50,000 Gallon Monkey On My Back

I have a 50,000 gallon IG Vinyl pool that came with the house. I maintained it last year using the local pool shop and then found this forum. I opened it yesterday and was surprised that the algae hadn't gone crazy yet. The temperature in OK is already in the 90's. The water was dirty but not really bad. I shocked the pool and ran the pump through the night and these are my numbers from Ben's Testkit this morning:

FC - 3
CC - 0
TC - 5
pH - 6.8
Alk - 40
Cal - 300
Cya - 100

I'm currently using dy-chlor II with 3' tabs. Last year I used borax and baking soda to adjust the pool but haven't taken the leap to go to bleach. It seems staggering the number of bottles of bleach I'd have to consume to maintain the proper chlorine levels in this pool.

I'm fairly new to pool chemistry and usually mistakes with this size pool seem to cost me $$$. Before I do anything else I thought I'd get some advice on what to do next. Thanks for the forum and your help!

- Korinian

Hi, Korinian,

I'll bet we can help you get 'ole J. Fred Muggs (If you know who that is, you're showing your age) off your back, outta' the pool, and back to the zoo where he belongs!!:) :)

Man, that's a big pool!!

1. Get your pH back to at least 7.0....7.2-7.6 is better. You could be lower than 6.8 and not know it with Ben's kit.

2. Clorox is gonna' need to be your Cl vehicle, I'm afraid. (think of all the plastic jugs you'll have for cat-fishing!!)

Your CYA is too high to use any more pucks...they'll just make it worse. You'll probably have to fight pH again, too.

Calcium Hypochlorite adds calcium to your water and you've already got more than most folks....don't need it anyway.

So you end up with Clorox. One of their giant jugs (1.42 gal, I think) should move your Cl almost 2ppm.

So, what to do next? Switch to bleach. If your water tests for no CC again, download mwsmith's calculator and bring your FC up to around 10ppm.

Depending on a variety of circumstances, you'll probably need about 1 big jug per day to keep it there. If you choose to continue pucks or Cal Hypo, your water will continue to get more and more troublesome.

Dave S.

Well, I took your advice and bought some bleach. The local Walmart only had the 1 gallon size. Yesterday I put 4 gallons of bleach in and a box of borax. These are the numbers from today:

FC - 13
CC - 0
TC - 5
pH - 6.8
Alk - 50

I've added another box of borax this morning. Yesterday I ran out of the stuff for any further Cya tests. Like everyone else, I'm patiently waiting on Ben's new kits to ship. What little algae I had is dying and collecting on the pool bottom. I'm scrubbing the walls and floor of the pool twice a day. And running the pump 24hrs/day. How high do I need to keep the FC numbers and for how long? And now that I'm a bleach convert... for a pool my size... how much would you add to it daily/weekly/ and for shocking??? Thanks for all of your help.

You need more borax! Quick! Keep slapping in a box at a time until you see the pH move. Give about 4 hours of circulation time to get it evenly distributed.

Also, your math does not make sense. FC + CC = TC. You simply can not have FC = 13 and TC = 5. I think what is happening here is that you are getting the FC & CC from the DPD-FAS test, and then you are testing for TC again with the OTO test, which is topped out by your high FC level. If you use the DPD-FAS, you don't need to use the OTO test.

Since you are showing CC of 0, there's no need to keep the shock up for that purpose. When the algae goes from green to brown/gone you can let up on the bleach.

As for how much bleach to use, well, you use enough to keep your pool algae-free. Take a look here: http://www.poolforum.com/pf2/showthread.php?t=365 for the table to help you with this. For your CYA levels, it looks to be about 8 PPM.

There are 2 primary reasons to shock:

1. Algae
2. CC of 1+

Of course there are other reasons, (dead critters in the pool, fecal matter, etc) but those are the main ones. If you don't have a problem with the above, save your money and don't shock. I haven't shocked in close to a year now.

Michael

Hi, Korinian,

Quote:

---

So, what to do next? Switch to bleach. If your water tests for no CC again, download mwsmith's calculator and bring your FC up to around 10ppm.

---

Have you loaded Michaels calculator yet? It's right above this post and will answer the majority of your questions about quantities. I'll bet your pH was W-A-A-A-Y low!! :)

Dave S.

Everything seems to be working. The dead algae is collecting on the bottom of the pool and I'll vacuum to waste. I was getting the TC number from the DPD-FAS test. I didn't realize it was redundant if you combined the FC + CC. Sorry about the confusion. I've downloaded and installed the beachcalc program.

I've dumped 3 more boxes of borax in the pool and the pH hasn't even twitched. Apparently, my pH was ridiculously low. I'll continue to pour borax in and keep the chlorine up. Thanks for all the help.

Yeah, keep up with slugging the borax in there. Your pH got shoved way low by using those tablets. 50K/gal is a lot of water to get to move the pH. It will move, but it might take a while. Using bleach will also help pull your pH up. So, in the future you will be trying to keep your ph down rather than up. Luckily, that's easy to do with muriatic acid.

Michael

I'm now officially a bleach convert. Just thought I'd post my numbers throughout the opening of the pool. The pool is sparkling clean now. I don't know if this will help anyone else with a big pool or not. Thanks again to everyone for their help in this conversion. :D

I only had enough stuff to test CYA once. CYA was 100 on 4/15/06. I'm waiting on the new kit.

4/14/06 PM FC-0 CC-0 TC-0 pH-?? Alk-?? Took pool cover off. Added 5 lbs. of dy-chlor II and loaded skimmers with 3' tabs.

4/15/06 PM FC-3 CC-0 TC-3 pH-6.8 Alk-40 CYA-100 Added 4 gallons of bleach. 1 box borax.

4/16/06 PM FC-13 CC-0 TC-13 pH-6.8 Alk-50 Added 1 box borax.

4/17/06 AM FC-10 CC-0 TC-10 pH-6.8 Alk-50 Added 2 gallon bleach. 1 box borax.

4/17/06 PM FC-11 CC-0 TC-11 pH-6.8 Alk-50 Swept to waste. Added 1 gallon bleach. 2 boxes borax.

4/18/06 AM FC-12 CC-0 TC-12 pH-7 Alk-40

4/18/06 PM FC-12 CC-0 TC-12 pH-7 Alk-40 Added 2 gallons bleach. 1 box borax.

4/19/06 AM FC-12 CC-0 TC-12 pH-7.2 Alk-30

4/19/06 PM FC-14 CC-0 TC-12 pH-7.2 Alk-30 Added 2 boxes borax. 2 boxes baking soda.

4/19/06 PM2 FC-14 CC-0 TC-14 pH-7.2 Alk-100 Swept to waste.

4/20/06 AM FC-14 CC-0 TC-14 pH-7.4 Alk-100


Times:
AM - 7:00am
PM - 4:30pm
PM2 - 7:00pm

Boxes are = 4lbs.

THANKS AGAIN!!!

How big was your box of baking soda. I'm very surprised you went from 30 to 100 with only two boxes of baking soda in such a big pool. Mine usually takes 15 pounds on startup.

They are 4lbs boxes. I was surprised also. I don't know if all the other chemical "magic" impacts the Alk level or not.

Borax will raise your alk too, but to a lesser degree. Alk also tracks along with pH. So, as your pH rises, so does your alk. Good work though!

Michael