Robot cleaners on plaster and concrete pools

Concrete pools are finished inside with some form of concrete, often called plaster, and the surface is rough. That roughness helps a robot in one way and costs it in another. Here's the trade.

What the finish is

A builder's guide says the interior surface of a concrete pool will be some form of concrete. It lists names such as pool plaster, marbelite, marcite and pebble finish.¹

Grip: the upside

A maker says concrete and gunite pools have a rough, porous texture that gives track wheels strong traction.² Another maker says vertical concrete walls are heavier going than fibreglass, and a cleaner with weak traction slips back down before it reaches the waterline.³ So grip still counts, even on a finish that offers plenty.

Wear: the cost

The same texture wears brush bristles faster over time.² A second maker says rough or textured concrete may need a cleaner with suitable traction and durable brushes.⁴ And some concrete pools may have rough or uneven finishes that make movement and coverage harder.⁴

Flat or frayed brushes are wear you can see. Your manual should say when to replace brushes and tracks, so follow that for your model.

Dirt in the pores

Pores are tiny holes in the surface. One maker says fine debris and algae settle into concrete's surface pores.²

Both sides of a rough finish

Put the makers' points side by side. Texture gives tracks strong traction.² Vertical walls are still heavier going than on fibreglass.³ Brushes wear faster, and fine debris settles into the pores.² None of this means a robot can't work here. It means the manual's notes on rough surfaces are worth reading first.

What to check

Makers write about pools in general terms, so your own manual is the better guide for your model. If it says nothing about concrete, plaster or gunite, ask the maker before you rely on any of the points above.

• Read the manual for a plaster, concrete or gunite mention, or a rough-surface note.
• Look for a brush or track option the maker pairs with rough finishes.
• Check the parts for wear. Replace them as the manual says.
• Note any spots where the robot slips or stalls. A pool can be concrete underneath and still have a different finish on top. A vinyl liner can hang inside a concrete shell, for instance. If you're unsure what you have, this guide to telling surfaces apart helps.

Pebble finishes are rougher again, and have their own page. The general ideas are in an overview of surfaces.

Nobody swims while the robot runs. Follow the manual for power supply rules near water.