Difficult Hot Water Lighting
Two thoughts on possible issues that might cause your pilot lighting problem. The first is the possibility that an insect may be part of the cause - - spiders seem to love building their nests inside the air mixture tube, and this causes the pilot to either be difficult to light or if it lights the burner runs so rich that black soot covers the exhaust of the water heater (the tube can be carefully removed and cleaned with a small, soft bottle brush; and then replaced on the water heater). A second possibility, if this happens primarily after a period of not being used, especially if the propane has been turned off at the main tank valves, it may be air in the lines - - one way that I deal with this on my Overlander is to light all four burners on the range and wait for their flames to stabilize before I try lighting any of my other LP appliances.
It is also a possibility that the burner may need cleaning and adjustment.
Good luck in finding the source of your difficulty.
Kevin D. Allen
WBCCI (Lifetime Member)/VAC/Free Wheelers #6359
1964 Overlander International/1999 GMC K2500 Suburban (7400 VORTEC/4.11 Differentials)
1978 Argosy Minuet 6.0 Metre/1975 Cadillac Eldorado Convertible (8.2 Liter V8/2.70 Final Drive)