Natural gas hot water heat.

We find that when the hot water has not been used for several hours there will be not sufficient hot water for a bath. If we for example, run the dishwaher before the bath, there will be enough hot water. Does this sound like the tank needs replacing? Tx, your suggestions please. jesse

gas? electric? cold temp in? hot temp out? dip tube needed? electric element failure? take some water temperatures and check out your electric or gas water heater troubleshooting. i'd temp check then bump up the thermostat setting hotter and temp check in a few hours. use a digital thermometer from the kitchen. see: http://www.waterheaterrescue.com/pages/WHRpages/English/Troubleshooting/not-enough-hot-water.html

yep, how old is the heater?
Jesse wrote:
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It is a 40 gallon natural gas manufactured in 1999. I drained the tank completely tonight after our baths and will see how it behaves following this. I did not notice any debris in the water drained. Tx four your reply. jesse

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Could be the thermostat low limit. As the water sits, it cools down and the thermostat should kick the burner on to bring it back up. See if there is a setting for it.

yeah turn thermostat up just a little.
hope they turned OFF the burner or electric before draining tank!

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I did not realize these thermostats had low limit settings. Is the setting hidden under some cover or screw?
I have a similar problem, but not quite as bad. If the hot water has not been used for a while, it comes out at least 10 deg cooler, than with use.
Rich

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What a coincidence: I installed a brand new State 50-gal NG heater about three weeks ago and have noticed the SAME thing. It is NOT annoying enough that I am anxious for a "fix", but I HAVE noticed the cooler (less hot?) water after a period non-use.

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Mine is also made by State a 40gal, but a few years old. Beginning to wonder.
I've been at this place for not quite a year and noticed it right away. Have not observed this on any other heater before.
RichK

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Ours is a 40 gallon made for Sears in 1999, I've drained the tank then refilled and turned up the temp a bit. We will know tonight as we are both away in the afternoon and we will try the bath before running the dishwasher. Fenny wants me to replace the appliance but I'm not convinced that it will solve the situation. There must be a solution, I was convinced that the bottom of the tank was silted but on draining everything that came out was clean. We need more suggestions please Tx. jesse

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Been thinking, although this may not be your situation.
In the past, I used to set the heater much hotter, so I could not hold my hand under the hot water and easily compare.
With the present heater, I've been running it much lower, such that I can hold my hand in the running hot water. Now I can tell the diff and confirm with a thermometer, when it's hotter or not as hot.
Before it never occurred to me to measure the temp - it was always HOT. Perhaps the differential was always there.
RichK

Thermstats arent precision instruments. The 10 degree bounce you see is probably normal for your tank.
theres a easy work around as soon as you get home run some hot water. this will trip the burner on, and reheat the water.
although its easier to just set the temp up a little.
you will also notice that after using lots of hot water the temp can end up more than normal

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The setting is not user accessable. It is determined by the control unit and generally tracks with the setpoint.
This is normal and depending on the tank size, efficiency of the insulation and frequency of your use, you'll notice it more or less than others.
To deal with it, I run the hot into the tub until it feels warm then stop and wait 15 min for the WH to heat to full temp. That little bit of water I use to prime the Hot pipe causes enough cold to be introduced into the tank to kick on the burner but not so much it that takes a long time to heat up. When I return the hot tap is primed and the tank is topped off at max set temp.
Similar to you using the dishwasher but more optimized to filling the tub. I probably don't even need to run the hot as much as I do to het the WH to light.
Without this trick, I could not fill my tub at one time, 30-45 min to heat a depleated tank to usable temp.
PS my hot pipes are insulated.

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I've discovered that there really is a solution to the water hot too late problem. One could install a timer controlled re circulating pump to move the hot water resulting in hot water on demand. The pump alone here is priced at $450 so it will be the dishwasher first for us. Thanks for all your thoughts. jesse

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The tank was made in 1999, which I think was right during the time frame for a lawsuit regarding the plastic used in dip tubes of that era - they crumble & disappear in the tank because they changed the formula for the plastic. Check for a missing dip tube on the cold water intake. It's a $10 part.
Also, make a heat trap out of copper pipe on the hot water side. I did that to mine and the heater doesn't light up as much as it used to - the heat stays in the tank, it doesn't radiate through the pipes anymore (makes insulated pipes unnecessary). I don't think the 6" long heat traps you can buy will do much good nor last very long because they are nothing more than nipples with rubber flapper valves in them. Making one out of copper pipe or a long section of copper flex tube will last forever and always work - laws of physics.
Otherwise it sounds like a normal hot water heater that just doesn't get used enough. Mine acts this way sometimes, and sometimes I've set my dishwasher to delay starting for about 4 hours after I go to bed so that I'll have HOT water in the morning.

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Could you please tell me more about this heat trap made from copper pipe. Tx jesse

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It's nothing more than a loop of pipe, or flex tube. It needs to be 6-12" tall. Here's what happens: Heat rises, but it won't sink, so the heat goes up one side of the loop and across the top but not down the other side. Two long straight pieces (9-12"), two short straight pieces and 4 elbows are all you need to make this happen. I've heard it can be made by taking a 36" flex tube and bending it into a loop, but (IMO) flex tube isn't much more flexible than copper pipe.