Water Heater does not heat all 6 gallons

Good comment, Old Biscuit. I was wondering that my self.

What's you definition of 'HOT'?

Incoming source water temperature & flow rate will affect the output temperature.

Suburban normal t-stat is preset for 130*F (OPENS) and will not CLOSE until roughly 100*F for reheating.

Recovery rate is ~10 GPH on propane and ~6 GPH on electric with 70*F inlet water temp.

Yes it's a 6 gallon tank......but flowing straight hot water out of it will not give you 6 gallons of hot water (HOT being defined as 120*F)

Not sure how you will accomplish measured test by draining via gravity....pulling the drain plug/anode rod with tank full of hot water will be interesting.

ON EDIT:
Those wondering about RV WH design.
Small curved 'dip' tubes are on cold inlet (pointed down) and hot outlet (pointed up).


One of the difference between Atwood & Suburban is the combustion/exhaust heat tube design.
Suburban combustion chamber is on bottom right side and exhaust is directly above it on right side. Heat tube is basically a straight 'U' Tube.
Atwood combustion chamber is on bottom right side and exhaust is on top left side. Heat tube goes more through 'middle' of water tank. More contact surface/more heat transfer.

Suburban


Atwood

I'm not sure about the design of RV water heaters, but I know about residential ones, which are designed to draw in the cold water at the bottom of the tank in a way to minimize the mixing. This is why those tanks switch from hot to cold so quickly when they run out of hot water.

Since the cold in line comes in from the top of the tank there is an internal cold pipe clear to the bottom of the tank. As I recall looking at the tank in my TT, the cold line enters the tank at the bottom. If there is just enough crud built up to deflect the cold upward in the tank, it'd mix with the hot pretty early in the process, so it might not take all that much crud to cause this, if shaped and located just right.

1. Did you leave the LP burner system ON after it heated up or did you turn it off to do your gallon test?
2. Are you POSITIVE that your bypass valves(if you have them) are set correctly?
3. WHAT is the actual water temp AT the pop off valve> You have to release it to get this temp. It SHOULD be 140 or higher. That is the ONLY place to get an accurate reading of the water temp. If lower than 140, that is your problem. If over 140 and at the Hot water spigot closest to the water heater it is NOT 140 or higher, then you are mixing cold with hot after it leaves the water heater. Doug

Francesca Knowles wrote:

bob_nestor wrote:
Not trying to be a smart a$$ here, but the hot water is discharged by pumping in cold water. That cold water mixes with the hot water remaining in the tank reducing the temperature. At about 3 or 4 gallons the hot water will be fairly cool. The amount of hot water one gets out is dependent on the temperature of the cold water coming in too.

First thing that crossed my mind, too.

But surely the O.P. thought of that and turned the incoming water off and then finished the "test" via draining by gravity into a measuring vessel...

Right, O.P.?

Wrong, I did it the dumb a$$ way. I did expect it to cool off, just not as quickly as it did. I will try it again by turning off the water and gravity feeding it.

Thanks all for your suggestions.

And certainly, if you are filling a tub or bucket with hot water at full speed, the mixing effect will take place much faster than sipping at the hot water with the burner on during a navy shower.

bob_nestor wrote:
Not trying to be a smart a$$ here, but the hot water is discharged by pumping in cold water. That cold water mixes with the hot water remaining in the tank reducing the temperature. At about 3 or 4 gallons the hot water will be fairly cool. The amount of hot water one gets out is dependent on the temperature of the cold water coming in too.

First thing that crossed my mind, too.

But surely the O.P. thought of that and turned the incoming water off and then finished the "test" via draining by gravity into a measuring vessel...

Right, O.P.?

Not trying to be a smart a$$ here, but the hot water is discharged by pumping in cold water. That cold water mixes with the hot water remaining in the tank reducing the temperature. At about 3 or 4 gallons the hot water will be fairly cool. The amount of hot water one gets out is dependent on the temperature of the cold water coming in too.

is the units a true 6 gallon unit? or a 6 gallon usable.

based on the fact people don't shower at full hot, thus mixing cold, which makes it 6 gallon usable?

Huntindog wrote:
Probably full of calcium and junk reducing it's capacity.
You can try removing the plug or anode rod and flushing it out.

It is only a year old, but I'll check it.
Thanks