Salt Level Keeps High without Addition of Any Salt

[waterbear]

"Losing chlorine does not cause you to lose salt"...

Well, when the electrolysis process separate sodium chloride (salt) into sodium ions and chlorine gas, if you don't contain the gas, it will evaporate into the air.

And once it's gone, you just don't have enough chlorine to combine with sodium ions to form salt again.

This is called the law of conservation of mass and don't try to challenge it.

The point you are missing is that the chlorine generated forms hypochorous acid and hypochlorite ion and does not exist as chlorine gas so to speak. In fact, elemental chlorine cannot exist in water if the ph is above 7.0. Normal pool pH is higher than that and salt pools are usually at the high end of acceptable because of increased outgassing of CO2 because of aeration from hydrogen gas generation at the cathode. Outgassing of CO2 is the main cause of pH rise in salt pools (and any pool that uses unstabilized chlorine sources in fact, exclusive of new, curing plaster) and the rate of outgassing is directly influenced by the TA, which is why low TA is beneficial in a salt pool. Also, in a salt pool CYA also indirectly helps with pH control since higher CYA levels allow for lower cell output which means less aeration which means less outgassing of CO2. Emperical evidence indicates that maintaining the FC at 5% of the CYA seems to be optimum, btw.
Under practical conditions in a salt pool salt is lost by water replacement. Period.
Your understanding of the chemistry of a salt pool is a little off. The chlorine destroyed by sunlight does not gas off. Technically, we are discussing hypochlorous acid, hypochlorite ion, and chlorinated isocyanurates (when stabilizer is present) When these are destroyed by UV light they revert back to chloride ions and mass is preserved. CYA does NOTHING to contain chlorine gas and chlorine gas, per se, does not exist in the water. Even when a gas chlorinator tech treats a pool by bubbling chlorine gas into the water it forms (once again) hyoochloruous acid, hypochlorite ions, and chlorinated isocyanurates.

Any other questions?

Mods: since this is getting technical perhaps it should be moved to the China Shop.