I would think they would be mandatory. Since they are the least likely to burst.
Supply lines
Flush the lines from a clean potable water supply
they can, especially the smaller lines from a water softener, I think you need to get more specific
it dosnt come on
Water supply projects are vital for provision of water but they must be well planned and separated from sanitation pipes lines or system used for disposal of used water
May indicate rust from galvanized pipe feed lines or dirt in water supply.
Mechanical
http://wiki.answers.com/Q/Different_types_of_Stresses_acting_on_water_supply_pipe_lines"
A leak on the return or supply lines and the automatic feeder is not working
That depends on the pressures you are running off the Engine and the G.P.M your achieving at the business end? Theoretically, you would need a 3 inch supply line too supplement two 1.5'' lines,You need to put in enough water supply to achieve the output of water, unless your utilizing tank water.
New Water heater. Faucet and sink drain line repair parts. The sinks, commodes, house and yard water supply lines. Sewer lines
Yes, its preferred.