I'm not clear what tub you're referring to here, the shower tray, the exchanger tray or a bath tub.
As a permanent fixture it doesnt sound counterflow. As a temp lashup it sounds more work than 4 bits of microbore bent into a spiral with a manifold at each end, plus the parts cant be reused in the final finished item.
ISTR space was limited, so introducing a bathtub may not be the best option.
NT
The original post didn't appear on my server so I'll respond here...
|| I have a ski cabin with a 60 gal water heater. There are two || showers. This house was built originally for a couple, but when I || use it I have as many as 14 guests stay at a time during ski || season. Even if people take quick military showers, when you get || to the last few people they end up with cold showers. Not sure if || this is due to the heater capacity, or if due to the mountain cold || water (probably just above freezing) that is flowing in to the || tank. To make maters worse, this heater runs off slow burning || propane and is at high altitude - seems to take anywhere from 2-4 || hours for the tank to get hot even at max temperature setting. || || There is not a lot of room anywhere to put a second tank, so... || ... Has anyone tried putting a on demand system between the water || main and the input to a conventional heater such that the incoming || water || is much warmer ?
I haven't; but since the thread has already wandered off into a discussion of heat exchangers, why not borrow from warm-climate sailing where water is solar heated in a black plastic bag for on-deck group showers. It makes a small amount of hot water go a long way (a gallon and a half or so per person).
Try to save a bit of hot water from the group shower(s) for any self-conscious types who value privacy more than warmth. :-)
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA
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