This year I'm part of a group bringing some art that incorporates flame effects to the playa. We are currently having issues with our propane tanks cooling off after about an hour of use and then our fireballs don't have any pressure behind them anymore

We've got six 100 lb tanks so we'll need a decently large tub. Then I'll be looking for an outdoor on demand water heater, a pump to cycle the water and a temperature sensor setup to switch the heater off if the water gets too hot so we don't vent the tanks.
I've got a few questions but also happy to receive any advice from someone who has done this before. I'm looking for those tips to save time and headaches out on the playa!
Any advice on a good kind of on demand water heater to use? I'm not sure how much capacity I'll need both for heat and flow.
Also worried about clogging either the pump or the heater with playa dust that gets in the water. Any experience with this?
How much water do you need around the tanks? How high do you fill the tub?
Like I said any advice will be greatly appreciated!