I live in a mobile home I don't have hot water pressure the water heater is new they tell me there is lime in the elbows and other tees they say I need to pressurise the line to dislodge the line do I presurrise it with air or water and how much pressure

If they tell you this, then they should be able to explain how they have done this on previous jobs. And if they have done this with successful results, then please let me know how they do it. Sure would be a lot easier than replacing the clogged fittings.

Who is the "they" I am pretty sure they aren't plumbers. How long since you flushed the heater? Do not pressurize your plumbing with air pressure.