How to find out what your pool surface is

Start at the top edge of the pool wall, then touch the surface. Three quick checks tell you a lot. Check your robot's manual surface list against what you find.

Check one: the top edge

One builder's guide calls the liner the easiest to spot. It needs a coping track to hang from.¹ Look along the pool edge. Is there a strip or lip where the liner tucks in? If so, you likely have a liner.

Check two: press the wall

On the same guide, fibreglass interiors on concrete pools are hard to the touch, while membranes and liners give slightly.¹

Check three: smooth or rough

Fibreglass pools have a gel coat finish, which one builder calls non-porous and smooth.² An in-ground fibreglass pool is a one-piece shell.³ A concrete pool's inside is some form of concrete, which can go by names such as plaster, marbelite, marcite or pebble.¹ A pool builder describes an aggregate finish as small pebbles, stone or glass in the surface.² If you see bumps of stone, you probably have an aggregate finish. For that case, see pebble and aggregate finishes.

Shell and surface can differ

The shell is the structure. The surface is what the robot touches. They don't always match.

• A concrete-shell pool with a vinyl liner inside counts as a vinyl liner pool, because the guide says the liner is the interior surface.¹
• A fibreglass skin can be applied inside a concrete pool, so the surface is hard but the shell is concrete.¹

For a robot, the surface is what counts. Plaster, liner and gel coat each wear and grip differently, and each has its own guide. Read the one for a liner, for a gel coat or for plaster.

A short piece on what the finish does to a robot explains why this matters in the first place. It's worth ten minutes before the first run. A wrong guess here means you'd follow the wrong advice for your robot.

If it still isn't clear

None of these checks is a test that proves the answer. They are starting points. Write down what you see at the edge and on the wall, so you can show it to a pool professional or to your robot's maker.

The same guide warns that paint and membrane coatings can look alike, and that thicker paints might resemble a membrane in look and feel.¹ Where you can't tell, look for the paperwork from the build or ask the pool's builder or a local pool professional. Then check that surface against your robot's manual before you run it.

When you do run the robot, nobody should be in the pool, and your manual's rules on power supplies near water come first.