Robotic pool cleaner not climbing walls? Fixes to try, cheapest first

Start with the filter. A blocked filter is one of the most common reasons a robot stops climbing, and it's free to fix. After that, check the mode (and the battery on a cordless robot), then brush the walls. Even clear water can leave a slippery film the robot can't grip.

If none of that works, look at trapped air, the cable, the impeller, worn brushes or tracks, and the water temperature, in that order. Everything below comes from the troubleshooting guides Maytronics (Dolphin), Zodiac and Aiper publish for their own robots. We haven't run these robots ourselves, and your manual has the final say.

Is it actually a fault?

Maybe not. Zodiac says a robot on a full floor, wall and waterline cycle often works the floor first and won't climb on every pass. Watch the first 20 minutes. If it never goes up a wall, or keeps trying and sliding back, something's wrong.

Also check yours is meant to climb. Some models only do the floor. Aiper's Scuba V3 is one.

What it's doing tells you where to look

The fixes, cheapest first

1. Clean the filter properly

Maytronics Australia puts dirty filters near the top of its list. The robot holds itself on the wall with suction, and a clogged filter kills it. Rinse the basket, cartridges or bag after every run, and soak them in filter cleaner if oil or calcium has built up.

A filter can look clean and still be blocked. Maytronics says its ultra-fine (paper) filters should wash out white. If one stays brown or green after a hard hosing, it's probably time for a new one.

There are two quick ways to test it. If you run ultra-fine filters, swap to the coarser net filters for one run. If the robot climbs, the fine ones need replacing. On a Dolphin Liberty, Maytronics suggests a 10 to 15 minute run with the filters out altogether. Only do that if there's nothing hard or sharp in the pool, because nothing's protecting the impeller.

While you're there, make sure the filter is seated properly with no gaps. If gum leaves are the problem, our gum-leaf guide explains why fine filters clog so fast.

2. Check the mode and the battery

Zodiac's troubleshooting table for the FreeRider FR350 iQ lists "Floor Only" mode as a cause; switch to Floor/Wall. Maytronics says the same about floor-only and fast modes on Dolphins, whether you set them in the app or on the power supply.

Cordless robots need charge to climb. Aiper says wall climbing on the Scuba X1 uses a lot more power than floor cleaning, so start with a full charge. In pools deeper than about 2.4 m, Aiper says the X1 may not reach the top on one charge and you should run a second cycle. Our cordless vs corded guide covers the battery trade-offs.

3. Brush the walls and test the water

This is the one people miss. Zodiac notes that clear water can still carry micro-algae that make walls slippery. Maytronics Australia's advice for a Dolphin that tries to climb and slips is to brush the wall until the film is gone, then rebalance the water. It also lists high calcium and algae build-up as causes of lost grip.

For home pools, SA Health recommends free chlorine of 1.0 to 3.0 mg/L (ideally 2) and pH of 7.2 to 7.6. Zodiac's own robot advice says pH 7.0 to 7.6. SA Health also says algae on the walls means chlorine isn't being kept up.

4. Let trapped air out

A robot with air inside sits a bit light and can't hold the wall. Maytronics says to lower it in slowly, tilt it side to side until the bubbles stop, and wait for it to sink before you start it. Zodiac's version is simpler: lift it out and put it back in.

5. Give a corded robot enough cable

Too little cable in the water and the cable drags the robot off the wall. Too much and it tangles. Maytronics says the cable in the pool should match the pool's longest dimension. In a 10 m by 4 m pool that's about 10 m of cable, measured from where it enters the water, with the rest left out.

Twists matter too. Maytronics suggests stretching the cable out in the sun now and then, and not winding it tightly around the caddy handle.

6. Clear the impeller

Leaves and hair wrapped around the impeller cut the water flow that holds the robot on the wall. Unplug the power supply first, or switch off a cordless robot. Maytronics says to open the impeller cover with a Phillips screwdriver, not a power drill. Check the side grilles too if yours has them, and follow your manual before you open anything.

7. Check brushes, tracks and climbing rings

These wear out. Maytronics Australia's warning signs are a robot that slides down walls, climbs on and off, spins in place or loses traction, and it says you'll notice it most on smooth fibreglass or tile. Replace flattened brushes and loose or cracked tracks.

If your Dolphin has foam climbing rings on its brushes, leave them on and replace them when they wear. Zodiac recommends new tracks every two years. Aiper says to clear debris off the drive rollers.

8. Check the water temperature

Maytronics says Dolphins should run in water between 6 and 35°C, that cold water can badly affect climbing, and that it should be kept above 15°C. If yours climbs well in summer and struggles in an unheated pool in July, that's probably why.

After a storm

Summer storms in south-east Queensland and northern NSW wash leaves, dirt and algae spores into pools. SA Health says rain and wind bring algae in and a pool may need a shock dose after a storm. If your robot starts sliding off the walls after one, here's how the clean-up works.

Take an 8 m by 4 m pool, 1.0 m deep at the shallow end and 1.8 m at the deep end. The average depth is 1.4 m, so it holds 8 × 4 × 1.4 = 44.8 m³, or 44,800 litres. SA Health's example shock dose is 200 mL of 12.5% liquid chlorine per 1,000 litres, which takes free chlorine to 10 mg/L. For this pool that's 44.8 × 200 mL, or roughly 9 litres.

That's an estimate. Follow the label on your product, because strengths vary. Keep the pump and filter running, as SA Health advises, and always add chemicals to water, never water to chemicals.

Take the robot out first. Zodiac's FR350 iQ manual says not to leave the cleaner in the pool during chemical treatments, and Zodiac advises against running a robot during a shock dose. SA Health says not to swim until free chlorine is back down to 4 mg/L, which can take overnight. We'd leave the robot out just as long.

When the levels are back in range, brush the walls, rinse the robot's filter and run a floor-and-wall cycle. Watch the first 20 minutes. Our pool volume and chlorine calculator will do the sums for your pool, and the Queensland summer pool checklist covers the rest of storm season.

Pebblecrete and tiled pools

The surface makes a difference. Aiper says pebble aggregate and rough plaster give the X1 less grip, and that it works best on smooth plaster, fibreglass and vinyl. Maytronics says brush wear shows up most on smooth fibreglass and tile, and offers a "Wonder Brush" for very smooth surfaces like polished mosaic. It says combined brushes (PVC with foam climbing rings) can help grip, but check with Maytronics Customer Care that your model takes them. Our pebblecrete guide has more on wear from rough finishes.

When to call a technician

If you've been through all eight and it still won't climb, it's a job for a technician. Maytronics Australia says an authorised Elite Dealer can check the motor, drive and electronics. If the robot is under warranty, Zodiac suggests going back to the retailer first, and its Australian manual lists customer support on 1300 186 875. Have the model, serial number and the list of what you've already tried ready when you call.

Quick questions

Is it normal for a robot cleaner to skip the walls sometimes?

Yes. Zodiac says robots don't climb every wall on every pass, because they work the floor first. If it never climbs in the first 20 minutes, or keeps sliding back down, start troubleshooting.