Fine Silt and Dust on the Pool Floor

Fine dirt is hard to hold. Silt and dust are tiny. Whatever is smaller than the filter's openings goes straight through.

Why a film can stay behind

A robot collects dirt by drawing water through a filter. If the dirt is smaller than the mesh openings, it can pass through and return to the pool. Settling then puts it back on the floor.

Older cleaners share this limit. A reference page says they can't pick up particles finer than their filter's pores¹. A robot is separate from the pool's main filter and pump¹. So the limit moves to the robot's mesh.

What ultra-fine filters are for

Maytronics says an ultra-fine cartridge holds smaller particles, fine silt among them². It calls that filter important for pools with green water or fine debris².

A finer mesh isn't free of cost. The page says a clogged filter cleans less well². If the mesh clogs, the robot is cleaning less, however good the mesh is.

The order of filters

Some robots carry two filters. Maytronics says to make sure the debris passes the coarse basket before the ultra-fine filters, and it warns that some models place the ultra-fine filter first². Your manual shows which way your model is built and how the parts fit.

Keeping a fine filter working

One maker's support page treats two signs as a prompt to open the basket: dirt in it, or a cleaning result that isn't satisfactory³. The same page says to air-dry the filter mesh and filter basket before putting them back into the robot³.

Maytronics adds a rinse under a garden hose until the water runs clear². That's its advice for its own filters. Follow your manual for the right way to clean yours.

What to expect

• Fine dirt can stay in the water after a run.
• A finer filter holds more of it.
• A clogged one cleans less.

The robot is one part of the picture here. Leaf-sized dirt behaves differently, as the page on big debris explains. For the broad view, start with the basics of what gets collected.

Rinse the mesh gently and let it dry. A damp, dirty mesh won't do its job on the next run.

If you can't tell whether a film on the floor is fine dirt or something growing, a pool shop can look at a sample of the water with you. The robot's manual won't settle that question, and the sources saved here don't either.

If the water looks cloudy or green, that's a water-care question. Your pool shop, or the maker of your pool's own equipment, is the right person to ask.