Hot Water Mystery

[Racharoo76]

We just picked up a new to us 2016 19' Jayco Flight and only get hot"ish" water for about 2 seconds then goes cold. Any ideas?

 

[Henry J Fate]

water heater not working.

any idea what water heating equipment is in the trailer ?

 

[Ex-Calif]

We just picked up a new to us 2016 19' Jayco Flight and only get hot"ish" water for about 2 seconds then goes cold. Any ideas?

Hmmm... There should be a pop-off /drain valve on the tank. Be very careful of scalding water but open a drain and check that there is in fact plenty of hot water at the tank.

Next I would investigate any fixtures that have a hot/cold separate tap and also have some sort of deadheading device.

i.e. outdoor shower may have two mixing taps but the shower head has a shutoff. Same in the shower probably. If both taps are open and the supply is deadheaded by the shower head cut-off you could be set up for backflow.

My theory (of course) is that you get a momentary spritz of hot water but then the cold water takes over, back flowing through the hot lines.

 

[Babe2201]

I wonder if the bypass valve is closed. Not sure why you would get any if that is unless it is open just enough to let a little into the water heater.

 

[DutchmenSport]

Do you have a shut off at the shower head in your bathroom, and ... do you have an outside shower on the end of a hose that has a shut-off at the shower head?

If so, make sure the actual faucets are turned off and not left on. When the faucets are left on and shower heads are in the off position, hot and cold water mix and then everything, everywhere comes out luke warm, or sometimes, even cold.

Check that and make sure all your faucets are turned off, hot and cold.

 

[Gary RV_Wizard]

Three common problems with those symptoms would be:

1. The heater bypass is fully or partially engaged so that water is not flowing thru the heater. Make sure the bypass valve is in the correct position for heating water.
2. A shower faucet is turned on but the water shut off at the shower head, allowing cold water to mix with hot thru the faucet. Check the outside shower if you have one.
3. The next most likely cause is similar to #1 above but involves a clogged or stuck check valve at the tank outlet. It happens if the water has a fairly high mineral content (hard water), especially if the system has been sitting unused for awhile.

 

[Rene T]

The next most likely cause is similar to #1 above but involves a clogged or stuck check valve at the tank outlet. It happens if the water has a fairly high mineral content (hard water), especially if the system has been sitting unused for awhile.

I believe he’s getting good flow it just that the hot water turns cold in no time. If it was a bad check valve, he wouldn’t get any water out of the hot side faucets.

 

[John From Detroit]

Most common cause is what I call the "Dog Shower" the outside "Shower" used to rinse the sewer hose and such. you open both hot and cold then close the cut off valve in the shower head.

#2 is the water heater bypass valves. if you have a 3 valve system like I did and open all 3.
(The bypass should be closed)

 

[Gary RV_Wizard]

I believe he’s getting good flow it just that the hot water turns cold in no time. If it was a bad check valve, he wouldn’t get any water out of the hot side faucets.

You are most likely right but there are a few scenarios where cold will flow instead. I didn't want to omit this possibility even if less likely.