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
There is not a lot of room anywhere to put a second tank, so
What are my options to enhance capacity ?
I've heard that the on demand systems have flow problems. 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 ?
Tend to use this cabin on the order of 30-40 days during the Winter
when this is a problem. When the house is empty we turn the heat down
to bare minimum. So energy cost is not a super big concern -- main
issue is I want people to be able to take a nice hot shower after a
long day skiing.
Any other ideas or comments appreciated, or if you can point me to some
existing threads which cover this topic, I'd really appreciate it.
I have the exact same situation but have a 75 gallon tank (also propane
I just make sure I get to the shower first. :)
The killer is that the cold water is ~40.......so you use 2 gallons of
hot to 1 gallon of cold.
If I want to use the tub I've got to start fiilling it with all hot
water & finish off with tempid.
I checked into a demand water heaters (Bosc & Taguchi) but both the mfr
reps said that at high altitude the perfromance really drops off.
They said that a tankless wouldn't handle the whole house but if it was
hooked up to a single shower it "might" work. Plus you've got to
consider the instantaneous btu delivery capacity of your propane tank &
So really your only choice is a bigger tank unless you're ok with the
tankless for the single shower thing.
A 100 gallon tank is only 28" diameter by ~70" high maybe you might
room for it.
an alternative is to consider waste water heat recovery, if your house
is amenable to it, (geometry & plumbing wise) you might consider
their website is a mess but the concept & product are sound.
I've spent a fair amount on their website trying to figure the tihngs
In a ski situation most of the hot water use is for showers. These
things are perfect for heat recovery in a continuous flow situation and
properly sized that can "extend" gas fired water heater capacity by a
factor of about 3.
BUT the installation can be a problem ........... ideally you need 40
to 60 inches of drop from the shower drain to the sewer outlet for the
installation to be simple.......... otherwise you'll need a waste water
There's probably not a lot of room for a greywater heat exchanger either.
The one Gary Reysa and I are working on would be about 3' diameter x 6' tall,
with the greywater I/O near the top. If the 4" x 100' black corrugated
drainpipe spiral were flat (eg hung under a basement ceiling), it would be
about 7' in diameter.
That could increase the capacity with good final temperature regulation,
compared to putting the tankless after the tank :-)
yeah your best bet is probably putting a tankless, the highest btu your
propane tank will support immediately before the standard tank. you
will likely need to upgrade your propane setup..
with the tankless first this will temper the incoming water, warming it
enough that will allow your regular tank to finish it off for a stable
Step one - have a qualified propane service technician check the thing
out and make sure that the burner is adjusted and working properly.
Seems to me that there might (depending on location of shower) be plenty
of room for the copper system where the outgoing shower drain water
preheats the shower cold water supply (or even two of those stacked, one
feeding the shower cold and the other the water-heater inlet cold). This
is a commercial product (I forget the name), essentially consisting of a
copper drainpipe with a soft-copper water line wrapped around it and
soldered to it. By warming the cold into the shower it reduces
hot-water-use per shower.
Simple to install if there's a basement (or first floor) under the
shower, more complicated (wants a pump to elevate the drain water) if
the shower is on the lowest level of the building.
If space is lacking, suggest making a pancake shaped drain heat
exchanger and fitting it underneath the shower tray. The tray then goes
back 4" higher than originally.
Or a square tray with baffles fitted to control drain water flow
direction, and paralleled microbores running along those channels to
prewarm the cold feed to the shower.
The most primitive possible version, something one could set up in
minutes, could be nothing more than a copper coil placed in the
existing shower tray, with wood strips on it to keep feet off the cold
copper. Could be used as a temp measure while a permanent design was
Also ensure shower enclosure is fully closed to minimise conduction and
Hmmm. Something that sits inside the tub, eg 2 18"x36" copper plates
1/4" apart, bolted or brazed together with internal copper bar spacers
and a rubber mat or feet beneath, with a male hose thread at each end?
Or an all-copper bathtub, with tubing soldered beneath?
How would we keep it from cracking and leaking?
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
ISTR space was limited, so introducing a bathtub may not be the best
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
|| 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. :-)
DeSoto, Iowa USA
A small point. I don't think the "even" makes sense. The higher the
setting, for sure, the longer it will take to get there. If by "hot"
you mean the same temp regardless of the setting, it's going to take
the same length of time, because most heaters heat at full blast until
they reach the temp they are set for. Setting it to 140 instead 120
won't lengthen or shorten the time it takes to get to 120.
Set the temp higher so people will use less hot water and more cold
water? This won't shorte the time before the first shower is
possible, but if they don't shower then, the water will get hotter.
If it's really hot there may be a danger (especially children?)
What about limiting the flow of hot water (somehow) to make it last
longer and putting in an on demand heater to warm the cold water to
mix with the hot water. Or some strange combination of your current
WH and an on-demand heater, since neither alone is enough. I just
thought of this. For all I know it is a terrible idea.
That's similar. or the opposite, of what i just said.
When I was in the Navy, at one time, the shower for our berthing compartment
had rather *hot* water... You had to turn the cold water on first and then
just barely crack the hot water valve... If you did it the other way, you
had very wet steam coming out the shower nozzle... It was dripping one day
and I cranked down on the valve to stop it... Cranked down on the hot valve,
no difference... Cranked down on the cold valve, still no difference...
Cranked down *really* hard on the hot valve and it went from full off to
full on... I leaped out of the shower and half of me was lobster red... I
traced down the hot water line and once I came to the heat exchanger, I
found a temperature gauge... It was showing 250F hot water... The only
reason it was liquid was because it was under pressure...
The Navy is really big on impressing upon you to take "Navy Showers" instead
of "Hollywood Showers"... Since you have to make your water by distilling it
aboard ship and distilling means fuel, they want you to use as little water
as possible... To ensure this, they eventually changed all the shower heads
to a type of shower head that about the size of a hockey puck and was on a
hose... The shower head had a push button on it and you could only get water
as long as you were pressing against the spring loaded button... Spray
yourself, put the shower head down, soap up, spray the soap off... You
definitely used less water that way... After a long day of skiing, I suspect
that most people want a long shower... On the other hand, perhaps the OP
should just suggest group showers...
people tend to shower till they are warm. After a long day in the cold
this only makes things worse. a low flow shower head can help but the
tankless first feeding a regular tank would help a lot. if thats not
enough he could upgrade to a higher btu 100 gallon tank after the
tankless then set that tank HOT like at max then add a tempering valve
that would mix hot and cold water keeping output at 125 degrees to
the biggest gain would be the tankless and a good propane upgrade
A Takagi or Rinnai 190000+ btu unit will do the job itself without a
tank if the Gpm of the shower head matches flow capacity and temp rise
of your propane tankless. You need to know exact gpm output of showers,
incomming water temp lows, and measure temp drop from present tank to
shower head. Proper gas flow is the critical part 190000 btu is im sure
more than your present furnace, you need to have gas flow measured with
competing apliances on with a manometer. You might need all new propane
pipe and regulator to get the flow needed.
I use a small 117000 bosch with 35f incomming water I get a hot 105f
shower without unit set on high, without a real restrictive shower head.
You can get 1.2? gpm heads that a small 117000 Bosch will handle 2
showers, with 190000 btu you wont have an issue or need a tank , unless
altitude issues cannot be rejetted for.
I would hook up the tank but have a bypass valve set up since you may
not need it. Gas flow measured, incomming water temp low measured [ but
figure 35f] shower gpm output, and temp drop in pipe are what you need
I have my tank I replaced infront of the tankless , it is there only to
temper water to house temp. The most efficient, best unit made is a
Takagi TK1 a 94% propane fuel unit. I dought you will need the tank but
keep it inline with a bypass anyway.
Contact Takagi and Rinnai to go over the specs you need and for real
guidance, there might be a high altitude larger model avalaible that is
jetted and sized to get full Btu. It is all in temp rise, gpm, gas
supply+competing users, line temp drop, and knowing incomming temp low.
People unhappy with tankless are the ones that did not calculate
everything first, or installers cutting corners and guessing on gas
supply and pipe sizing.
The tankless solutions discussed elsewhere are probably
the best, assuming your propane system can keep up to the
Another possibility is to raise the tank setting, so you
have more heat energy available from it.
Alone, this isn't a good idea, because of the scalding hazard.
Some states mandate settings no higher than 120F... unless you
have a tempering valve.
If you set the temperature up high (eg: as high as 180-190F)
and used a whole-building tempering valve set to, say, 120F,
you'd have more heat capacity without the scalding risk, and
you're still "legal".
Switching to decent low-flow shower heads (if you haven't
already) will also help.
Chris Lewis, Una confibula non set est
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