water heater runs out of hot water?

[froggy_ss]

Hi there - I have a 74 gallon gas water heater from 1996. If you need the brand, I'll have to post from home tonight. Over the weekend, I tried to take a shower at the same time that my husband tried to take a bath - we both came up short - got cold water halfway through. I've noticed other times I've taken a bath at night that there doesn't seem to be enough hot water. But most of the time we dont' notice a problem. The water seems quite hot whenever we need it for short spurts. And during a normal shower I do not run out of water. The thermostat is set just a little above 120 - the dial does not have degress on it, it just has a big marking at 120 and we have it turned just above that.

Did we just use too much water when trying to both be in there at the same time? I can't see how we went through 74 gallons. I may have run a load of laundry on warm earlier in the day, like a couple of hours before ... I can't remember anymore (sorry) :wall:

[594tough]

74 gallons is a big WH for 2 people, or even for 4 people. You should not run out of hot in the circumstances you describe.

Although this sometimes begins to sound like a broken record, your symptoms are classic for the "dip tube problem". Also, the age of the heater makes this possible. If the dip tube is broken, then very soon after you start to use hot water, cold water coming in at the top is mixing directly with the water exiting the heater.

Check the website for your WH manufacturer. They will have an article identifying by serial number if your tank is affected.

Replacing the diptube is easy and inexpensive. You should do a thorough flush of the tank and the hot water piping to remove flaky particles.

[majakdragon]

A couple things to consider here. Although you have a 74 gallon tank, as soon as you start running hot water, the tank begins replacing that water with cold. With an energy efficient shower head (2-1/2 gallon per minute) a shower uses 25 gallons for a 10 minute shower. Even though part of that is cold water.
It could also be a defective diptube. The diptube sits under the cold water supply line pipe in the tank. The cold water is taken to the bottom of the tank through the diptube and thus pushes hot water out. If this tube is defective the cold water "short circuits" and goes right to the hot water discharge. They are easy and inexpensive to replace.
Have you ever drained and flushed the tank? Sediment will sit on the bottom of the tank and interfere with the burners ability to effectively heat the water. This is sometimes accompanied by a popping sound from the tank when the burner is on. I have included a link on proper procedures to do this. Just click on the link.
These are a few of the things that may be causing your problem. Good luck and reply back with any other questions you may have.

http://forum.doityourself.com/showthread.php?t=134483

[froggy_ss]

I've only lived in the house for 9 months - so no, I have not flushed it, nor do I know if it ever has been - I will show the link to my husband and see if we can give that a shot. I will also look into the dip tub - I may have questions after I read some more as I am a newbie at this :)

[Bob Haller]

Use care when draining, some drain valves are ALL plastic and may break upon opening, that happened to one friend of mine....

Its also a good idea to buy a cap that screws on the end of the valve in case it leaks after draining. Valves go bad all the time....

The cap will need GARDEN HOSE threads not pipe threads.

having a $2 can save a world of hurt.....