Neighbours pool

I'm looking after a neighbours pool.

Pool Size 16x32
Vinyl Liner
Sand Filter
No Heater
Kreepy Crawler vacuum
Hayward Chlorinator (pucks)

Water appearance looks great
pH =7.4
FC = 6
TC = 6
TA = 120
CH=200
CYA=40

When I fill the chlorinator about half full, I need to turn the dial down to zero to prevent the pool from being overchlorinated. The chlorine readings with the dial at zero are 6ppm. She is using pucks about 1" diameter, and 1" long.

I'm not familiar with puck chlorinators as we have an SWG, but I don't think this seems right.

Sometimes the opening to the pool returns from the chlorinator doesn't close all the way, even with the chlorinator at zero. My inline chlorinator is a Rainbow 320 (I think made by Hayward), and when I use it, it still will introduce some chlorine into the pool with it set at zero. When I'm trying to up my CYA (which is frequently), I leave mine set at just below "1", and it keeps my Cl level at about 4 in an 18 x 36 pool.

I'm really surprised that the CYA is only 40 if she's using trichlor--but if those numbers are true, you can't ask for anything better!!

Janet