Dobby's Dirt Disposal Bag

I bought an iRobot i3+ Roomba with Clean Base Automatic Dirt Disposal in January of 2023.

Clean Base Automatic Dirt Disposal

An iRobot Clean Base Automatic Dirt Disposal is a charging base with a vacuum attached:

Roomba on a “clean base” charger/vacuum

Here’s iRobot’s illustration of how the vacuum works. It also shows where the vacuum bag I mean dirt disposal bag lives.

Roomba on a “clean base” stand, cutaway to show vacuum

The Clean Base that Dobby rolls up on has an orifice that matches the green rubber flap on the lower left of Dobby’s underside in this view:

Roomba i3+ robot on its back showing its undercarriage details

The Clean Base runs a an air compressor that draws air through the dirt disposal bag. The compressor draws hard enough to suck open the rubber flap, and empty Dobby’s internal dust and detritus reservoir. I believe this airflow is the reverse of airflow during vacuuming, some of the finer dust caught by Dobby’s HEPA filter gets pulled out as well.

Dirt Disposal bag details

After about 26 months of not-entirely-satisfying use, I just changed the dirt disposal bag for the second time. The iRobot “App” said that the dirt disposal bag was full. It apparently decides this by the time Dobby spent vacuuming. Here’s the dirt disposal bag.

iRobot dirt disposal bag with apple for scale

Apple for approximate scale. I didn’t have any bananas around for accurate scaling.

An empty dirt disposal bag weighs about 30 grams, and is roughly 5x5x6.5 inches in size. The dirt ingress hole is 1.25 inches in diameter.

Outer bag seams look fused rather than sewn. The material, which is not air-tight, is some kind of woven, or more likely felted, plastic fiber. It has two layers, an inner, coarser woven (or felted) bag, and an outer finely woven bag. Some dust escapes through the inner bag into the liminal space between inner and outer bags.

dirt disposal bag with outer bag cut away exposing inner bag

Dirt Disposal Bag dirt

The full bag weighs 98 grams. That means 68 grams of dirt and detritus collected during 25 hours of vacuuming, at a rate of 2.7 grams/hour.

Dirt disposal bag contents

Dobby doesn’t only ingest USB cables. In additions to dust-bunny like accretions of dirt, hair and otherwise unidentifiable short fibers, the dirt disposal bag contained a paperclip, a short wood screw, a chickpea, pieces of Christmas tree ornaments, and a small loop of wire.

Dyson Ball vacuum dirt

How does Dobby rate in comparison to a real vacuum cleaner? I alternate weeks vacuuming with Dobby. I have a Dyson Ball Animal 2 Upright Corded Vacuum Cleaner. I did not empty the collection chamber from 2026-02-21 to 2026-04-16, almost exactly 2 months. The Dyson collected at least 47.4 grams of dust, flotsam and jetsam.

During those 2 months, I ran the Dyson 4 or 5 times in the same house, on the same floor as I ran Dobby. Each session lasted between 45 and 60 minutes. That’s a dust collection rate of between 9.5 and 15.8 grams/hour. The Dyson is far better than the Roomba in terms of dust collected per hour.

Contents of Dyson Ball dust collection chamber

The Dyson’s collection looks very similar to Dobby’s. Dust bunny accretions of fine, short fibers and larger dust. It has a greater admixture of hair than Dobby’s collection. There’s also a high proportion of very fine dust. The Dyson doesn’t capture as many larger items, like Dobby’s screw, paperclip and chickpea.