Tank too small?


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Old 05-27-09, 08:29 AM
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Tank too small?

I have a 40 gal propane water heater and have a problem of running out of hot water. The unit has a 40,000 BTU burner and I have the thermostat set to the highest position. And still run out of hot water during a shower. Recently the town put in a new water system and the house pressure ranges from 80 to 90 psi.

Do all 40 gal heaters have the same 40,000 BTU burners? Would a pressure reducing valve increase the time that the heater provides hot water? Any recommendations for a replacement heater?
 
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Old 05-27-09, 03:55 PM
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How old is the heater?? Water pressure is a bit high, so a regulator valve is not a bad idea, but not likely the problem. Normal is 40-70#. My guess is the dip tube is gone. Pull off the cold inlet and check the tube. It should be a few inches shorter that the tank. if it breaks or rots away(white plastic bits in aerators), the hot water goes away quickly. There are replacements available, or you can make one out of copper.
 
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Old 05-28-09, 04:50 AM
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That's a good idea, thanks I'll check the dip tube. But, I normally don't have a problem with a typical "guy", 5-8 minute shower, it's my wife that takes 10 to 15 minute shower who has the problem. Could I check the dip tube by drawing a quart of water from the bottom drain and taking its temperature?
 
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Old 05-28-09, 12:36 PM
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Is your shower head a water-conserving 2 gpm flow rated one, or do you have one of those "rain forest" shower heads that puts out a huge amount of water?

Assuming 50/50 mix of hot/cold water, a 15 minute shower with a 5 gpm shower head will use a total of 75 gallons, or around 38 gallons of hot water, which is essentially your entire hot water tank capacity. Also remember that a 40 gallon water heater will not supply the full 40 gallons at the set temperature, as the hot water in it is constantly diluted with cold water as its being used.
 
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Old 05-28-09, 01:13 PM
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Retired Guy,

I would look at the shower head first. Beachboy's math is accurate, so if your wife insists on the 15 minute showers, change to a 2 GPM head if you don't already have that. And set the thermostat on the WH back to about 120 degrees before somebody gets scalded.

If the head isn't the problem, then look at the dip tube. Draining water out of the bottom of the tank won't tell you anything. You'll have to remove the cold supply line and nipple and actually pull the tube itself out.
 
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Old 05-28-09, 01:18 PM
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Thanks for the assistance. I'll look at the shower head and dip tube.
 
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Old 05-31-09, 05:19 PM
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A 40 gallon tank will deliver 28 gallons of water at "shower temp" ( more or less depending on exactly how hot you set the thermostat, and how hot you take a shower). That should give a 10 minute shower....how long do you stay in?
 
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Old 06-02-09, 06:02 PM
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The complaint of "not enough hot water" is one of the mosty common, and most vague. A lot of different things can cause such problems, or there may be no problem at all.


A good place to start is to measure how much hot water you get before the temperature declines to, say, 100 degrees.

Start by measuring the number of seconds needed to fill a five gallon bucket at a tub or shower outlet.

Let the water re heat, then measure the time it takes before the water temperature declines to 100 degrees.

A little division and you should be able to report how many gallons of hot water you are getting from your tank.
 
 

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