LP wtr heater, CO alarm

These units have a service life. Plus you have waited 3 times.

I would replace the LP Detector (probably not the CO unless it is a combo unit)

They have a 5-7 yr service life.expiration date stamped on backside of detector

Slim change propane for water heater is causing alarm to go off.....propane leak from water heater would be present 24/7 not just when in use

Replace the LP Detector

Are you at a higher altitude? I've experienced the same problem when leaving home (700 ft) and going to the mountains. Had to re-adjust the burner mixture control. Not enough oxygen getting to the flame.

Richard

If it's the CO detector that is going off when you run the water heater off LP, it could easily be the venturi tube for the burner that has gotten out of adjustment. Are you noticing excessive black smut near the water heater exhaust? If so, then the air/fuel mixture is off and that is usually due to the venturi adjustment sleeve moving over time making the mixture too rich. If you're not familiar with the adjustment, get a local LP supplier to look at it.

Don't know what type of water heater you have but on my Atwood, the LP lights off a burner and that blows heat through a hollow tube(maybe 3" diameter) that circulates around the water tank, and exits out the front to the exterior. I had some mud daubers build a nest inside the tube and this restricted the free flow of heat through the tube. This caused some of that flame to back feed and fumes could possible be leaking in to the interior of your coach.
Naturally it is also probable that your CO detector is original and since they have a service life of around 5 years, I am sure that yours needs replacing. All you have to do is take the CO detector loose and look at the back side and you will see the expiration date.

In reply to the suggestions:
Checking the date on CO detector found Sept 1999.
It was used at high altitude all three occasions, above 4000 feet.
Next step is to get new detector, check for burner flame color and
restriction in burner tube.

flagstickfrank wrote:
I have 2000 Itasca Horizon 36 DP. The last three times I've used the LP water heater the CO alarm has gone off. It works well with AC power but unable to use LP option that has worked very well for past several years. Any idea where to look? I can't find any path for the gas to get into the coach.

My water heater is directly behind my sink where there is a small window. Depending on the wind, the hwh exhaust will come in thru that window and set the alarm off. Also if my roof vent is open near the alarm and it is windy the hwh exhaust will come in thru there.

Some say if your hwh is burning properly it won't set the alarm off. All I know is depending where your hwh exhausts will depend if it sets the alarm off.

You should though check the lp lines leading to the heater doesn't have any leaks.