I'd be curious to hear about everyone's experience with chlorination strategies to figure out what would work best for me. For many years, I've been using trichlor pucks along with calhypo for shock with mixed success. It's been pretty painful to deal with the high levels of CYA and the calcium deposits that have been around the tiles (I'm in the process of painfully cleaning all of those ugly marks out). I've been looking at liquid chlorine as an alternative since it's been highly recommended here in the forums, but it all comes down to what's most cost effective in the end. For my area, The best price (when not on sale) I could find per concentration is as follows:

Chlorine type | Cost / unit | Unit cost | Amount to raise 10k pool by 1ppm | Cost to increase 10k pool by 1ppm |
---|---|---|---|---|

trichlor (90%) | $145/50lbs | $0.18125/oz (weight) | 1.5oz (weight) | $0.27 |

calhypo (73%) | $180/50lbs | $0.225/oz (weight) | 1.8oz (weight) | $0.41 |

liquid chlorine (10%) | $13/3gallons | $0.034/oz | 12oz | $0.41 |

For every 1ppm of chlorine added, I understand that there's the following negative effect from each chemicals:

Chlorine type | TDS per ppm of chlorine | CYA per ppm of chlorine | Calcium Hardness per ppm of chlorine | pH |
---|---|---|---|---|

trichlor (90%) | +1.4ppm | +0.6ppm | 3 | |

calhypo (73%) | +1.2ppm | +0.7ppm | 10.8 | |

liquid chlorine (10%) | +1.6ppm | 13 |

Now turning my attention to the effect of pH first. When used together, trichlor and calhypo tend to have their pH cancel each other out so I'm ignoring the cost of balancing the pH for that combination. It's not quite true of course but to simplify the calculations, I'm making that assumption. As for liquid chlorine however, according to my math, it would require roughly 12oz of muriatic acid to compensate for the negative effect of the ph caused by liquid chlorine. So looking at my options here:

Acid type | Cost / unit | Unit cost | Amount to lower 10k from 7.6 to 7.5 | Cost to lower 10k from 7.6 to 7.5 |
---|---|---|---|---|

Muriatic Acid (14.5%) | $11/2gallons | $0.043/oz | 8.3oz | $0.36 |

Sodium Bisulfate (93%) | $52/25lbs | $0.13/oz (weight) | 5.1oz (weight) | $0.66 |

It seems like the clear winer is muriatic acid here at a lower cost and lower TDS. If this is true; the true cost of using liquid chlorine to raise by 1ppm basically rises by roughly $0.688 (16x0.043) for a total of $1.10/ppm.

Finally, I turn my attention to the water refills required to remove the extra 'junk' added to the pool. That one's a little trickier to calculate due to the seasonality of the chlorine demand unfortunately. I turn my attention to the CYA only given that it's the most damanging and least tolerant of all of them. TDS has a generally high tolerance of 1.5k while CYA has a nasty relationship where the higher it is, the more you need and thus the more you end up adding of it. Water costs are quite high where I am. It's at $6.55/CCF or $0.0087627 per gallons.

I'm assuming that the CYA will start at 30 and that the pool will be halved when it reaches 60. I'm ignoring the effect of higher levels of CYA in terms of demand for the sake of keeping things simple for now. It will take a total of 50ppm increases to increase the CYA to 60 at which points it would cost $43.81 to refill a 10k pool or $0.8762/ppm. Bringing the total cost for trichlor to at least $1.1462/ppm. Now if we look at the effect the demand over time since the CYA is increasing and requiring us to put in my ppm of chlorine after every addition

Liquid chlorine will also require a refill due to TDS at some point. Playing the same game and allowing a range of 750-1500 TDS before a refill indicates that it will require ~469ppm to raise the level by 750. By the same prior logic, we have $0.093/ppm. Bringing the total to rougly $1.193/ppm.

On the surface it seems slightly more expensive to go down the liquid path, but if I undo the assumption that the CYA has no effect on ppm demand for effectiveness the story changes. And add that we want to keep the effectiness of the chlorine throughout the CYA addition, we would actually need to change the water after adding 50ppm in the equivalent of 36ppm of liquid chlorine (obtained by modeling chlorine intake assumign a start point of 2.25 @ CYA-30 and with a FC demand equal to 7.5% CYA). Meaning that the net cost of trichlor is 1.39times more expensive or averaged at $1.52/ppm which is clearly higher than the liquid alternative.

Of course the cost structure here is a function of my local economy and the cost of things in my area. I'd love to hear if anyone else did the analysis for their region and figured out if the math works out. Feel free to point out areas where I may have made a mistake or wrong assumption.