Would think it wouldn't be too costly to have a truck full of seawater delivered to your storage tanks / pool. Seems to me some pools use salt to prevent algae.
Hell even in CA the envrios should see this as combating climate change and sea levels rising
Temp sprinklers on the roof. Simple, effective and low cost. KISS.
Still need a pump and storage. That guy above using a 5# propane cylinder seems comical. Wet things once, out of gas. Piss around and swap fuels...still having to store petrol. Hopefully not burning alive when the heat of the fire quickly drys whatever he covered.
Petro has more energy per volume, trade off is you need to run the system regularly. If I was to stay behind on a fire, I really need that equipment working. IMO the added hassle of a quick monthly test would be worth the added run time & knowlage the system is in working condition. Already have several things that need it anyway and do the same. Snowblower, lawn mower, chainsaw, etc. Additives and monthly 5min run, it just works. In the rare case it doesn't, not under pressure to get it back in service.
Don't really mind storing it at home either. Have smoke / heat detectors all over and its far from the bedrooms as it could be. If the house does burn, getting out isn't an concern. Storing a fair bit, hopefully make sure the home is a total loss before the FD can arrive. Much rather deal with total loss than fix something you can never get that smell out of. Was in a school that burned and first visit I could smell a fire like it happened yesterday. Asked about it and was told the building had a fire some 15+yrs earlier and they repaired it. No thanks. Get out first, call the fire department last. When they arrive, tell them there your a prepper/welder and loads of fuel and ammo in there LOL.
Burns to ashes, think of the money saved in debris removal alone.