Most rucksacks won’t be waterproof (unless there are no seams or zips) but there are several thing you can do to help keep your backpack and its contents dry.
Rucksack liner
A rucksack liner is a large bag with sealed seams that goes inside your rucksack before your kit is put in. A rucksack liner is best used in conjunction with dry bags to separate out kit. Can’t find a rucksack liner? Heavy duty compost or bin bags can be used instead. Check there are no holes in the bag and be cautious when packing sharp objects!
- Dry bags
Dry bags are commonly used for kayaking, canoeing and other extreme sports where there is the chance your backpack will be fully submerged under water. These bags seal tightly at the top and have fully taped seams to keep everything watertight.
If you allow enough air into them they also act as a great buoyancy aid – another reason they are ideal for canoeing. They come in a variety of sizes which make them great for splitting up your kit to help you pack more efficiently.
- Ziplock bags
Ziplock bags can be used to keep smaller items dry. They are most often used for phones, cameras and cash. As ziplock bags are clear you can often still use your phone whilst they are kept in the bag, useful if it is raining. Make sure there are no holes in the bag and they are fully sealed.
- Raincovers
A rain cover goes over your backpack and gives your bag some water resistance – enough to keep your kit dry should it rain (unless it’s really heavy rain). Larger rucksacks will come 
with a rain cover attached but are easy to obtain if not. They are generally elasticated around the edge to ensure that your bag is kept completely covered.
- Proofer Sprays
In the same way you might re-proof a waterproof jacket; waterproofing sprays are available for rucksacks. Although they will improve the fabrics water resistance it’s important to remember that no spray will make your rucksack 100% waterproof as water can still leak through the seams and zips.
