Algae-No Chlorine Level-Help!

[debbadepp]

Hello, I am new,so sorry if my question has been 'done' before! We opened our 16x32 (Aprox 15,000 gal)inground pool couple weeks ago, Noticed some algae, but nothing unusual, water clear. Next morning pool looked like giant alka sletzer was dissolved in it--couldn't even see bottem. PH was slightly low, lowest acid level. Pool store had me raise PH, add Alk+, green algaecide, shock, backwash. Following week noticed slimy sides, still no chlorine. They had me pink algaecide treat,, shock, backwash. Still no chlorine level. They had me add 4 lbs stabilizer. Next week noticed yellow 'paint brush' like streaks all around water line and cloudy looking stuff laying in the liner seams. Called store owner, she said sounds like mustard algae and the stuff in seams is dead algae (looked like dissolving toilet paper when brushed). She had me shock 4 nights in a row, 32, oz, then 20 following nights. I got chlorine reading the first day, and then nothing since. Yesterday, I noticed some yellow algae AGAIN. I cleaned and shocked last night. Still no chlorine reading. My ph is 7.2, acid level is lowest color on strip. The pool water is always clear. I use granulated chlorine (Zappit 73) Sorry to be so chatty, but I wanted you to know how much I've done. PLEASE HELP! Thanks, Debbie

[PaulR]

There are two things that consume chlorine: sunlight, and contaminants in the water (algae, ammonia, bacteria etc). The store had you add 4lb stabilizer which would raise your CYA by about 30ppm, according to the Pool Calculator, and that was around two weeks ago so it should all be dissolved by now. Therefore, we can figure sunlight is costing you something normal, like 1-2ppm FC per day. So, most of what your chlorine is eating would be contaminants.

Zappit 73 is 73% cal-hypo, each pound is worth about 6ppm FC in 15k gallons so 2lb would be about 12ppm. That's a reasonable shock level for 30ppm CYA. The first thing is, you can't just dump chlorine in once and be done with it; "shock" is a process, not a one-time event or a product. You need to use enough chlorine to bring up your chlorine and keep it there until the chlorine level holds overnight.

The best way to manage this is to have your own test kit, such as the Taylor K-2006, which is capable of measuring the high FC levels necessary for a shock treatment.

The second thing is, cal-hypo is okay for short-term use but it adds 7ppm calcium for each 10ppm chlorine, and eventually your calcium hardness will get too high (because the calcium doesn't go away unless you remove and replace water). So for the long term, I prefer "liquid chlorine" or its grocery-store equivalent, plain unscented bleach, as a chlorine source.

--paulr

[debbadepp]

Thank you so much. So, do you recommend I use 2 lbs every night until I am able to get a chlorine reading in the morning? How much do you recommend after that daily to maintain and how much bleach would I use daily and to shock if I decided to go that route. I appreciate your help.

Debbie

[PaulR]

I recommend you get your own high-end test kit and add as much chlorine as necessary, as often as necessary--probably multiple times per day at first--to maintain a high shock level until the problem clears up. After that, you change your chlorine target level to a normal level, and add as much chlorine as necessary, as often as necessary--could be every day or two or three--to maintain the normal level at all times.

It is not possible for me to tell you how much you will need, because that depends on precisely what's happening with your pool on any given day. It's like asking me how much gas you'll need to operate your car; that depends on how you drive, how much you drive, and what kind of mileage you get. You have to monitor it yourself, and do what's necessary so you don't run out.

--paulr