water heater problem

Hi, I was wondering if someone could steer me in the right direction on this.
I have a gas water heater in a home about 15 years. My water tank was replaced in 1996. The other day the service guy from the gas company said that there seems to be a problem related possibly to single lever faucets in that the cold pipe going into the water heater feels warm and the hot pipe feels cooler than it should be. He says that a plumber should come in and perform a diagnostic on this.
Basically, there is not enough hot water coming out with people taking consecutive showers. Can someone please elaborate as to what he was talking about. Also, I recently replaced a few valve stems for some faucets and shower controls provided free of charge by Moen. Is this related to the problem perhaps?
Thanks in advance for any insight.
Larry
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Larry L wrote:

He's right; single handle controls (especially old Moen) can cause mixing of Hot/Cold even when the faucet is Off. That dilution makes the Hot water colder. Washing machine fill valves can do it too.
If you just replaced all the single handle cartridges, then I guess you can rule that out.
There are other causes of not enough hot water: broken dip tube in water heater, gas control (thermostat) not responding.
Jim
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Another cause is the buildup of hard water scale in the tank, which effectively reduces the volume of water and decreases the time the water has to heat. That decreases the temp of the water getting to the fixtures.
If this is the problem, the cure is a new heater and a water softener to prevent the reoccurrence of scale in a new heater. Although you might try a softener first which will prevent new scale formation and dissolve some scale. Given enough time, which is usually about as long as the scale had to form, the softened water will remove all the scale. Usually though, the scale causes oil and gas fired heater tanks to fail long before their time.
Gary Quality Water Associates
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thanks Gary, but I'm sorry that I failed to mention that we have a water softener installed in the house from the beginning. Also, I have not replaced all the Moen faucet cartridges to my recollection and my washing machine is new. What about dishwashers? The water heater guy did take and replace a long plastic tube and brass/copper thing of some sort (i don't have it handy at the moment).
Cheers Larry
wrote

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I should have mentioned that if you have a softener, you need to make sure it is capable of handling the peak flow rates you have or hardness breakthrough will ocurr and that will lead to scale build up in a water heater. Or if it's allowed to run out of salt or the service run (time between regens) is too long hardness will get through.
The plastic tube is probably the dip tube, it takes cold water to the bottom of the tank.
Gary Quality Water Associates
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this is Turtle.
To start with go to your dictionary and look up what the correct spelling is for the following words. HOT , COLD , IN , OUT and get the correct definitions of each and then go to the top of the hot water tank and see what it says just beside the pipe that brings in the cold water to be heated up. this pipe should have IN or COLD wrote beside it. Then look at the pipe going into the top of the hot water tank which will supply the hot water to the house. this pipe should have the words OUT or HOT beside it. If this does not match the word and where they should be. your reverse feed the hot water tank and you will get a shortage of hot water. If the pipes are right, You have another problem which can be the inlet feed tube is off the inlet of the water pipe or the thermostat is malifuctioning.
If all the above is correct and no problem it could be the hot and cold water common to each other causing the problem , but i would not think this with the problem of not enough supply of hot water.
TURTLE
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Was there a problem before you installed the new faucets? I installed a single-handed Moen shower control that had scald protection (i.e., it would limit the amount of hot water) and had colder showers for a week until I had the time to fix it. Perhaps this is out of adjustment.
On 25 Nov 2003 13:55:12 -0800, snipped-for-privacy@home.com (Larry L) wrote:

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On 25 Nov 2003 13:55:12 -0800, snipped-for-privacy@home.com (Larry L) wrote:

The gas company guy should probably stick to gas problems...and not water problems. It doesn't sound to me like you have a problem.

How large is the heater? Have you always had this problem? Has your showering routine for the household changed?
Check the thermostat. Maybe somebody bumped it.
Wishing you and yours a happy Thanksgiving season...
Trent
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