Glassbird, Are you sure that there is no access panel in the floor above that water heater where the connections are? It seems like there has to be some way to get at those threaded fittings. What is above where the water heater is? If you had to replace the water heater, how would that be done? I think that as jimbo12 suggested, you might want to consider a repipe with PEX in the future. If it is possible to get those hoses disconnected from the water heater then you might want to assemble new plumbing in that compartment using PEX. You could preassemble it how you want with all the fittings and bypass in your garage and then install it as a unit. If you could access the piping in other areas outside of that cramped compartment then you could cut and splice the plumbing in those areas. I know this is a little off the original question but if you’re going to modify and improve that plumbing you might want to just change it out while you’re at it.