Why Grill Pellets Absorb Moisture

A wood pellet is sawdust pressed into a hard stick. Water undoes that. Add a little, and the pellet puts the sawdust back.

What a pellet is made of

Grill pellets are compressed wood. Pellet fuel in general can be made with a low moisture content, below 10%¹.

Some pellets contain nothing but wood. One maker notes that its pellets are 100% natural and have no artificial fillers, so moisture can expand the wood and make it crumbly². The maker doesn't say all pellets from every brand behave the same way. Check your bag and your manual.

What moisture does to them

Wikipedia puts the effect plainly: when small amounts of water are added to wood pellets, they expand and revert to sawdust¹. No special soaking is needed. A little is enough.

What's left is a soft, crumbly lump or a pile of dust.

Where the water comes from

Rain is the obvious source, but it isn't the only one. Damp air can do the job too. Materials that pull moisture from the air are called hygroscopic, and Wikipedia says such materials might require storage in sealed containers³. That page describes the general idea. It doesn't single out wood pellets, so treat it as background, not a rule for your bag.

One pellet maker says moisture can seep even into unopened bags kept in a garage in a humid region². So a sealed bag isn't a guarantee on its own, and where you keep it counts. Ways to guard against that are covered in the storage advice and the container comparison.

Dry pellets, in numbers and in the hand

Wikipedia says pellets are extremely dense and can be made with a moisture content below 10%¹. That figure is the starting point. Damp air or splashes push the pellet away from it.

Different brands may start at different moisture levels, and the page gives only the general figure. A bag's label or the maker's site is where to look for a specific product's number.

Why it matters in the grill

A pellet grill feeds fuel with an auger, a slowly turning metal screw. It pushes pellets from the hopper (the box that holds them) to the fire pot. The auger works well on hard, dry pellets. It struggles with mush.

Traeger's page warns that crumbly pellets can clog the auger and may fail to ignite². Z Grills' support page names a second problem. Wet dust in the feed tube can gradually set like wood concrete⁴. The same page shows dry pellets next to wet and swollen pellets, and the difference is easy to see⁴.

The symptoms differ by model, so your manual is the place to look for your own grill's. The later pages on this site cover spotting damp pellets and clearing them from the hopper.