On Alpamayo we recommend you take a good purifier the Katadyn is a favourite though we've had good luck with many other units.
Make sure your purifier is well maintained. They need frequent cleaning.
Campsites
There are official campsites on Alpamayo with very nice signage. But you can camp anywhere you like.
If you choose to camp near people, ask permission.
There is no cost for camping. At least we were never asked for any payment. (We had no pack animals.)
Our recommended route does specify where we think you could stop each night.
E-mail us with any alternative camp site recommendations.
Cooking
All cooking should be done on a lightweight camping stove. Bring a back-up stove if possible, in case your primary stove breaks down.
Fuel for almost any stove is available in Huaraz.
Meals should be as simple & quick-cooking as possible. Instant mashed potatoes are a staple in South America. We rehydrate in soup rather than water.