ORP + pH Sensor + Acid pump - Optimum CYA levels .. or zero CYA?

[trbvm]

Today, the PB and an official Hayward tech hooked up the Hayward Sense & Dispense system that has the ORP & pH sensor.
We also hooked up the Stenner pump that is dispensing a diluted 2:1 ratio (2 H2O + 1 Acid) of 31.45 baume Muriatic acid.

So, prior to configuring these, I had balanced the water to 7.5 pH, 5 FC, 0 CC, etc.

The (awesome) tech from Hayward then spent a lot of time to configure the system.
The system has been running for 3-4 hours now and I am seeing a constant 7.5 pH and 5 FC

Upon reading extensively on the topic, there were topics that say that an ORP + pH system works well with a CYA level of ZERO!

To the non-chem-geek like me, if we are constantly dosing the pool with acid trickles and SWG chlorine, albeit, in small amounts, why do we need CYA?

In my new pool, I have 55 CYA and hope to keep it at that level, but is it beneficial to allow the CYA to come down in the future?

 

[jblizzle]

Because the summer sun will destroy the FC faster than the SWG can make it. Or if the SWG can keep up, it is working much much harder and shortening the life of cell.

 

[chem geek]

The active chlorine at the minimum FC/CYA ratio we recommend is equivalent to only 0.06 ppm FC with no CYA. You can't maintain that low an FC in your pool unless you have absolutely outstanding circulation and fast turnovers. There simply isn't enough chlorine around to handle any unusual events in the pool. The purpose of the CYA is not only to protect chlorine degradation from sunlight, but to enable having a reserve of chlorine while significantly moderating chlorine's strength.