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Old 06-12-2009, 09:51 AM   #1
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Stumped. Water heater woes.


Hello, first post for me.

Run out of hot water while showering.

We had a A.O. Smith 50 gallon water heater. 12 years old. worked fine, but would run out of hot water towards the end of the second shower every morning. normal length shower and temp. Everyone told us it's probably calcium deposits on the lower or both elements.. or even an element is out. the elements checked out fine but it still happened.

SO, we replaced the water heater last week with another A.O. Smith 50 Gallon water heater. it does the exact same thing, but worse.

Should this water heater be able to keep up? I hear people with 3 kids in High School have no problems with a 50g. I filled the tub 1/2 way for my son... then my 6 year old daughter took a 10 minute shower and it started getting cold. and that was in the evening.


Thermostats are turned to 130* bottom and 135* on the top
I get a consistant 130* at the faucet running straight hot water
I am getting 240V at the heater
I get continuity across both elements

I swear to pete (whoever that is) that I can't buy anything that works properly these days. seems I have to do everything twice.

The shower head is normal and is the average Delta brand. so, it's not like it's dumping 80 gallons a minute or anything.


Please help.

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Old 06-12-2009, 10:20 AM   #2
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Stumped. Water heater woes.


In 1992 Congress fixed the maximum flow rate of a shower head at 2.2 gpm. Prior to that, showers put out as much as 10 gpm. If your shower head is more recent than 1992, you will get approximately 25 minutes of flow at maximum temperature of 130 degrees. You almost certainly do not shower at 130 degrees, unless you are planning a lobster boil, so you should get 35 to 40 minutes of flow from your shower before you run the tank out of hot water.

Since you do not define the term normal, I don't know how many minutes of shower you are describing. If the total shower time, plus normal use of other hot water, is less than 40 minutes, you should have adequate hot water for the entire period. If you are getting less than 40 minutes or so of hot water, you have a problem in the system.

There are other folks on this forum who are expert at hot water systems, perhaps they have some ideas on problems with heaters. Check old posts on how to verify proper function of elements. You might also check old forum posts on reverse installation of hot and cold water piping to a heater, I believe that was noted as a problem that could cause low volume of hot water.

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Old 06-12-2009, 10:27 AM   #3
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Stumped. Water heater woes.


Daniel,

Thank you for your time.

the water heater was installed exactly the same as the older one. the inlet has a blue cap and the outlet has a red cap. I followed the blue one back to the incoming pipe from the well and the red cap went to the tub. exposed ceiling in the basement helps

--I'm going to measure my GPM from the shower head.
--I'll triple check incoming cold pipe
--I'll run a timer for the length of shower I'm thinking maybe 25 minutes. maybe not even that much.
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Old 06-12-2009, 10:42 AM   #4
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Stumped. Water heater woes.


BC, The GPM should be printed on the shower head. FYI, I was in a hurry today so I showered in the ensuite while my son was in the other shower. I use a recent model low flow delta head , his is a low flo NIAGARA I believe. He takes LONG 30 minute showers , then my wife does, then me so 3 showers all within 1 hour, we never run low...
We have an 8 yera old 50 Gallon GE, 35 year old home with 1/2" piping. I also ran a load of wash and the dishwasher this a.m. before he started showerring...
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Old 06-12-2009, 10:49 AM   #5
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yeah. there must be something wrong. I'm thinking the lower element is bad.

I'm gonna borrow an OHM meter tonight and check the resistance on the elements. frustrating.

I mean, my wife gets a shower at 6:30 and I get one at 6:45.... and I'm out within 8 minutes or so..

Might just have to start taking showers with the wife



I'll report back with GPM listing.
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Old 06-12-2009, 11:48 AM   #6
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Stumped. Water heater woes.


With two different properly installed HWHs giving you the exact same problem, I'm wondering if maybe your ground water temp is very low? Or your family likes very hot showers (I know I do..)

When did this start happening with the old unit? Can you pin down anything else that might have changed around the same time?

Quote:
Originally Posted by bigcaddy View Post
Might just have to start taking showers with the wife
Umm.. are you sure that's the right emoticon for that?

Though at 6:45AM my emoticon is / regardless of what I'm doing..
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Old 06-12-2009, 11:56 AM   #7
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running out of hot water never really bothered me because the hot water used to last a lot longer.. usually never had a problem unless the wife decided to shave the legs......not mine either.

but the new water heater is worse..
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Old 06-12-2009, 12:52 PM   #8
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It's possible that the dip tube from the first heater disintegrated and has lodged pieces in your plumbing system. There was a class action law suit on this 10 (or so) years ago. You might be able to take apart some of the hot valves for your sinks or shaower and see if there are any signs of "chunks".
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Old 06-12-2009, 01:18 PM   #9
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OK, despite my advanced age and lack of wisdom, let's think this through. You are not taking excessively long showers, and yet you are running out of hot water. Since the water starts hot, the problem is not in the shower mixing valve. Similarly, you have hot water to start, so the water heater is working to some extent (not a total failure).

Low temperature groundwater does not explain the problem, since the water reaches 130 degrees (you already measured that), therefore regardless of the starting water temperature, you are reaching operating temperature.

Even if one element in your heater were burned out, you still should have a full tank of hot water to start, it should simply take longer to get to temperature, but overnight should be plenty of time to reach full temperature. And 50 gallons of hot water should be plenty of water for two showers, a load of laundry etc.

Therefore, Dr. Watson, you must not have a full tank of hot water in the morning. Based on your experience, you probably half a tank or less of hot water. This is hard to explain, since the water should mix, but in the immortal words of Sherlock Holmes, when you have eliminated the impossible, then whatever remains, no matter how unlikely, must be the truth.

So to verify this hypothesis, I suggest the following. In the morning, shut the cold water intake to the water heater, turn off the breaker to the heater, and proceed to drain the tank via the drain valve at the bottom of the tank. Measure the temperature of the water as it leaves the tank using your thermometer. Measure the amount of hot water in the tank using a 5 gallon bucket. My theory is that you will find that there is 25 gallons or so of hot water (130 degrees), and the remainder of the water is cold.

Once you have made the determination, we can move on to probable cause and repair.
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Old 06-12-2009, 01:54 PM   #10
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ok, I will try that. I guess my question would be wouldn't draining it from the bottom only produce cold water for the 1st 1/2?
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Old 06-12-2009, 02:09 PM   #11
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Your water heater should have two elements, one near the top (or possibly the middle), and one at the bottom. It probably also has two thermostats, one for the lower element, one for the upper. When either thermostat senses cold water, it turns on the heating element, which stays on until the water warms to the set point (130 degrees in your case), then shuts off until the water temperature drops again.

Hot water is withdrawn from the tank from the top, and cold water enters the tank via a dip tube (a plastic pipe) that sends cold water to the bottom. Since cold water is naturally separated from hot water because it is denser, as you take a shower, you withdraw hot water from the top of the tank, and the tank gradually fills with cold water from the bottom. There is limited mixing of hot and cold water, however there is some mixing, which is why manufacturers recommend that you size your tank for 20 percent greater capacity than demand, i.e. if you expect to used 40 gallons of hot water at one time, you get a 50 gallon tank.

As soon as the cold water enters the bottom of the tank, the lower element should turn on, and begin to warm the water. The upper element turns on when you have used up enough hot water that the upper thermostat senses cold water and turns on.

Over the "recovery" period of the unit, all of the water should be heated to 130 degrees, so by the morning, the whole tank should be filled with hot water. The first inch or so of water at the bottom of the tank might be a little bit colder than the rest of the tank due to incomplete mixing, but it certainly should not be cold. If it is, you probably have either a failed lower thermostat or a failed lower element.

If your dip tube is broken, cold water would enter the tank higher than expected, possibly even at the top, and you would have the potential that even though the tank had plenty of hot water, you would be "short circuiting" the system, and you would experience a lack of hot water condition.
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Old 06-12-2009, 02:25 PM   #12
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Stumped. Water heater woes.


Quote:
Originally Posted by bigcaddy View Post
I'm gonna borrow an OHM meter tonight and check the resistance on the elements.
Should be 13 ohms, give or take

When the dip tube disintegrates you'll find white, shell-like particles in the sink.

Raising 50 gal. of water (450#) from 70F to 130F takes 8 kwh, and at 240v and 9kw it takes 53 min. Does it heat that long?

Last edited by Yoyizit; 06-12-2009 at 02:36 PM.
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Old 06-12-2009, 02:33 PM   #13
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Stumped. Water heater woes.


sounds to me like the water heater was not full of water before you turned on the breaker to it which would blow the element.
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Old 06-12-2009, 02:52 PM   #14
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I am certain it was completely full before the power was turned on. I vented the tank until the water came out of the vent then ran the water from both hot and cold upstairs to purge the system of air. then I tuned it on and you could hear it make that hissing sound when it heats


Thank you for posting the OHM reading.
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Old 06-12-2009, 02:57 PM   #15
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Stumped. Water heater woes.


I am not sure how long it takes to heat up. I hope the dip tube hasn't started to disentegrate. only been in use for 4 days.

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