S9 Water Tank

My S9 tank runs dry after about 7 hours of use. I want to adjust it to allow it to still have water in it up to 9 hours but can not. The owners manual says the screen should show the symbot and a number like 3.5 that is adjustable up and down. My machine number reads 60 and is adjustable upwards above 60.

The 60 is heated hose air temp.
Take the hose off the machine and it should only give you a humidity selection choice....that's the easiest way.

I have used my s9 on "auto", which allows hose and tank heater to be adjusted independently.
If I remember correctly, the setting is in the clinical menu.
I switched it back after a couple of nights--easier on auto.
You can "swap ends" on the heated hose, plugging the mask end to the machine.
This turns the heated hose into a non-heated hose.
--with the bump near your mask, but not hooked up.
The s9 on auto aims to raise the humidity to ~ 80-something.
Adding humidity to the ROOM will reduce the cpap's effort to evaporate enough water.
The s9 tank will only hold 14 oz, but you can put more in a room humidifier.

I had this issue too.

My "tank" ran dry after about 6 hours sleep here in Toronto.

I added a humidifier to my furnace; this was to protect musical instruments, not me. One cracked due to low humidity.

Problem solved. My S9E humidifier has never run out since.