Chlorine drop

[Pgkinno]

Ok - I am a novice and any "duh" comments my way are ok - just need some un-baised help here please - ( and thank you for any response!)

Why would a perfectly clear - newly established pool - go from a desired stick reading of 3-4 to "0" 6 hours later ? pump running - pool 42" deep or less - in full sun - was shocked with a hth product (envelope) and has a 3" tab filter with the max exposure... all other readings normal - in the desired range????

AND - how dangerous is it to swim in the meantime?

Thank you for any help here!

[Backglass]

Hi,

I'm not sure what a "stick reading" is, but if you are talking chlorine levels it sounds like you don't have enough, or any CYA (aka stabilizer). Without any CYA, direct sun can remove all your chlorine in a few hours.

[pgkinno]

I turned on the filter Friday night and have basically let it run since. This morning I placed a 3" tablet of chlorine in a floater AND shocked the pool with one of those "shock" packets you can buy at WalMart - (filter running - water clear (always was) skimmer thing working fine...) I tested water pre and post - all stayed the same except the CL levels. After I put in the 3" tablet/floater - i didn't see any difference in the CL levels - I then added the shock packet (which I diluted in a bucket before adding) - CL levels went up to what looks like normal levels - 3-4 ... Six hours later I tested the water again - Hardness, pH, Alkalinity, Cynuric acid all the same - EXCEPT - NO chlorine???? What happened and what do I need to do -

Current levels before and after shocking and a 3" chlorine floater are"
hardness (200) ; Chlorine 0; pH 7.3 - 7.5 (somewhere in between the two on the dip stick)
Alkalinity 120; Cyanuric 30-50 (could be lower)

Does this help - They were all hth products?

[Buggsw]

Sounds to me like algae/bacteria in the water. If your CYA is correct it should be fine. You may need to shock and keep it at shock level for a few days until the chlorine holds overnight. Run your pump 7/24 until then.

I really wouldn't use any more tabs or pool shock if your CYA is at 50. Use regular strength Chlorox or pool store chlorine to chlorinate and to shock your pool. If I knew the volume of your pool I could tell you how much to use.

Get a real test kit or have your water tested at a pool store. Sticks are a big pain in the neck because of unreliability.

[pgkinno]

Thanks for the help - sorry i couldn't get back sooner but I wanted to wait until I had more news...
You know - I really think it is a low CYN problem -
I purchased another test kit today and there is little to no CYN - it didn't register - (not a stick kind - one with test tubes...) Pool is supposed to hold about 5000 gals - but it is less than that because it isn't complete full intentionally as we live where it can rain 3" easily in a day - It's in full sun!

I did add a generous half gallon of unscented bleach a couple nights ago - and the same thing happened - this time 'fine' overnight and in the morning - then zip (0) the next day after work - (Still might do that tonight because I don't want to go too long without a shock) Water looks fine - still clear - why I don't know - ...

So today I added about a pound of CYN and will retest tomorrow - the 3" floater is dissolving - at least half gone - so there is some chlorine going into the pool - but clearly not measureable on either testing process - stick or test tube... I've left the filter running - hoping that will help keep the water clear while I figure this out... If I am going about this all wrong - let me know - otherwise I will keep plugging away in this direction -

Thanks for all the help/comments...

[Buggsw]

Sounds like you are doing fine. Get that CYA up to 30 - 50 ppm and keep adding chlorine day and night until it get's to 30 to keep your levels up.

You can always add CYA, but you cannot easily get it out without dumping a lot of water so don't get carried away.

[pgkinno]

SUCCESS! Thanks for all your help! CYN addition worked - chlorine has held (3 ppm) through two very warm and sunny days! Will get the hang of this yet - but - You all really helped me through the learning curve... THANKS!!!!

[Buggsw]

Ahhh, good!

Now, watch it so that your CYA doesn't get too high, because you can have the same issues if it get's too high. It reaches a point that Chlorine loses it's effectiveness.

[pgkinno]

thanks Buggsw!

I'm wondering if I should just bag the tablets and keep up with the Chlorox? It's not much different in cost - but NO CYN ... I also have another question - I always assumed that when you "shock" a pool - you just added more chlorine - but my new understanding is that shocking rids the pool of "used-up" chlorine and sorta brings the water back to where it should be... Any advice?

[Buggsw]

I think switching to liquid chlorine is a good idea.

Shock is a verb, not a noun. In other words you shock your pool with high levels of chlorine to kill algae and rid combined chlorine/chloramines (that is the "used up chlorine").

You only need to shock your pool if there are combined chlorine/chloramines if you have maintained your chlorine at the proper levels. If you haven't, and algae appears, you also need to shock.

Actually, using chlorine rather than tabs or pool store shock products should be a little cheaper. Depends on the area, I guess.

I find it's cheaper to purchase freshly made 12.5% liquid chlorine at my local pool store than to have to purchase twice as much chlorox at the grocery. Tablets and pool store shock products are always expensive here. Other areas, it may be different. So keep an eye out on the prices and do the math with the chlorine.

I do use tablets when I am on vacation.