Water heater - how long should it run?

Anywhere from 15 minutes to 45 minute depending on the temperature of the water coming in. Municipal supplies here range from somewhat above freezing in winter (same for on-board tank in winter) to well over 75 F towards the end of summer after it has been 100+ every day for two months. After a couple days like that, water in the on board tank is warm enough to shower "cold."

Not only does cold temperature make a difference in how long to heat it, makes a big difference in how fast the hot water is used. When the cold water is icy, it gets mixed with a lot more hot water for a shower.

Camper Ken wrote:
With my previous motorhome when using the water heater on gas it would take an average of 20 minutes for it to heat up and shut down. Now with my current motorhome it's more like 45 minutes or more before it will shut down. Both water heaters are Atwood 6 gallon models. When I check the temperature of the water after 15-20 minutes (hand under the running water) it's very hot. Is this possibly a defective thermostat on my current model?

Mine is completely dependent on the outside air temperature and the water temperature in the tank before heating. I've had the range of time you've experienced. I also recommend checking water temperature making sure it is in spec.

If you want to (or are capable of this) run both the gas and electric heaters at the same time - this will get your water hot in a hurry!

Atwood uses a disc t-stat for normal and high temp
Normal t-stat is pre-set for 140*F and the ECO (Energy Cut OFF-----HI Temp) is pre-set for 180*F


IF the ECO Opens due to failure of normal (not opening) then the 'fault light' (RED light on On/Off panel will light up and water heater will not operate again until you reset fault...by turning ON/OFF switch OFF then back ON.
Water temp also has to cool down to roughly 110*F before reheating cycle will occur.

Normal t-stat CAN allow longer run time IF it is NOT being held tight against tank wall. The t-stats are under the foam insulating cover and are held in place by: Plastic washer, spring and three small tabs that plastic washer has to be under. (Really a poor design)
Also connections of t-stats need to be tight and clean


Have you run that hot water into a glass/mug with thermometer in it and checked temps?

Heating time should be roughly 20-30 minutes (depending on supply water temp and amount of hot water used)


On Edit:
Just FYI----Atwood does have an adjustable normal t-stat, Replaces pre-set disc t-stats.
Adjustable from 110*F to 150*F Part #93105 (it's mounting bracket is flimsy)