Northeastern US spring opening: TC 10 - FC 0....time for a tennis court?

[RobKM75]

Please help. After performing the typical opening procedure and then shocking per bioguard dealer instructions, I have some ugly TC numbers. The pool is crystal clear, but not balanced.
Here are the details:
35,000 gal. DE filter

CYA 30
FC 0
TC 10
pH 7.4
ALK 200
CAL 225

Specifically, I dumped 18 gallons of 10% liquid chlorine and 12 lbs of 99% dichloro on Bioguard dealer recommendation and ended up here.
help...

 

[needsajet]

Welcome to TFP! Good to have you here

Commonly, high combined chlorine and no free chlorine indicates the presence of ammonia. It can usually be eliminated with repeated additions of chlorinating liquid (not solid or powder) but not quite as much at once. What test kit are you using?

Here's a primer on the pool care method used here at TFP: TFPC for Beginners

 

[RobKM75]

Bioguard Test Kit. i order the Taylor kit. Why liquid? I was recently recommended 73% calcium hypochlorite. I was also told that it is an "all or nothing" process. If I dont put enough the first time...I will be back to square one. They told me to use 25 lbs!

 

[needsajet]

K, good. The Taylor K-2006C is the one to get for doing TFPC.

Trichlor and dichlor both add CYA as well as chlorine, which you don't need any more of right now (you had 30 ppm CYA and added 20 ppm by way of the dichlor). CalHypo adds calcium as well as chlorine, and a certain amount of calcium is fine. I don't think 25 lbs would hurt your calcium level in the long run. If that's the most convenient for you, then yep, that's fine, but liquid doesn't add any, so you don't have to concern yourself with calcium, so that's more convenient for many people.

As long as there's not an ongoing source of ammonia, it won't matter how quickly it's done. A certain amount of FC will convert a certain amount of ammonia to combined chlorine, which will then burn off in the sun. If it were mine, I'd add enough chlorinating liquid to get to 10 ppm FC, and then check it an hour later. I'd top up to get it back to 10, and keep repeating that until it holds.

A common source of ammonia on opening is after CYA has been eaten by CYA-eating bacteria. When that happens, you usually get 0 ppm CYA on opening, but you have 30 ppm CYA, so I'm not sure where the ammonia is coming from. Sometimes it's garden runoff or blown-in fertilizer. Sometimes it's very heavy urination with low free chlorine, which could be from swimmers or animals.

Just to rule something else out, has bromine ever been used in the pool, or algaecides based on sodium bromide?

 

[RobKM75]

No bromides, just copper based algaecide. 25 lbs isnt a ridiculous amount of chlorine?

 

[GOONiE]

No bromides, just copper based algaecide. 25 lbs isnt a ridiculous amount of chlorine?

not for a slam... but LC is much cheaper than powder chlorine and doesn't add any cya or calcium.

 

[needsajet]

Check out PoolMath to see "Effects of Adding Chemicals".

I get 62 ppm FC and 44 ppm CH. So that would be enough to raise it to 10 ppm FC six times.

Your starting point is 225 ppm CH, so the extra CH won't hurt. If you were in the southwest I'd be concerned, but your summer rains likely dilute your CH over time anyway.

Best to stop using any copper-based algaecides because those introduce the risk of copper staining and/or turning hair and fingernails green. They can also kill algae which can mask a lack of adequate chlorine for sanitation. We use algae as a warning sign that sanitation is inadequate, and TFPC prevents algae by using the correct chlorine level relative to the CYA level.

 

[RobKM75]

So how much liquid chlorine (10%) would you recommend to get the pool from TC10, FC0 to get it back where it should be?

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and why is the pool crystal clear!?

 

[GOONiE]

224oz of 10% to get to FC of 5.

it's clear because you're lucky

 

[RobKM75]

But I read that you must bust the demand and go 10x CC? The calculator says I need 35 gallons of liquid chlorine to achieve that. Thoughts?

 

[needsajet]

No, just raise it to 10 ppm FC and re-test an hour later. If it's zero, add 10 again. As it starts to hold, you'll be topping up, and then within a repeat or two it will hold for an hour. Then we can plan the next steps.

If your home test kit doesn't go to 10 (say it goes to 5), because you don't yet have your K-2006C or TF100 test kit, just dilute your sample 50/50 with tap water and make sure it still looks like the full 5 ppm FC. Ideally, put the tap water you're going to be using for diluting in the sun for an hour to wipe out the FC that you get in the tap water.

Ammonia in the water doesn't make it un-clear. Pools get cloudy for a bunch of reasons, but ammonia isn't one of them.

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Each addition of FC knocks out some ammonia. It doesn't come back unless CYA-eating bacteria is eating CYA and turning it into ammonia, or incoming ammonia from something.