REasley
Adventurer
Other than the price... I got the hot water unit for the same price as a on demand pump. That being said, I may replace the pump with an RV unit if I can't figure out how to hook up the pump to my bulk tank. I wouldn't use an on-demand unit though. I'll use the power supply from the Coleman system.
I am using the same Coleman unit on my trailer. I have not disasembled the Coleman pump, but it looks to be a centrifugal. and must have a flooded suction or or be submersed. Since my tank is mounted in the frame and has a very low profile, the Coleman pump won't work very well. I am using a Shurflo demand pump. I'll simply wire around the switch. That makes it open flow and will only build pressure based on the friction thru the water heater. I will measure the flow with the original pump and then select a pump that closely matches.
As to cost, Shurflo RV pumps if purchased thru an RV supplier have a high margin. You can buy an AG pump from a farm supply store for a lot less. The pumps are the same with the exception of the valves. The RV version uses EPDM valves and the AG version uses Viton. You can find these pumps for under $50.00