The phrase "a main supply" is correct and usable in written English.
It can be used when referring to a primary source or provision of something, such as resources or materials.
Example: "The factory relies on a main supply of raw materials to maintain its production levels."
Alternatives: "a primary supply" or "a principal supply".
Kosovo is widely believed to be a main supply and transit route for the rebels.
Golf Company's firebase was an old Baath Party hotel near a main supply route to Jordan and Syria.
Most civilians fled from around this town, the regional capital and a strategically important point because the area was a main supply route for Eritrea's westernmost front.
The air corridor over Iraq has emerged as a main supply route for weapons, including rockets, antitank missiles, rocket-propelled grenade and mortars.
Interruptions of energy supply -- a plant's unexpectedly going off line, for instance, or a main supply line breaking down -- can usually be handled by tapping into energy reserves, which all power grid operators are required to maintain.
In April 2009, about 150 militants used rockets and automatic weapons to set fire to eight cement trucks at a transport terminal outside Peshawar, Pakistan, that is on a main supply route used by United States and NATO troops.
To correct this problem, you'll probably need a new main supply pipe going from the meter to your house.
Fearing a breakthrough, Hoge warned out the 27th Brigade, as the corps reserve, to establish defensive positions north of Kapyong on the afternoon of 23 April as a precaution in the event the South Koreans were unable to hold, tasking them with blocking the two approaches to the village and to prevent the Chinese from cutting Route 17, a key route south to Seoul and an important main supply route.
By early 1978, the songwriting was starting to spread among the band, although it was always as a supplement to the main supply from John.
After attacks on convoys that killed five Americans this week, a sixth soldier was killed today, military officials said, when "hostile fire" was directed at a convoy on the main supply route from Kuwait near the town of Anaconda.
According to Wellington City Council, staff worked all night on Friday to find a leak affecting the main supply pipe to Wellington City.
