Water Heater does not heat all 6 gallons

[bluefinger1]

I have a 6 gallon Suburban water heater, on the last trip we ran out of hot water much quicker than usual.

When we got home I ran the water heater, made sure it was nice and hot, then measured 3.5 gallons of water before it got cold.

If it wasn't heating at all, or just warm I could understand it, or if we were just blowing through all 6 gallons I could understand that.

But how could it heat only half of the 6 gallon capacity? Maybe an air bubble?

Thanks for your help.

[dougrainer]

If you have a DIP tube that has fallen OFF, Suburban will send you a new one. It is installed from the outside. Just leave the old one in the tank. It will not cause any problems. BUT, you REALLY need a digital actual temp of the full hot water output at the pop off valve. Have you done that? The factory tstat is 130 and you can buy and install a 140. Doug

[Old-Biscuit]

The PRV dripping would not affect heating ability.

It probably was dripping due to loss of 'air pocket' at top of tank.
Water expands and pressure increases when heated. The air pocket is there to allow the expansion...air can be compressed----water can't. So when air pocket is lost the pressure will increase enough to cause PRV to drip.
(See picture of WH tank in previous post)

Next time you find it dripping......re-establish the air pocket
Turn off water supply
Open closest faucet (Hot side) to relieve pressure
Open PRV via lever.......when water stops flowing let PRV snap close
Turn on water supply and close faucet.



I really think you have a dip tube that has fallen off.

[doxiemom11]

You will be surprised at the gunk that can accumulate in 1 year in the tank. We spent 5 months in an area with high lime content in the water. Even with our filters there was a lot of lime and calcium that drained out - looked like it had snowed or sleeted on the ground where it drained.

[bluefinger1]

ScottG wrote:
It heats all 6 gallons but you diluted it by adding cold water.

That makes sense, but we are getting significantly shorter showers this year than last year.

Thanks

[bluefinger1]

mbopp wrote:
Any chance the outside shower valves are open and allowing hot and cold water to mix?

There is no outside shower.

[ScottG]

It heats all 6 gallons but you diluted it by adding cold water.

[bluefinger1]

Old-Biscuit wrote:
What's you definition of 'HOT'?

I would define HOT as 120*+, it was this Hot tested by touch for about 3.5 gallons and got significanlty cooler, sub 100*.

I noticed the pressure relief valve was leaking and does not reset easily/completly. I know I will need to replace it, but do you think this would significantly affect the heating ability?

For what it is worth I drained the water heater by gravity and got 6 gallons, for safety reasons I drained it cold, at least I'm reasonbly confident it is filling up completely and I got minimal corrosion for
the first few seconds when draining.


Thanks again for everyone's help.

[bluefinger1]

Old-Biscuit wrote:
Hey OP

Just thought of something.....

Wonder if the dip tube on cold inlet has fallen off??

That would mix cold water quicker with the hot water resulting in lower overall temperature.
Drain the WH and with a good pin point flashlight see it if any black plastic part is laying in bottom of tank.

Some Black plastic did come our of the bath tub faucet this past weekend. It was pretty small, 2 pieces about the size of a quarter.

[Old-Biscuit]

Hey OP

Just thought of something.....

Wonder if the dip tube on cold inlet has fallen off??

That would mix cold water quicker with the hot water resulting in lower overall temperature.
Drain the WH and with a good pin point flashlight see it if any black plastic part is laying in bottom of tank.

[mbopp]

Any chance the outside shower valves are open and allowing hot and cold water to mix?

[queenie2]

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

[Old-Biscuit]

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

[naturist]

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.

[dougrainer]

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