What a Robot Pool Cleaner's Filter Does

Everything a robotic pool cleaner picks up ends up in one place: its own filter. That filter is the part you'll open, empty and rinse most often, so it helps to know what it's doing.

A filter that stands alone

Some pool cleaners hook into the pool's plumbing. Robots don't work that way. One description of electric robotic cleaners says they are independent of the pool's main filter and pump system¹. They plug into their own power source instead.

That has a plain consequence. Nothing the robot collects goes to the pool's sand, cartridge or other main filter. It stays inside the robot until you take it out.

What happens inside

The same description says the robot has two internal motors. One drives the tracks. The other sucks in water through a self-contained filter bag and ejects the filtered water back into the pool¹.

So the water moves through the robot, and the debris stops in the filter. The brushes help too. They direct the particles into the internal filter bag, according to the same source¹.

The word "bag" is just one name. Makers use other wording for the part that holds the debris. One maker's instructions for a robot call it a dual filter basket, with a latch that opens a bottom lid to remove the debris².

Why it fills

Whatever the robot picks up has to stay somewhere. Whatever the robot meets all lands in that one space. A full filter has nowhere left to put more.

The same Wikipedia article makes a similar point about cleaners that use the pool's plumbing. Large amounts of debris, or larger debris such as leaves and sticks, can easily clog the unit or its pump basket¹. That sentence is about a different type of cleaner, but the idea carries over: a filter holds only so much.

What the maker says to do

For the robot in that manual, the guidance is short. The maker highly recommends cleaning the basket after every cleaning cycle². Your own model's manual may say something different, so check it.

You'll find the steps for taking a filter out on the page about emptying the filter. Rinsing is covered on its own page, and the question of timing is on how often to clean.

A quick way to picture it

Think of a coffee filter, or the lint trap in a clothes dryer. The robot moves water, the filter holds what's left behind, and when it's full the flow suffers. That comparison is only an image. The manual for your own robot is the real guide to what's inside it and how it opens.

Before you open anything, switch the robot off and unplug the power supply. The Dolphin instructions put that first in the cleaning section².