Sand and silt is the debris type that exposes bad machines. Leaves are forgiving: almost anything with suction and a basket moves them. Fine sediment is not. If the mesh is coarser than the particle, the particle goes in the intake and out the exhaust, and all the machine has done is lift your sediment into suspension so it settles somewhere else.
That is why “it just pushes the sand around” is the single most common complaint in this category — and it is not a navigation problem or a suction problem. It is a filter rating problem.
Read the micron number, and notice who does not publish one
A micron is a thousandth of a millimeter. Pool sand is coarse — often 100-500 microns — so a 180-micron basket catches some of it. Silt, pollen, dead algae and the fine fraction of windblown dust are in the 1-30 micron range, and a 180-micron basket catches none of it.
Here is where the published figures actually sit:
- 3 micron — Aiper Scuba X1 Pro Max, Aiper Obsidian. Catches essentially everything, blinds fast.
- 10 micron — WYBOT C2 (fine layer, with a 180-micron coarse layer over it). The best fine rating under $500.
- 150 micron — Beatbot Sora 10. Excellent for leaves, wrong for silt.
- 180 micron — Aiper Scuba S1 and SE baskets, most budget machines.
- Not published — a surprising number of popular models, including some flagships. We say so on their pages rather than guessing, and for this debris type an unpublished figure should be treated as a no.
The filtration explainer goes deeper into what these numbers mean in practice.
The dual-layer design is the right architecture
A single 3-micron filter in a real pool blinds within one cycle, because leaf fragments and hair plug the mesh long before sediment fills the basket. The WYBOT C2’s approach — a 180-micron coarse layer in front of a 10-micron fine layer — is the correct engineering answer: the coarse layer protects the fine one, so the fine one keeps flowing. If you are buying for sediment, prefer a machine with a staged filter over one with a single very fine element, even if the single element has a better headline number.
Technique matters as much as the machine
- Let it settle first. Run nothing for several hours. Sediment in suspension cannot be collected; sediment on the floor can.
- Slow passes. A fast-moving robot generates a bow wave that lifts sediment ahead of the intake. Most machines with a “fine” or “intensive” mode are simply slowing down, and that mode is the one to use.
- Rinse after every run. A fine filter full of silt has no flow. Rinsing it between runs is the difference between the machine working and not.
- For a defined patch, use a handheld. Nothing beats parking a hand vacuum directly on the sand. The full sand-removal method is here.
Where the sand is coming from
Worth checking before you buy anything. If you have a sand filter and you are finding sand on the pool floor in a cone near a return jet, your filter’s laterals are cracked and the filter is feeding sand into the pool. No cleaner will solve that — it will just keep removing sand forever. Fix the filter first.
