Chemistry advice

[liphil]

Received tf-100 kit today and first results assuming I did everything correctly.

C = 0
pH = 7.5
TA = 120 (turned a light shade of red at 110 then darkest it went was at 120)
CYA = 0

I've filled the pool to about the top of the skimmers so I can manually vacuum to waste when my hose arrives today. There's a fair amount of dirt at the bottom so I assume I should by pass the filter. Should I recheck levels after vacuuming water down to normal level or won't it mater. Filter had been running for about 4 hrs when I took sample so water should have been well mixed.

Thanks
Phil

 

[woodyp]

No need to retest. Just get you some FC and some CYA in there.

 

[YippeeSkippy]

Did you also test for CCs? Go ahead and do the CH test too...you never know. It will give you a reference.

Are you adding chlorine and CYA?

Yip

 

[liphil]

Should I get CYA levels up first?

 

[YippeeSkippy]

You can do these both about the same time.. Get the CYA into a sock in the skimmer (keep pump running) and then start pouring the bleach into the pool in front of a return. Repeat as necessary based on testing.

Yip

 

[liphil]

When I did the chlorine drop test the water was never anything but clear from start to finish so I assume I have no CC.
CH = 175
Havent looked yet but what is the recommended CYA to use?

 

[liphil]

So looking at pool math with a 28100 gal pool with a cya of 0 I need to add a little over 9 lbs of granulated cya to obtain a goal of 40? Can yo get 9 pounds of that stuff in a sock?

 

[YippeeSkippy]

No, but you can put two socks in, and start slow. Go for 5 or 6 pounds...retest... then add more if needed.

You always want to go easy and not overdose that because CYA doesn't go away easily.

So one or two socks filled.... you can also hang them over the side of the pool in front of a return, or hang on a floating noodle etc. You just don't want it sitting against the side of the pool on the surface. Its too acidic and could bleach it.

Yip

 

[liphil]

Last night after adding the 3.5 gallons of 10% chlorine after adding about half of the 9 lbs 8 oz of CYA I did a round of tests just to see where I was at. These were the resulsts:

FC: 20
CC: 0 ( at most the sample turned the slightest ting of light pink but I was really straining to see it)
TA: 100
pH: 7.6
CH: 175
CYA: <20

I found the FC number alarming seeing as how it was almost double the number of 12 I was shooting for. However I figured lets see what happens in the moring. Left two socks with some CYA in skimmers vacuumed and brushed pool. This morning , about 10 am, there was still quite a bit of CYA in socks so I'm estimating that I added somewhere between 6 and 7 pounds so far. I checked the levels at this point and the results:
FC: 16.5
CC: 0
CYA: 45?

I assume that the FC came down due to burn off seeing as how there are no CC and the water temp is probably to low for any algae to be present (55 degrees). I have been running filter the whole time. A few questions.

1.) Do I even need to be slamming pool being that the water temp is below 60 and there are no CC?
2.) Am I testing CYA, FC, too soon after adding it and that's why my numbers are way off from pool math?
3.) How finicky is this CYA test? Looking on line it seems like you could get a lot of different readings depending on temp, light amount and angle.

Other than that the water is looking good. Looks pretty clear during the day but at night when I put the underwater light on it looks somewhat more cloudy and can see small debris floating around. Is this due to having a sand filter that just doesn't get the small stuff?

Thanks,
Phil

 

[Mr Bruce]

1) Sounds like you don't need to be SLAMming the pool. If it's clear (crystal clear, can tell if a quarter is heads or tails in the deep end clear) you are probably fine. Most of us can drive ourselves crazy looking at the "floaters" at night with the pool light.

2) Let the CYA dissolve completely and test the day after. Give the socks a squeeze to help them along. FC, on the other hand, should be dead on after adding and letting the pump run 30-60 minutes. If it's way off, there is a problem with your estimated pool size or chlorine/bleach strength.

e: If you tested CYA at >40 I would pull the socks now so that you don't overshoot. Test again tomorrow if conditions are good.

3) Very. The key to the CYA test is to do it in full sunlight, with your back to the sun, hold the tube waist high with 2 fingers (yes I know it sounds like voodoo) pinching at the top. You are trying to get as much ambient light into the tube as you can. The test is really +/-15 anyway, just do it 2-3 times by pouring the solution back into the squirt bottle again and averaging what you get.

 

[liphil]

Thanks for the quick reply. So with my back to the sun the tube itself will be in the shade and not in direct sunlight?
My measurements may be off. the pool is 18 X 36 but the depth is hard to figure. it's 4' at shallow end and 7' 7" at deepest but the walls at deep end dont go straight down to bottom, they start slanting in 3 ft down. So the formula might not account for that giving me smaller volume than I thought.

 

[Mr Bruce]

Yes. You want it bright all around you, but no sunlight straight into the tube.

The chemistry is a better calculator than our estimates. Over the years I have lowered my personal estimate from 40k to 32k based on chemistry alone. PoolMath is spot on.

 

[Captain 776]

A sock seems to be the preferred method here but I prefer to put it in a 5 gal bucket and stir it........CYA does NOT readily dissolve in water, so stir it, then dump off the milky white water, then fill the bucket again. I would only put 1-2 pounds in a bucket at a time.
I have dissolved 3 pounds in about 6 hrs, just do as I said above. After u dump off the milk, fill bucket, stir, let it sit an hour or so, stir again, dump it off.
another thing I do, is I use a paint stirrer in my electric drill, this is way faster than the sock method and no you won't get 9 pounds in a sock.
maybe if u get queen size panty hose, you may have a shot but it will take forever to dissolve.