Yeah, i didn't make it easy for myself, but then again if i had dropped $500 and bought a minigen, it would be running for its life right now in my room. With all the HVAC shit running i can lose 3000ppm concentration pretty fast.
Hey man im not far from you, dealing with the same desert environment, fucking 100+ out today again. Im also in a spare bedroom. Do you use a mini split also?
The water heater co2 deal isn't too tricky, just a 4" flex-hose from the exhaust of the WH, routed to the grow room 30+ft away. I only need to an 80mm 12v PC fan, loosely placed into the 4" flex-hose to suck in thousands of ppm worth of CO2 in minutes, one WH run cycle, one shower basically. But only when the WH is running. When its not running what it sucks in from just the pilot light burning isn't enough to raise the CO2 level much above ambient.
I need to find a way to have the fan kick on when the burner in the WH fires up, and have it stop when it goes out, and or when X level CO2 is reached. Also have the room more sealed so when its filled, it stays.