Can I drink the water?

Yes, the water in the mountain streams of Patagonia is generally pristine and safe to drink without filtering.

Do I need to carry a tent?

Only if you are doing the 'O' circuit in Torres del Paine. If you are doing the 'W', you can book pre-set tents or bunk beds in refugios.

How to Backpack Patagonia in 3 Weeks

Spend three weeks focusing on the 'Big Three' parks: Torres del Paine in Chile, and Los Glaciares (El Chaltén) and Los Glaciares (El Calafate) in Argentina. Use buses as your primary transport and book your campsites or hostels at least four months in advance if you are traveling between December and February.

Secure the logistics early. Book your international flight into Santiago (SCL) or Buenos Aires (EZE), then book regional flights to Puerto Natales (PNT) or El Calafate (FTE). Do not attempt to rely on buses for the entire journey from the capital cities; it takes 30+ hours.
Map out your route. Start in Puerto Natales for the Torres del Paine 'W' trek (4-5 days). Cross the border to El Calafate (3 days) to see Perito Moreno Glacier, then finish in El Chaltén (7 days) for the best day-hiking in the region.
Pack for four seasons in one day. Patagonia wind is legendary. Carry a hard-shell waterproof jacket, a synthetic down mid-layer, and sturdy broken-in hiking boots. Do not bring cotton; it will stay wet for days.
Master the border crossing. The bus from Puerto Natales to El Calafate is the most common crossing. Keep your PDI (immigration paper) from Chile in your passport at all times; you will be fined or delayed if you lose it.

Can I drink the water?: Yes, the water in the mountain streams of Patagonia is generally pristine and safe to drink without filtering.
Do I need to carry a tent?: Only if you are doing the 'O' circuit in Torres del Paine. If you are doing the 'W', you can book pre-set tents or bunk beds in refugios.