We had the Girard tankless water heater on our 2013 Wildcat. We really enjoyed it in the months that were cooler, buy cooler I mean that the water coming into the RV was cool not the ambient outside temp. Once the summer temps warmed up which in effect conducted warmer to hot temps to the ground around the buried water pipes meaning warmer water entering the rv and tankless water heater it became much more difficult to control a constant water temp in the shower.
We had to take the Wildcat in for an unrelated issue at the Wildcat Warranty Service Center in Elkhart and mentioned this problem. I told them I was aware to make sure there was absolutely no air in any of the water lines and the manufactures procedures to operate the system and helpful hints on correcting this matter.
Wildcat contacted Girard who said there was a retro fit kit that could be installed and in most cases took care of the situation. However, Wildcat also offered to replace the water heater with a new tank heater that would run on both electric and gas. We accepted that offer and are pleased that we did. We have not run out of hot water during a shower and have be able to maintain a nice even temp of water flow. As an added bonus we seldom use the gas when calling on hot water using the electric most of the time and allow the campground to pay the cost to heat the water.
2018 Berkshire XL 40B
Past RVs: National Pacifica 40', Kenworth T300 Toterhome, Jayco Class C 32'. American Eagle 40',
American Eagle 40', Bounder 38' tag axle