I have an older model Laars Lite 400K BTU propane spa heater that uses a pilot light/flame - rather than electronic ignition. I had my 120 gallon tank filled about two months ago and lite the pilot to get ready for the cooler nights. I just noticed I am down to about 1/4 full. I have not used the heater yet. I checked for leaks with soapy water and see nothing leaking at the tank or connection to the heater.

How much gas should used just keeping the pilot flame burning?

It looks like I went through close to one hundred gallons of propane in 2 months (about 1.5 gallons a day) without firing up the heater.

Is this to be expected or do I have a leak somewhere?