Shower or Bath for Heat Efficiency

greenspun.com : LUSENET : Countryside : One Thread

Of course, it's always been given that the lesser amount of water consumed during a shower makes it far more efficient than tkaing a bath.

But I'm not so sure this is the case for those who have a thermostatically-controlled house. Here's why.

Let's assume a shower consumes ten gallons of water, and a bath 40. Your heat source - prbably a gas or oil-fired water heater, has consumed X amount of fuel to heat the water for the shower, and approximately 4X for the bath. HOWEVER....the shower water exits the house essentially immediately. For years now, I always have allowed the bath water to stay in the tub until all its heat has dissipated into the surrounding. Thus, all the calories burned to heat the water eventually also go to warming the house, too. Alternatively put, they diminish the amount of heat your furnace, etc., must furnish.

Now, this calculus doesn't account for non-thermostatically controlled setups, like woodstoves (except in a very gross way), and it can't help in situations - like hot summer days - when you want to do anything but add heat to your house (not a problem 11 1/2 months out of the year where I live). In the winter, however, I stand by my statement: a bath is more efficient than a shower.

We can discuss cleaning bathtub rings another time..... is why I

-- Audie (paxtours@alaska.net), December 04, 2001

Answers

I suspect you are right Audie although I am wondering just how much heat does go out with the shower water. Water leaves the rose in drops and droplets so the water has a lot of surface area for its volume and my guess is that by the time it reaches the floor of the shower cabinet it has given up most of it's heat anyway.

-- john hill (john@cnd.co.nz), December 04, 2001.

IF and only if the hot water heater is located in an unheated area of the house. (even then...) Think about it: the shower which uses (lets say) 10 gallons of water from the hot watr heater. Alot of the heat of the shower does dissapate as the water is falling- the droplets lose heat in a hurry. The water to suppy the shower, lets assume, came from a hot water heater. You had to run the well pump for however long it takes to pump 10 ghallons of water to the house (or pay for the 10 gallons of water if in the city). Now lets consider the bath. You use 40 gallons of water (lets say- or according to you figures 4X the amt of water) from the hot water heater. If that heater is located in a heated ara of the house- no matter how well insulated, it would have lost that heat that leaving the bath water in the tub would- thus helping to heat the house. If your hot water heater is located in a cold area of the house, then it would have lost that heat heating the air around the hot water heater, not the house. But with the bath method, you had to run the well pump (or pay for) 30 extra gallons of water. PLUS if you pay for sewage, you released 30 extra gallons of water. Or if you have aseptic tank, you released 30 extra gallons of water into the system that wasnt needed. PLUS the heating system on a house (gas or electric) is generally more efficient than the hot water heater- thus you spent extra energy heating the incoming extra 30 gallons of water that would have been better applied heating the house in a more efficient method. Course, ya can always sponge bath and save lots of cash, right (might lose a couple of friends, though=) The best (that Ive done so far) method is to cut the hot water heater back- mine was set at 135 degreesF, I cut it back to 96* and the electric bill instantly got cut in half. You have to open the hot water all the way up to take a warm shower, but the water heater runs a lot less (coils are hot= "runs").

-- Kevin in NC (Vantravlrs@aol.com), December 04, 2001.

Kevin:

First, you are right in taking into account the other externalities - the cost of pumping the water and paying for its removal. I neglected the latter, as I was assuming those in a Homesteading forum were not on city septic...and the former is truly trivial. Even at the 40 cents per kilowatthour I pay for juice it's less than one cent to pump the 30 extra gallons. More to bear is the waste of water - again, I missed on that - umm, it really really isn't a situation where I am, but it certainly must be for some others.

Your point of the location of the heater is not so clear. If by unheated you mean a basement, my calculus is valid - the d(heat) of that room will affect the upstairs; besides, much - though I agree certainly not all - of the heat generated was contained in the water, which as I submit then gets lost to the home air. And anything you might say about the water heater's location presumably would apply to the similarly-located furnace heater, so...

Yours and the prior post's point about water droplets losing much of their heat is well taken. That of course is a function of the d(air temp - water temp), as well as the trajectory each drop takes (hitting your skin, etc.). But I think you've a fair point there: my recollection is that shower drainage is significantly cooler on the toes if you poke 'em into the drain.

By the way, there's really no such thing as a hot water heater. Why would anyone want to heat hot water? <7;-)

-- Audie (paxtours@alaska.net), December 04, 2001.


I forgot: Kevin, you also said that it is more efficient to heat the house with the furnace, not the water heater. I agree absolutely, but that is separate from the issue I was bringing up -

A non-controversial way to approach this is to say - IF you take a bath, then for goodness' sake, leave the water in the tub until it's stone cold.

Now, about those bathtub rings....

-- Audie (paxtours@alaska.net), December 04, 2001.


An easy way to reduce the household hot water requirement is to parallel process those dirty bodies by putting two or more in the bath/shower at one time.

-- john hill (john@cnd.co.nz), December 04, 2001.


Audie; Haven't you ever heard the old song about "Grandma's Lye Soap"....please hum a few "bars" and think about the B T rings!!

-- Jim-mi (hartalteng@voyager.net), December 04, 2001.

I love this type of theoretical discussion!

Kevin, an electric water heater is 100% efficient, as is resistant electric heat. Gas is less than 100% efficient. A heat pump is more than 100%. You're right about the cost of power to pump the water; it varies, of course, depending on the depth, etc. of the well.

Audie, you pay 40 cents per kwh? Wow! You should seriously consider photoelectric, as you can actually save a bunch of money if you're paying that much, especially if you do an intertie system! (if you do a bit of shopping around, you should be able to get all your equipment for about ten bucks per watt; the equipment lasts for a looooong time, without batteries.

Audie, I agree with you about letting the water cool off in the tub. I hate tub baths, but with one of my wood powered water heaters, I had to fill the tub once or twice a day, to release extra heat, when the temperature approached boiling.

By the way, folks, a year or so again, I had a great idea for a new invention; this would capture most of the heat going down the drain from the shower. I planned to use a length of copper pipe to replace the existing plastic (or iron) drain pipe below the shower. Around this, I'd coil soft copper pipe, which would be preheated on its way to the water heater.

Then I found out someone had stolen my idea-ten or twelve years before I had thought of it.

Do a search for heat exchangers showers hot water energy, or something, on google, and you'll find out about it.

It can retrieve up to 80-90 percent of the heat from your shower water!

-- joj (jump@off.c), December 04, 2001.


AUDIE....I`VE BEEN THINKING OF BUILDING A COTTAGE.SEEING AS THERE WILL BE A WELL INVOLVED AND WATER IS LIMITED.SO RATHER THAN LET IT JUST GO DOWN THE DRAIN.I`VE CONSIDERED RIGGING UP A HOLDING TANK NEAR AND ABOVE THE WASHING MACHINE IN THE BASEMENT.THUS UTILIZING THE HOT WATER A SECOND TIME IN DOING THE LAUNDRY.THIS WOULD BE A SAVINGS IF YOU HAD OIL FIRED OR ELECTRIC HOT WATER.HEY,YOU MIGHT GET AWAY WITH LESS SOAP AS WELL...LOL! ANYONE EVER TRY THIS?WITH ALL THE SHOWERS AND BATHS TAKEN BY A FAMILY.THIS WOULD BE A CONSIDERABLE AMOUNT OF HOT WATER TO WASTE. SEEING AS I SHOWER DAILY THE WATER CAN`T BE THAT DIRTY.ASSOCIATED WITH EVERY SHOWER IS A PILE OF DIRTY CLOTHS AND TOWELS.HUMMM IT SEEMS LIKE THERE IS A USE FOR IT.

CORDWOODGUY

PS:I DON`T LIKE DOING COLD WATER WASHES.SO IF ANYONE SAYS TO USE COLD WATER AND NO NEED FOR HOT WATER FOR LAUNDRY.I`M A CONSTRUCTION SUPERVISOR AND ON OCCASSIONS HAVE SEEN OLD DRAINS DUG UP WHERE THE PEOLE USED COLD WATER WASHING.THE SOAP LAYED IN THE PIPES AND BUILT UP OVER TIME.EVENTUALLY CLOGGING THE PIPE OFF.THE PIPES LOOK LIKE THEY WERE FILLED WITH FAT OR CHALK.I LIKE HOT WATER WASHES BECAUSE THEY DON`T SEEM TO HAVE THIS PROBLEM AND IT RESULTS IN CLEANER WASHES.

-- CORDWOODGUY (cordwoodguy@n2teaching.com), December 05, 2001.


Hey, Cordwood guy. Are you sure that was really soap which was blocking up the plumbing? What kind of pipes were they using? I wonder if there was a problem with hard water, or something. The reason I'm asking is that I've used cold water for the washer for 26 years, now, and have never had a problem.

I also use a tiny fraction of the "recommended" amount of laundry detergent.

I've always known that the recommended amount was way more than necessary except in the most extreme hard water situations, and that soap manufacturers just want to sell more soap. My wife would never believe me, though. Then she bought one of those dumb Laundry BAlls.We did a test; she couldn't tell which loads of wash I did had been done with the laundry balls, and which had been done with no soap at all!

So now, she has to admit that a small amount of soap is plenty.

By the way, I'm totally in favor of running all grey water except kitchen sink out into the woods, onto a lawn, etc. Septic tank is the LAST place I'd want it.

-- joj (jump@off.c), December 05, 2001.


Funny that you should say that. (about the hot watr reclaimer) My father, back in 1973 "invented" this, also... He was working in a plumbing wholesale business at the time and thought of it one day, than found out, a couple of years later someone had patented it. Great Minds think alike=) What I meant about the hot water heater (yes- its a stupid name) being located in a heated portion of the house: If it is in a heated portion of the house, as it cools due to heat seeping through the insulation during its unused hours- that heat IS heating the house, you dont have to put it in a tub to retrieve it (although leaving it there if you do take a bath is wise). Ever think about this one: a Refrigerator/ freezer makes heat and needs to get rid of it. A water heater needs to make heat in order to heat the water. Why hasnt someone combined the two?! (the coils of the refrigerator dipped into the water tank or a pre heater tank of some sort) Another one I ought to patent;)~

-- Kevin in NC (Vantravlrs@aol.com), December 05, 2001.


However the math works out...I will not give up my clawfoot tub and those wonderfully relaxing hot baths :-)!!!!

-- Marcia (HrMr@webtv.net), December 05, 2001.

And, if you happen to be taking the shower in a tub/shower combo; you could put the stopper in the drain and let the shower water sit until it gave up all it's heat also. Any time of year that plants are still growing, I use the bath water for watering them. A cheap siphon from the discount store, a bucket or two, and a few minutes work; I don't need to feel guilty about using the water. I do make sure only to use it on ornamentals, trees and shrubs or plants that aren't bearing anything edible at the moment, in case of e-coli contamination.

I'm with you, Marcia; they'll have to pry me out of my claw-foot tub - that iron just holds the heat for hours, it seems!

-- Polly (tigger@moultrie.com), December 05, 2001.


Thank you, Polly! And when we drain the water...two of my cats run right in and sleep in the empty tub because it stays so warm :-)!

-- Marcia (HrMr@webtv.net), December 05, 2001.

Yeah, I love the idea of capturing heat from wastewater, too.

Some of you caught on to the problem of gumming up of drains from cold water washing. This, unfortunately, is one of the problems of any heat-capture system. Cool the water down, and your going to get exacerbated precipitation of sludge from the graywater.

Nevertheless, I agree with Cordwoodguy's thought of doing at least some combo. And at the very least, neglecting the calorie-capture part, any diverting of graywater to garden use is a good thing. It's even legal in some places! (For all of you poor saps who live in "civilized" places that have building codes and all that funny stuff ..... <7;-)

My clawfoot is long enough that I (6') can stretch out straight in it; and it is very deep. I made it really really deep by flipping the overflow drain 180* and extending its drain pipe up, before it goes down, so it's just about big enough for Flipper or Nanu!

That bathtub was the only thing salvaged from the original Paxson Roadhouse (built 1907), after it burned on Xmas Eve, 1975.

When I last traveled in New Zealand, I saw a number of long deep clawfoots. Astonished to hear they all came from Alaska! Some enterprising Kiwi traveller must have known a good thing when he/she saw them, and bot'em all up.

-- Audie (paxtours@alaska.net), December 06, 2001.


Our son in Japan has a computer operated bathtub. You set the temp and amount of water, bathe and the water is saved and reheated for another bath if you want. It will do this for up to three times for one bath. Of course you don't have to recycle the water if you don't want to. Our grandson bathes, his Dad uses his water and Mom has a fresh bath. Their stool also saves water in that it has a small basin with drain and faucet set into the top of the tank. When the stool is flushed, the tank fills via the faucet running into the basin and hands can be washed with this water.

-- Barb Fischer (bfischer42@hotmail.com), December 06, 2001.


To conserve on water, I was thinking of using a small pump to fill my toilet with used shower/bath water. I would plumb it through the wall cause'I don't have it drywalled yet. It might gross-out guests, so I might have to put one of those blue toilet cleaners in the water closet. Oh well...just another one of my wacky conservation ideas.

-- Keith (halfc@fidnet.com), December 06, 2001.

HEY,WE GOT SOMETHING GOING HERE.WE CAN GET SEVERAL USES OUT OF THE SAME HOT WATER

[1]BATH/SHOWER [2]LAUNDRY [3]RADIANT HEAT [4]WATER THE GARDEN OR THE LAWN.

JOJ...THE CITIES FINEST SAID IT WAS SOAP.MY FRIENDS THOUGHT IT WAS FAT.

KEVIN...SO MUCH FOR GREAT IDEAS.

AUDIE/POLLY/MARCIA....THANKS FOR THE INSIGHT ON THE CAST IRON BATH TUBS.I`M A BELIEVER NOW.I LIKE THE IDEA ABOUT THE HEAT RADIATING BACK INTO THE ROOM.

BARB....I`VE HEARD ABOUT THE SINK IN THE BACK OF THE TOILET.BUT I THOUGHT AS YOU WASHED YOUR HANDS IT FILLED THE TOILET RESERVOIR.THEN YOU FLUSHED IT WITH DIRTY WATER.

HEY,I NEVER HEARD ABOUT THE COMPUTERIZED BATH TUB. THERE WAS A SHOWER I ENCOUNTERED SOMEWHERE IN EUROPE.THE WATER RUNS ON A TIMER.

[1]YOU START THE WATER AND IT RUNS ABOUT 10-20 SECONDS.YOU ARE SUPPOSED TO GET WET. [2]THEN IT STOPS AND YOU LATHER UP.GOOD IDEA AS MOST PEOPLE STEP BACK AND LET THE WATER JUST RUN DOWN THE DRAIN. [3]YOU HIT THE BUTTON AND THE WATER COMES AGAIN.YOU RINSE. I THOUGHT IT WAS BROKE AND TOLD THE PEOPLE THAT THE WATER KEPT STOPPING.THEY THEN TOLD ME THAT IT CONSERVED WATER.GOOD IDEA.

WELL NOW THAT WE ARE TALKING ABOUT BATHROOMS. [1]PARIS HAS SOME CO-ED PUBLIC WASHROOMS.WITH NO DOORS ON THE STALLS. [2]I NEVER SAW REAL TOILET PAPER IN EUROPE.THERE WAS SOME THING LIKE FREEZER WRAP AND I WAS CONFUSED WHICH SIDE TO USE.I WENT WITH THE PAPER SIDE. [3]SOME WERE SO BARBARIC YOU HELD A POLE AND STOOD ON RAISED FOOT PRINTS AND DID YOUR THING.THEN AN ATTENDANT PUSHED IT DOWN A SHOOT WITH A SCRAPER.IT WAS AT A VERY LARGE AND FANCY RAILWAY STATION IN BARCELLONA I BELIEVE.[I WAS THERE FOR THE RUNNING OF THE BULLS.] [4]SOME PEOPLE TAKE A NEWSPAPER INTO THE TOILET WITH THEM AND CUT OUT A HOLE AND SIT ON THE PAPER.TO KEEP THEM OFF THE PUBLIC TOILET SEAT. AND I THOUGHT THEY TOOK THEN IN TO READ. [5]NOW WAIT UNTIL YOU HEAR THIS....I USED A BRICK OUT HOUSE IN ENGLAND WITH RUNNING WATER.WHEN I WAS DIRECTED TO GO OUTSIDE TO USE THE FACILITIES.I ALMOST LAUGHED IN THIS LARGE CITY ...THEY HAVE OUTHOUSES.IT WAS ON A COLLEGE CAMPUS.ANYWAYS WHEN I ENTERED I WAS SHOCKED TO SEE A WATER CLOSET WITH A CHAIN HANGING DOWN.IT FLUSHED. I THOUGHT IT WAS AMAZING.SO APPARENTLY IT CAN`T GET THAT COLD IN ENGLAND OR THE WATER WOULD FREEZE.IT HAD ELECTRIC LIGHTS AS WELL.

CORDWOODGUY

-- CORDWOODGUY (cordwoodguy@n2teaching.com), December 07, 2001.


I recently got a shower head that attaches to the shower and then has a ten foot hose and a nice shower head at the end. You can either use it as a regular shower or take it off the bracket and use it as a hand held shower. The thing I like about it is that once you have the water at the temperature you want it, it has a button to stop the flow of water and when you push it back on the water is still the same temperature because you didn't have to turn off the water by hand to stop it from coming out. This way, I only use a very little amount of water, i.e. get wet, turn off water, soap up, turn on water, turn off water, shampoo hair, then rinse off. I originally got it because I prefer to take baths but because my hair is so long the only way to really wash it was in the shower. Now, I can still have my bath but I can use the shower extension hose to wash my hair while I am in the tub. It also works well for giving dogs a bath in the tub because you can easily turn off the water when you don't need it and it is still the right temperature when you turn it back on.

-- Colleen (pyramidgreatdanes@erols.com), December 10, 2001.

I stumbled upon this posting while surfing, and got so caught up in the thread that I have not yet even looked to see what the main site address is! Here's my thoughts on showering and bathing for what they're worth: I shower and almost never bathe anymore. I moved 2 years ago and that is when I said goodbye to my clawfoot tub. It was the same tub I grew up with, as I had lived in, and come to own my parents house. I seldom miss it. I now have a tub with whirlpool jets I never use. (It was in the new house I purchased)I always plug the drain as I shower, to allow any heat left to dissipate into the air. I shut off the flow while soaping up, and turn it back on to rinse. I use a low flow shower head. (By the way, there are fittings with on off switches that thread on to the shower head to shut off the water.)I seldom use more than 5 gallons to shower.

-- Jack (jack@energy3.com), December 23, 2001.

Moderation questions? read the FAQ