How much hot water is available with a 40 gallon water heater?
Avinash Chopde
So I've moved into a new place recently, renting an apt inside a house,
and I discovered that it barely supplies hot water for around 15-20
minutes - bathroom or kitchen use only, only one tap running at any one
time, and there is no washer/dryer here.
My apt has its own water heater, a 40 gallon gas unit, with 28,000 BTU.
The thermostat is turned way up to "hot" on the heater.
It seems strange to me that this heater does not provide more than
15 mins of hot water - it may be that I use more hot water than
normal" (!) people, but I've never had this kind of problem in any
previous houses I've lived in, usually get hot water for as long
as I want it.
The gas repairman thinks that 28,000 BTU is too low for a 40 gallon
heater, and that is the problem. Someone else told me that maybe the
thermostat is the problem, and is not kicking in soon enough.
I'm now wondering what should I expect from this heater - is it normal to
run out of hot water in 15 mins - just running the shower, with
warm-to-hot temperature water? No other tap or water outlet is being
used.
Thanks for any info!
--
----
Avinash Chopde
e-mail: avi...@acm.org
home: http://www.paranoia.com/~avinash/
Gary Slusser
Avinash Chopde <avi...@paranoia.com> wrote
If you have hard water there could be enough scale buildup to cause the
problem. The scale will be on the bottom of the heater and it doesn't conduct
heat very well. It will increase the time needed to raise the temperature and
thereby you get cool water.
Gary
Jim Sokoloff
avi...@paranoia.com (Avinash Chopde) writes:
> My apt has its own water heater, a 40 gallon gas unit, with 28,000 BTU.
> The thermostat is turned way up to "hot" on the heater.
>
> It seems strange to me that this heater does not provide more than
> 15 mins of hot water - it may be that I use more hot water than
> normal" (!) people, but I've never had this kind of problem in any
> previous houses I've lived in, usually get hot water for as long
> as I want it.
The fill tube is possibly broken, allowing the cold water to come in
near the top of the tank, causing it to "run out" sooner. Not sure how
to verify this other than visually or by eliminating other possible
causes, causing you to visually check it. Checking it is not
trivial. :-)
Or:
Have you flushed it recently? It's possible that there's so much rust
and sediment at the bottom that the heater can't effectively heat
water. (I recently did this for some friends of mine who were renting
and the landlord had already installed low-flow showerheads and
"everything he could think of" to fix it. They got literally less than
60 seconds of warm water before it ran cold; their gas burner was
tripping a high-limit safety before it really heated any water... We
took out about 20 bucketfuls of water, at first each was horrible
looking, eventually the water was almost clear. Being able to flush by
hose wasn't an option as there was no open drain.)
So, flush the tank well. I'd imagine most landlords don't do it ever,
and you should probably do it once a month or every other (being
perhaps a bit more realistic.)
To flush (from memory, rather than a book, so read more if you don't
feel comfortable with these directions):
1. Turn the heater to pilot or off (on an electric, turn it off).
2. Turn off the cold water supply to the tank (hopefully this will be
near the tank and separate from the whole house supply. Run the hot
water for a minute and feel the pipes to learn which is hot and cold
in your setup.
3. Find a place to dispose of the water (a sink or sump pit is ideal,
so you can use a hose) Otherwise, get a bucket to haul it to a sink or
toilet.
4. Connect hose to drain valve outlet
5. Open drain valve
6. Open a hot water tap in the house.
7. Let the tank drain and then I like to cycle the cold water valve to
give some mechanical agitation to the bottom of the tank. (On for 10
seconds, off for 30, repeat a few times, and then on for 1 minute, off
until drained, repeat until you're satisfied or tired, etc.
8. Close the drain valve, remove the hose
9. Turn the cold supply valve on and while the tank is filling, go
close the house tap once water starts coming out.
10. Turn the heater back on (undo step 1, visually determining that
the pilot is on)
11. Go through the house and run several gallons of water from each
hot tap. (In my house, the first time I did this, I stirred up a ton
of rust and sediment, so I wanted to get this out of the taps when I
was thinking about it, rather than into a load of white laundry... So,
run the washer empty for a load on hot.)
12. You might have to repeat step 11 after a few hours when the tank
has gotten hot and the sediment has all gone to wherever it wanted to
temporarily rest.
13. Consider cleaning the screens in the faucets, particularly if you
got a lot of crap out of the systems in 11 and 12.
Whole process takes maybe 1-2 hours first time, less after that,
assuming the drain valve doesn't break (which I gather from others
that they do; has never happened to me).
---Jim
Topher Eliot
>To flush (from memory, rather than a book, so read more if you don't
>feel comfortable with these directions):
>
>1. Turn the heater to pilot or off (on an electric, turn it off).
Believe it or not, on some gas water heaters, turning the knob to
"pilot" does NOT disable the main burner. This was the case with the
one at my last house. Instead, one must turn the thermostat knob
to "Vacation". Make sure you disable the main burner, because if
it runs while the tank is empty, you can damage the water heater.
Ditto with electric heaters.
Topher Eliot
el...@alum.mit.edu
Visit the house maintenance archive at http://www.geocities.com/heartland/7400
Mark A.
In article <01bd4914$e7bae240$879d...@qwasluss.ptdprolog.net>
"Gary Slusser" <qwas...@ptd.net> writes:
>
>
> Avinash Chopde <avi...@paranoia.com> wrote
> > So I've moved into a new place recently, renting an apt inside a house,
> > and I discovered that it barely supplies hot water for around 15-20
> > minutes - bathroom or kitchen use only, only one tap running at any one
> > time, and there is no washer/dryer here.
> >
> > My apt has its own water heater, a 40 gallon gas unit, with 28,000 BTU.
> > The thermostat is turned way up to "hot" on the heater.
> >
> > It seems strange to me that this heater does not provide more than
> > 15 mins of hot water - it may be that I use more hot water than
> > normal" (!) people, but I've never had this kind of problem in any
> > previous houses I've lived in, usually get hot water for as long
> > as I want it.
> >
> > The gas repairman thinks that 28,000 BTU is too low for a 40 gallon
> > heater, and that is the problem. Someone else told me that maybe the
> > thermostat is the problem, and is not kicking in soon enough.
> >
> > I'm now wondering what should I expect from this heater - is it normal to
> > run out of hot water in 15 mins - just running the shower, with
> > warm-to-hot temperature water? No other tap or water outlet is being
> > used.
>
> If you have hard water there could be enough scale buildup to cause the
> problem. The scale will be on the bottom of the heater and it doesn't conduct
> heat very well. It will increase the time needed to raise the temperature and
> thereby you get cool water.
This doesn't explain Avinash's symptoms. This would effect recovery
only and it appears that he is running out of hot water well before the
tank empties. I'd say the problem is one of the following:
1) Malfunctioning thermostat - measure the output temperature of the
water once it stabilizes. If it is 120F or higher, then the thermostat
isn't the problme.
2) Stratification (hot water is layering towards the top of the heater
due to infrequent use) - Try running hot water for ~5 minutes 30
minutes prior to taking your shower.
If neither of these turns out to be the root cause, you're a water hog!
;-)
Mark A.
Phil Munro
run until the gas turns off. Then *turn the gas* to pilot only. Got ot
a sink where you can fill a bucket, measure the amount of water
(gallons) that the bucket holds, turn on the water and *measure* the
number of gallons you get before it goes cold.
Another way to do this would be to measure the rate of hot water,
gallons/min, and see how many gallons that works out to be in 15
minutes.
You may just have a higher rate of delivery from what you are used to
in other places. Forty gallons in 15 minutes is just under 3 gals/min.
--
Phil Munro Dept of Electrical Engineering
mailto:pcm...@cc.ysu.edu Youngstown State University
Youngstown, Ohio 44555
Gary Slusser
Mark A. <Lo...@the.sig> wrote
The tank never empties. Aren't you forgetting that for each gallon of hot
water used a gallon of cold enters and thereby there are not 39, or any other
number of gallons of hot water for constant use? He'd have to shut the cold
water feed off and drain the tank to get 40 gallons of hot water. The recovery
rate of a heater dictates the available time of use, no? Anything that
interferes with recovery will decrease temperature while the heater is heating
and water is being used. And if the water is hard a gas or oil fired heater
will lose more recovery than an electric because scale build up is on the
bottom where they apply heat, rather than an electric element that sloughs off
the scale to fall to the bottom of the tank.
Gary
> 1) Malfunctioning thermostat - measure the output temperature of the
> water once it stabilizes. If it is 120F or higher, then the thermostat
> isn't the problme.
>
> 2) Stratification (hot water is layering towards the top of the heater
> due to infrequent use) - Try running hot water for ~5 minutes 30
> minutes prior to taking your shower.
>
> If neither of these turns out to be the root cause, you're a water hog!
> ;-)
>
>
>
> Mark A.
>
>
>
Doug Miller
In article <35043D...@cc.ysu.edu>, Phil Munro <pcm...@cc.ysu.edu> wrote:
+Mark A. wrote:
+>
+> In article <01bd4914$e7bae240$879d...@qwasluss.ptdprolog.net>
+> "Gary Slusser" <qwas...@ptd.net> writes:
+>
+> >
+> >
+> > Avinash Chopde <avi...@paranoia.com> wrote
+> > > So I've moved into a new place recently, renting an apt inside a house,
+> > > and I discovered that it barely supplies hot water for around 15-20
+> > > minutes - bathroom or kitchen use only, only one tap running at any one
+> > > time, and there is no washer/dryer here.
+> > >
+> > > My apt has its own water heater, a 40 gallon gas unit, with 28,000 BTU.
+> > > The thermostat is turned way up to "hot" on the heater.
+> > >
+> > > It seems strange to me that this heater does not provide more than
+> > > 15 mins of hot water - it may be that I use more hot water than
+> > > normal" (!) people, but I've never had this kind of problem in any
+> > > previous houses I've lived in, usually get hot water for as long
+> > > as I want it.
+> > >
+> > > The gas repairman thinks that 28,000 BTU is too low for a 40 gallon
+> > > heater, and that is the problem. Someone else told me that maybe the
+> > > thermostat is the problem, and is not kicking in soon enough.
+> > >
+> > > I'm now wondering what should I expect from this heater - is it normal
to
+> > > run out of hot water in 15 mins - just running the shower, with
+> > > warm-to-hot temperature water? No other tap or water outlet is being
+> > > used.
+> >
+> > If you have hard water there could be enough scale buildup to cause the
+> > problem. The scale will be on the bottom of the heater and it doesn't
conduct
+> > heat very well. It will increase the time needed to raise the temperature
and
+> > thereby you get cool water.
+>
+> This doesn't explain Avinash's symptoms. This would effect recovery
+> only and it appears that he is running out of hot water well before the
+> tank empties. I'd say the problem is one of the following:
+>
+> 1) Malfunctioning thermostat - measure the output temperature of the
+> water once it stabilizes. If it is 120F or higher, then the thermostat
+> isn't the problme.
+>
+> 2) Stratification (hot water is layering towards the top of the heater
+> due to infrequent use) - Try running hot water for ~5 minutes 30
+> minutes prior to taking your shower.
+>
+> If neither of these turns out to be the root cause, you're a water hog!
+> ;-)
+ Here is another idea. Let the water heater stabilize, that is, let it
+run until the gas turns off. Then *turn the gas* to pilot only. Got ot
+a sink where you can fill a bucket, measure the amount of water
+(gallons) that the bucket holds, turn on the water and *measure* the
+number of gallons you get before it goes cold.
+ Another way to do this would be to measure the rate of hot water,
+gallons/min, and see how many gallons that works out to be in 15
+minutes.
+ You may just have a higher rate of delivery from what you are used to
+in other places. Forty gallons in 15 minutes is just under 3 gals/min.
It might also be worthwhile to check the connections to the water heater.
When we bought our house, the water heater would produce about a minute
of scalding-hot water followed by more than half an hour of tepid water.
Called the previous owner, and learned that it had "always been that way."
Turned out that an earlier owner had mis-connected the pipes: cold water
to the outlet, and hot water to the inlet, so that hot water was being
extracted from the bottom -- and 50-degree well water was being dumped
in at the top, where it would sink, rapidly cooling the entire tank as
it did so. Reconnecting the pipes properly solved the problem.
Tommy Dougherty
> It seems strange to me that this heater does not provide more than
I don't know if this has been suggested yet....
But have you checked elements to see if one burned out?
(You can do it w/ a continuity meter)
In my last house (townhouse), one of the elements died, and we had maybe
15mins of hot water until I put a new element in.
-Tommy