Chlorine and PH readings

[bxb21]

I'm having some trouble getting my pool adjusted since opening it a couple of weeks ago. A week ago my readings were:
PH - 7.6
TA - 180
FC - 1.5
TC - 3.3

Two days ago I shocked the pool used about 5 pounds of shock and had no change in my chlorine numbers. I started aerating yesterday and I shocked the pool again, this time using about 3 pounds of shock, still no change.
My readings as of this morning
PH - 6.9
TA - 130
FC - about .5 - 1.0
TC - between 3.0 -4.0

The first readings were done at a pool store, the ones from this morning were done my me with my test kit. The aeration may not be adaquate since I'm using a pool cover pump attached to a hose and noozle with is producing a slow stream of water into the pool. I'm also running the return used for the vacumn which is causing a ripple effect.

Any help with what I'm doing wrong would be appreciated.

[bxb21]

Just to elaborate a little more, I have a plaster pool, 21,000 gal. I guess my questions are should I raise the PH first or shock the pool again? If I shock the pool again how much shock should I use to chlorine readings to change? I don't see any sign of algae, but I did have a bad case of mustard algae last year.

[KurtV]

I'm having some trouble getting my pool adjusted since opening it a couple of weeks ago. A week ago my readings were:
PH - 7.6
TA - 180
FC - 1.5
TC - 3.3

Two days ago I shocked the pool used about 5 pounds of shock and had no change in my chlorine numbers. I started aerating yesterday and I shocked the pool again, this time using about 3 pounds of shock, still no change.
My readings as of this morning
PH - 6.9
TA - 130
FC - about .5 - 1.0
TC - between 3.0 -4.0

The first readings were done at a pool store, the ones from this morning were done my me with my test kit. The aeration may not be adaquate since I'm using a pool cover pump attached to a hose and noozle with is producing a slow stream of water into the pool. I'm also running the return used for the vacumn which is causing a ripple effect.

Any help with what I'm doing wrong would be appreciated.
A few comments and questions for you.

The relatively high level of combined chlorine (TC-FC~4-1~3) is consuming the shock you're adding. What kind of shock are you using, by the way? Most people here just use ordinary, unscented laundry bleach.

What is your CYA (stabilizer) level? If it's very low or none, the sunlight is probably consuming your chlorine as well. If you post that number, you'll get advice on what level you need to bring your FC to to get rid of the combined chlorine. Alternatively, you can search the forum here for "Ben's Best Guess" table. That table will give you a shock level for your level of CYA.

Why are you aerating? Are you trying to lower your alkalinity?

Did you add muriatic or dry acid?

What kind of test kit are you using?

[bxb21]

The type of shock I'm using is Anthony/Sylvan Super Pool Treat. It says its 97% Sodium Dichloro-s-triazinetrione with 64% Available Chlorine.

My CYA as of last week was 135 ppm.

Last week my TA was 180, so I was going to add acid and then begn aerating, but it dropped to 130 and my PH dropped to about 6.9 without doing anything so I just started aerating to try to get my PH back up without raising the TA.

My first test reading were done by the pool store. The second reading was done with my test kits. I use one called Premier which uses the 1-5 bottles. I also a test kit called Pentair which allows me to test my FC and TC.

[Watermom]

PH - 6.9
TA - 130
FC - about .5 - 1.0
TC - between 3.0 -4.0

Oh boy. CYA of 135 is really high! Ideally, we suggest a cya reading of 30-50. Stop using dichlor. It adds more cya to your water. Instead, use plain, unscented bleach to shock with and for daily chlorination. You have two options for dealing with your high cya. One is to do a partial drain and then refill. The other is to live with the high cya and just run higher than normal chlorine readings. See the following link for the cl levels you would need to have for cya of 135. A cl reading of 3-4 isn't high enough to keep algae at bay in your pool. Also, if your ph doesn't go above 6.9 pretty soon, you should add a little Borax. You don't want a ph below 7.0 as it is acidic and can damage your pool and equipment. You might also want to consider buying the kit that most of us use from the sister site to this forum www.poolsolutions.com It will test everything you need and make it easier to maintain proper chemistry in your pool.

http://www.poolforum.com/pf2/showthread.php?t=365

[KurtV]

What she said.

Also, the di-chlor is probaby what drove your pH down so much. Try using bleach (sodium hypochlorite) instead to get your free chlorine level up; it will also help a bit to raise your pH.

[bxb21]

I don't really want to partially drain the pool, so I'll try to get my chlorine levels up. The chart says I need between 8-15 ppm with 25 ppm to shock.
That's a lot of chlorine, I assume it's safe to swim with it that high? Also will the CYA go down on it's own if I don't use any more di-chlor or will I be battling this every year unless I drain it?

I'll order the test kit today so that I can keep track of all this.

[duraleigh]

I don't really want to partially drain the pool, so I'll try to get my chlorine levels up. The chart says I need between 8-15 ppm with 25 ppm to shock. That'll work.


That's a lot of chlorine, I assume it's safe to swim with it that high? Your assumption is correct.


Also will the CYA go down on it's own if I don't use any more di-chlor or will I be battling this every year unless I drain it? It'll eventually go down....might take 'til next Spring.


I'll order the test kit today so that I can keep track of all this. That would be the smartest thing you can do for you and your pool! :) :)

[bxb21]

Since my last post I drained and refilled about a foot of water from my pool in hopes of lowering the CYA some. I won't know until my test kit arrives. I got the PH up to about 7.2 and the TA is down to about 110. Since Monday I've poured 17 gallons into the pool. Checked the reading this afternoon and its only about 1.0. I added 3 more gallons a few hours ago. When I first add the bleach the chlorine level goes up pretty high (my test kit only goes to 3.0, so I'm guessing somewhere between 6.0 and 8.0), then in a few hours it drops back to between 1-3. Is there some reason it keeps dropping or do I just have to keep pouring in the bleach?