with the CYA so low and not climbing a bacteria that eats CYA but leaves ammonia as its waste product. That can have a very healthy appetite for chlorine because chlorine is poor at oxidising ammonia. This is quite a rare situation but I have heard of it seversl times but usually after winter when chlorine levels have been low for a while. If that was the case an ammonia test kit from an aquarium shop could check test for it.
Cal hypo does increase hardness where sodium doesnt and sodium will contain CYA which you do need. Cal hypo is stronger chlorine wise though but you could just add more sodium hypo.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
jdg81
Pool Enthusiast
Pool Enthusiast
Posts: 15
Joined: Wed 13 Jul, 2022 18:33
My Pool: 18x36, 25k gallon, in ground , pentair pump / filter

Re: Pool won’t hold chlorine / traces of sand

Postby jdg81 » Fri 15 Jul, 2022 12:25

Sorry there’s a typo in my numbers, probably changing this entire thread, sorry. My CYA is a 72 not a 7. Which would be considered high right? I’m aiming for 20-50 CYA?
Denniswiseman
Pool Industry Leader
Pool Industry Leader
Posts: 2592
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Pool won’t hold chlorine / traces of sand

Postby Denniswiseman » Fri 15 Jul, 2022 13:53

Start using Sodium Hypochlorite (plain bleach)
Excessive CYA renders your chlorine ineffective and you have to use more to get the same sanitation
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm
To reduce your CYA you have to do a partial drain and refill
Continuous use of Trichlor/Dichlor will raise your CYA which means you have to raise your chlorine level as well

You really need to Slam (Shock Level and Maintain) with relation to Chlorine / CYA Chart and Recommended Pool Levels
jdg81
Pool Enthusiast
Pool Enthusiast
Posts: 15
Joined: Wed 13 Jul, 2022 18:33
My Pool: 18x36, 25k gallon, in ground , pentair pump / filter

Re: Pool won’t hold chlorine / traces of sand

Postby jdg81 » Fri 15 Jul, 2022 15:34

For a partial drain is it safe to use the waste setting on my multi valve (pvc waste pipe runs beyond my back fence) or do I need to rent a submersible pump? I’m assuming as long as I keep the water above the skimmer everything should be ok?

Refill pool, test CYA and if it’s still high start SLAM process? Once balanced are you recommending I use bleach for shock going forward? Can I still use my trichlor tabs in my feeder for everyday use?

I cannot believe my pool store said my CYA was “good” in the 70’s? They do have a bunch of kids working there though. I’ve learned a lot from this forum in just two days. Thanks for your help

Return to “Chlorine”

Who is online at the Pool Help Forum

Users browsing this forum: No registered users and 9 guests