Or too much sand is in the filter so not getting the buffer needed from the top of the sand or the mpv is being moved too early before the sand settles when the pump is shut off for repositioning of the mpv handle.
Yes you do to shock pools at TFP. It's part of the slam.
Which that link you left didn't give me any information about slam, it just redirects to the TFP home page BTW.
And if you don't shock pool water here (which you do), and we're not allowed to post about the process of shocking pools, then someone should post that in the forum rules for us neanderthals that kill algae with road flares and machinguns.
To shock is a verb, an act, or action, a process mainly used to break up Combined Chlorine by raising your chlorine level, as well to kill algae, bacteria, viruses, and germs. CC needs to fall to zero during slam right? Like in the act of shocking!
You see you've been shocking your water, as to the extent of how hard you shock the water is up to you, and whatever process you want to use. I was very clear to leave that up to the the OP, while not stepping on any toes here by reframing on suggesting how hard, or lite to shock a green pool... I said to shock it. Period.
Don't mis read my use of the term shock with marketing terms, products, labels, monkeying around etc. That verb has been around for decades. Read it for what it means.. To shock.
By the way we have anything else to ad to the OP problems besides my decades old terminology?
I figure your pool to be about 7600gallons. So to put 5ppm of FC in there, while waiting for your test kit, add 49 ounces of 10% liquid chlorine to get you there from zero ppm FC.
Do this daily and mix it in good until you get the test kit you ordered. Once that arrives we're going to want you to run all the tests and list them here like this:
salt if applicable
JamesW will help you figure out your sand filter in the mean time.
Late update, but I unfortunately had a busy week being hit by Hurricane Ida followed by being away for the holiday weekend. I had my test kit waiting for me on Monday, and I replaced the sand in my sand filter earlier today.