Hot water heater

Purge the line....
Light a stove burner or two, this will get the air out of the lines and get propane flowing to your water heater.

Also if the line was not pressured and you opened the tank valve fast the overflow protection device can limit the flow.

I tried the running burners on the stove . They worked fine but not the hot water heater. It doesn't even sound like it's trying. If it was pressure ...what's the remedy?

Might have "locked out" due to too many tries.
Depending on your unit...Try pushing the RESET button on the back of the heater.

EXAMPLE:

Those reset buttons^^^^^^^^^^ are to reset the HIGH Temp T-stats nothing to do with 'lock out'
High temp t-stats trip at 170*F/manual reset
Left side 120V AC...electric element
Right side 12V DC...propane

'Lock out' happens when 3 attempt to light flame and prove it lit fail
'Lock out' will trigger the RED Fault Light on switch panel
Reset by turning ON/Off Switch OFF---wait 30 seconds then turn on

IF spark electrode is not 'firing' then it could be a 12V DC issue
The 12V DC set of t-stats are connected via a wire from top t-stat to bottom t-stat...they can burn into
Could be connection inside junction box on backside of WH Tank
Could be an issue with the circuit board on backside of WH Tank or mounted close by

So you need to test where you have DC and NOT have it




IF you do have 12V DC then.....
Keep trying to light water heater
LP System is only 0.4 psi....can take several attempts to get full flow to all appliances

Ditto on what Old Biscuit said, which is a very detailed and thorough post.

The red DSI switch never comes on at all (since this started). I can’t even hear the hot water heater trying to ignite

kramer45011 wrote:
The red DSI switch never comes on at all (since this started). I can’t even hear the hot water heater trying to ignite

Then you have a DC Voltage issue

Get out the Voltmeter and start tracing the DC from On/Off Switch to gas valve.

Already posted 12V DC circuit so use it.

Is there a possibility it could be a fuse?