Am I Using Pool Math Right?

[kikiganz]

We are using Pool Math to bring our chlorine up but I am concerned I am not using it right? For our CYA and pool size it says our goal FC level is 6. This morning we were at 0 TC and it said to add 92 ounces of 10% Liquid Chlorine to get to 6. We did but it only got us up to 1. So we entered 1 and it is now telling us to add 77 ounces of 10% liquid chlorine. Does that seem right? I am reading others posts about adding "6 jugs" and still working to get it up so I am wondering if I am doing something wrong?

Thanks for your help!
KG

FC: 1
PH: 7.2
CH: 250ppm
TA:60
CYA:85

 

[cowboycasey]

that is exactly what I got when I input your data

How does your water look? is this a fresh fill.. you may have something in the water it could be used up fast..

Let us know

 

[Richard320]

You're using poolmath correctly, but something doesn't compute.

People adding jugs and jugs are trying to get to shock level, often in the 30s. And they may have a much larger pool. If your pool is truly only 12,000 gallons, then you should be seeing the doses poolmath is telling you. But you should also be seeing some results. If you added 6 FC this morning and you're down to 1 FC now, that's a lot! About double what I'd expect to see.

So... perhaps your pool is larger than you think. My pool is basically a 12 X 32 kidney and 3 to 8 feet deep and it holds 16000 gallons. Second, the 10% bleach could be old and weak. Third: you have something growing in the water that's using your bleach.

How does the water look? Is it clear? Can you easily see the drain in the deep end? Any patches of algae?

The bleach: do you still have the cardboard boxes? It should have a date code somewhere. Do the boxes look old and shelf-worn, like they've been sitting out in the patio section at Lowes since last year?

You might just have to run an Overnight Chlorine Loss Test to determine just how high the bleach is taking the FC in reality and how much you're losing. Calculate the dose to get to 10 or so, maybe a jug and a half. Let it circulate for at least an hour while you make a lap around the pool with the pool brush to really get some cross-currents going. It's like stirring milk into your coffee, just on a gigantic scale.

After the sun stops shining on the pool, go test the FC. Remember that number. Set your alarm clock and get up and let the water circulate again and then test FC before the sun hits the water. If you lost more than 1 FC overnight, you have a problem. Only two things destroy FC: UV/sunlight and organic matter. Since you've eliminated light, it will have to be matter.

 

[kikiganz]

Pool is crystal clear. Couldn't expect it to look any better. We do notice a couple of algae patches on the wall...they seem to be wherever the plaster is compromised or worn but truly you only see them if you search. They are hard to notice.

A couple of questions...

First, you said:

If you added 6 FC this morning and you're down to 1 FC now, that's a lot! About double what I'd expect to see.

I don't know what you mean when you say I "added 6 FC this morning"? Do you mean I added to get to 6FC? And the part about "down to 1 FC...that's about double what I would expect to see." I don't know what you mean by that because we were at 0, added the chlorine, and are up to (not down) 1. I just expected to be up higher than that. This is all new to us so we are still trying to learn the language so sorry for the need for further explanation.

Important note, hubs said he only added about 65 ounces instead of the 92 recommended this morning because we read on here that people cautioned you can always add more but it's hard to take away. But still, I would expect it to get us higher than to just 1 if we did 2/3 of the recommended dose right?

The bleach date is March 23 of this year so I don't think that is the problem????

Now about pool size. You may be onto something with that which we had not thought about. Previous owners never told us our size. Pool store had it in their file somewhere but we have no idea where they got it from. Maybe it is off? We have a free form pool (similar to a kidney but with an extra curve) that goes from about 3'-6' deep. It is 14.5' at it's widest point and 32' long (only know this because we just purchased a solar cover). Maybe we need to make sure we have the right size before we do anything????

Any other suggestions are appreciated. Thanks!
KG

 

[Richard320]

Hmmm... crunching numbers... if the pool is 16000 gallons and you added 65 oz, that would add 3.2 FC. If you were at 0, you went up to 3.2 and are now down to 1, that's only 2.2 FC loss all day, which is decent.

Pool is crystal clear. Couldn't expect it to look any better. We do notice a couple of algae patches on the wall...they seem to be wherever the plaster is compromised or worn but truly you only see them if you search. They are hard to notice.

A couple of questions...

First, you said:


I don't know what you mean when you say I "added 6 FC this morning"? Do you mean I added to get to 6FC? And the part about "down to 1 FC...that's about double what I would expect to see." I don't know what you mean by that because we were at 0, added the chlorine, and are up to (not down) 1. I just expected to be up higher than that. This is all new to us so we are still trying to learn the language so sorry for the need for further explanation.

In the original post you started at zero and targeted 6 to get the 92 ounce dose. Assuming the bleach is full strength and the pool is only 12000 gallons, you added 6 and lost 5 during the day which leaves you with a net gain of only 1. Remember, chlorine disappears every day. Unlike CYA that sticks around, chlorine must be replenished daily. A loss of 5 would be excessive, which is why I questioned the other stuff.

Important note, hubs said he only added about 65 ounces instead of the 92 recommended this morning because we read on here that people cautioned you can always add more but it's hard to take away. But still, I would expect it to get us higher than to just 1 if we did 2/3 of the recommended dose right?

Yes, in a 12000 gallon pool, 65 ounces would add 4.2 FC instead of 6.

The bleach date is March 23 of this year so I don't think that is the problem????

No.

Now about pool size. You may be onto something with that which we had not thought about. Previous owners never told us our size. Pool store had it in their file somewhere but we have no idea where they got it from. Maybe it is off? We have a free form pool (similar to a kidney but with an extra curve) that goes from about 3'-6' deep. It is 14.5' at it's widest point and 32' long (only know this because we just purchased a solar cover). Maybe we need to make sure we have the right size before we do anything????

Any other suggestions are appreciated. Thanks!
KG

For sizing, keep close watch on how things affect the chemistry. You can use Effects of Adding Chemicals down at the bottom of poolmath to see. So... if you are always coming up short on the changes you should see, your pool is bigger than you think. If you target a certain pH and you add that much acid and you end up below what you targeted, your pool is smaller than you think. In either case, adjust the pool volume in poolmath up or down and see what happens. Eventually you will narrow it down to within a couple hundred gallons either way.

You do need to maintain much higher chlorine that you have been, especially with some algae patches. Minimum FC for 85 CYA is 7. Target should be more like 11 or 12, because you do have algae spots. Maintaining higher than minimum FC and daily brushing of those spots should eliminate them.

 

[kikiganz]

You have no idea how much you taught me in that single post! This is how much I wasn't understanding this pool stuff. I didn't realize adding the recommended chlorine dosage brought me to that level and then the level falls all day. I thought you added it, let it sit a while to ensure it fully disperses, and then measure and that is where you end up.

So now I have an idea of what I need to keep an eye on. One more question...I just got the TF-100 test kit. While I am trying to get everything up to normal levels, can I just use the daily chlorine test kit or do I need to do the advanced one with the powder until I get things back to normal and stabilized?

Thanks again!
KG

 

[cowboycasey]

with a CYA of 80 you will always use the FAS-DPD (the one with the powder) because the OTO (PH and Chlorine cylinder) can not go above 5fc and you need to be at a target of 8fc every day... you should start out at 11 or 12 FC like richard said above to stay ahead of an algae bloom for a couple weeks..

Trust me, all of the sudden it will be really easy KG

 

[kikiganz]

Thanks cowboycasey! In light of that, should I just drain more out to get my CYA down further or just be patient and let it drop over time? I assume swimming in a FC of 11 or 12 is ok? Also, do I need to test the other elements every day? Does the weird chlorine levels mess with them as well? Finally, I know my CH is low but someone said I can just ignore that "for now" while I get my chlorine under control. How long is "for now"?

Thanks!

 

[Mr Bruce]

Thanks cowboycasey! An light of that, should I just drain more out to get my CYA down further or just be patient and let it drop over time? I assume swimming in a FC of 11 or 12 is ok? Also, do I need to test the other elements every day? Does the weird chlorine levels mess with them as well? Finally, I know my CH is low but someone said I can just ignore that "for now" while I get my chlorine under control. How long is "for now"?

Thanks!

I would drain down to 50-60 CYA. Swimming at or below SLAM level is fine if the water is clear. You don't have to test everything everyday, I would recommend testing FC/CC and pH everyday for the first month, and then you can relax to every other day + pool use days. pH test is unreliable with FC greater than 10. Run a full test once a week. You are on the bottom end of CH range, but nothing drastic. Ice melt is hard to find in ATL this time of year I bet, might want to spring for the overpriced pool store variety or Lowes/HD version.

 

[kikiganz]

I had just bought the expensive stuff at the pool store before finding these boards so I have a brand new tub of it itching to be used. Should I go ahead and add some or wait for chlorine to get better?

Tested this morning and got
FC: 7
CC: .5
Ph: 7.2-7.5

Stupid question but I have the TF-100 test kit. The only way you test pH with it is with the basic kit where you compare the shades of orange right? I ask because today I couldn't get an exact match. It was a little darker than 7.2 and a little lighter than 7.5.

So do I now want to get my FC up to 9?

Thanks,
KG

 

[kikiganz]

My husband just had me do the math on what it would cost to replace about 40% of the water again. We had no idea it would be so cheap???? We were expecting $500+ but it looks like it is only going to be about $100. So I think we are going to drain again in the hopes of getting it down to normal range????

We are curious how our CYA got so high in the first place so that we can avoid this again in the future? Anybody know? We did the Vitamin C treatment for the metals. After a few weeks the *!$%* at the pool store told us to shock it to get the chlorine back up. As you guys probable know within about 6 hours we had a swamp. We used Metal Free and cellulose in our sand filter for two days and got it looking good again. Did any of that cause the high CYA?

Also, anything we need to ensure we are doing before, during and after the drain?

Thanks,
KG

 

[Texas Splash]

We are curious how our CYA got so high in the first place so that we can avoid this again in the future?

Good morning. CYA increases from the stabilizer we either add to the water on purpose or as a by-product from something else. The most common culprits are chlorine tablets (pucks) and pool store "bags-of-shock". Once you lower CYA via water exchange, the CYA will never climb again unless YOU want it to as long as you stick to the TFP recommended chemicals. Yeah ... the pool store said ....... we know.