Automatic Pool Cleaners: Suction vs Pressure vs Robotic

Three kinds of automatic pool cleaner are sold, they work on entirely different principles, and the cheapest to buy is often the most expensive to own. The right choice depends less on the cleaner and more on your pool: its shape, its surface, and how much your pump costs to run.

Suction-side cleaners

A suction cleaner connects to the skimmer or a dedicated suction port and is driven by the pump pulling water through it. It has no motor of its own. It wanders the pool semi-randomly, and whatever it picks up goes into the pump basket and then the filter.

What it does well: it is the cheapest to buy, usually by a wide margin, and it has almost nothing to break. Many have a single moving part. It picks up fine debris well because everything goes through the filter, and it works on any surface.

What it does badly: everything it collects ends up in your filter, so the filter clogs faster and needs cleaning more often. It requires substantial flow, which means the pump runs harder and longer while it operates. It struggles with large debris, which blocks it. And it reduces suction at the skimmer while connected, which means surface skimming suffers exactly when leaves are falling.

On a vinyl pool a suction cleaner is gentle and generally a good match. On a large pool with trees it becomes a source of frustration.

Pressure-side cleaners

A pressure cleaner runs off water returning to the pool rather than water being drawn out. It has its own collection bag, so debris never reaches the filter, and many need a separate booster pump.

What it does well: the debris bag is the significant advantage. Leaves, acorns and grit go into a bag you empty rather than into a filter you have to backwash, which meaningfully reduces filter maintenance and water waste. It handles large debris far better than a suction cleaner. It also returns filtered water through the unit, which helps circulation.

What it does badly: fine dust is left behind, because the bag mesh cannot catch what the filter would. Many models require a booster pump, which is more equipment to buy, install and run — and a booster pump is a meaningful addition to the electricity bill. Installation is more involved, usually needing a dedicated return line.

Pressure cleaners suit large pools and pools surrounded by trees, where bulk debris is the real problem and fine dust is secondary.

Robotic cleaners

A robotic cleaner is an independent machine. It plugs into a standard outlet, has its own motor, its own filter cartridge and its own drive system, and it works whether or not the pool pump is running.

What it does well: it is comprehensively the best cleaner of the three. It filters to a finer level than most pool filters, it scrubs rather than merely collecting, most models climb walls and clean the waterline, and better ones map the pool rather than moving randomly. Because it is independent of the pump, it costs nothing in pool-pump electricity — a robot typically draws under 200 watts against the several hundred a booster pump adds.

What it does badly: it is the most expensive to buy, often by a factor of two or three. It is a machine with electronics in a wet environment, so it will eventually need repair, and repairs are rarely economic on cheaper models. It has to be lifted in and out, which is a genuine consideration if it is heavy and you are not. And the cable can tangle, though swivel designs have largely solved this.

Comparing the three

The running cost row is the one that changes the arithmetic most and gets the least attention at the point of sale. A pressure cleaner with a booster pump running three hours a day can add more to a season’s electricity than the price difference between it and a robot.

What your pool should decide

Shape. A simple rectangle suits any cleaner. A freeform pool with tight curves, benches and a tanning ledge defeats randomly navigating cleaners, and a robot that maps the pool is worth considerably more there.

Surface. Vinyl liners want gentle brushes and no aggressive scrubbing. Plaster and pebble tolerate and benefit from harder brushes. Most manufacturers specify which surfaces a model suits, and ignoring it can damage a liner seam.

Debris type. Fine dust, pollen and silt point to suction or robotic. Leaves, acorns and twigs point to pressure or robotic. If you have both — a pool under trees in a dusty region — a robot is the only one that handles both well.

Depth and steps. Deep pools with steep slopes defeat some cleaners entirely. Steps and swim-outs are where debris collects and where most cleaners never go, so expect to brush them by hand regardless of what you buy.

Your pump. If you have a variable-speed pump and have carefully tuned it to run slowly, a suction or pressure cleaner forces it back up to high speed while it operates, which undoes part of the saving. A robot leaves that schedule alone entirely — see variable-speed pump payback.

What no cleaner does

Worth being clear about, because expectations are often set by marketing.

• No cleaner replaces brushing. The places algae starts — steps, corners, behind the ladder, the waterline — are precisely the places cleaners miss. Weekly brushing remains part of the routine.
• No cleaner replaces skimming. Cleaners work on the floor and walls. Floating debris is a skimmer and a net.
• No cleaner fixes chemistry. A cleaner removes what has settled; it does nothing about what is dissolved.
• No cleaner replaces filtration. Water still has to turn over — see how long to run a pool pump.
• No cleaner cleans a green pool. Clear the algae chemically first; running a cleaner through a bloom just spreads it and clogs the unit.

Total cost over five years

Purchase price is the number people compare and the least useful one. A rough five-year picture for a typical US in-ground pool looks quite different.

A suction cleaner is cheap to buy and needs occasional diaphragms and hoses. Its real cost is the additional pump running time it demands and the extra filter cleaning it causes — neither of which appears on a receipt.

A pressure cleaner with a booster pump adds a second motor running several hours a day. Over five seasons that electricity frequently exceeds the entire purchase price of the cleaner.

A robot costs most upfront and least to run, but a failed motor or gearbox at year four can write it off, because repair costs on mid-range models often approach replacement. Warranty length and the availability of spare parts matter more here than with either alternative.

The honest summary: on a pool where the pump is expensive to run, a robot usually wins over five years despite costing most to buy. On a small pool with cheap electricity, a suction cleaner is hard to beat on total cost.

Making one last

• Do not leave it in the pool permanently. Continuous chlorine exposure degrades seals, hoses and brushes. Take a robot out after each cycle.
• Rinse a robot with fresh water after use and let it dry out of direct sun.
• Empty the bag or cartridge every time. A full collection chamber means the cleaner is moving debris around rather than collecting it.
• Check brushes and tracks annually. Worn brushes stop scrubbing long before they look worn out.
• Store it indoors over winter. Freezing damages hoses, seals and electronics.
• Keep the pool’s water balanced. Aggressive water attacks cleaner components as surely as it attacks a heater.

Where a cleaner fits in the routine

A cleaner is a labour-saving device rather than a maintenance strategy. The routine it fits into is unchanged: test twice a week, brush weekly, empty baskets weekly, keep the water turning over, and clean the filter by pressure reading rather than by calendar. Our maintenance guide covers the full rhythm.

What a cleaner buys you is the vacuuming — typically the most tedious hour of the week — and it does it more consistently than most people manage by hand. That is a genuine benefit, and it is worth paying for. It is simply not the same thing as looking after the pool.

Troubleshooting a cleaner that has stopped working properly

Most cleaner faults are not faults at all. Before assuming a unit has failed, work through these, because the cause is usually elsewhere in the system.

A suction cleaner that has slowed or stopped is nearly always a flow problem rather than a cleaner problem. Check the pump and skimmer baskets, check the filter pressure against its clean baseline, and check the hose for splits — a hairline crack in a hose lets air in and destroys suction without being obvious. Air bubbles returning to the pool point to the same thing.

A pressure cleaner that will not move usually has a blocked jet or a worn drive belt. Check the bag first: a full bag stops the unit as effectively as a mechanical fault, and it is the thing people forget.

A robot that climbs walls but misses the floor, or the reverse, generally has worn brushes or tracks. Brushes stop gripping long before they look worn out, and replacing them restores behaviour that owners often attribute to the unit ageing.

Any cleaner that gets stuck in the same place is usually meeting a pool feature it cannot negotiate — a steep slope, a main drain cover that catches, a tight radius. Hose length set incorrectly is the other common cause on suction and pressure units.

One check worth doing before any of that: is the water balanced? Aggressive water degrades hoses, seals and plastic parts steadily, and a cleaner that has aged unusually fast has often been swimming in water that was corroding it. See calcium hardness.

Vacuuming by hand, and why it still has a place

Every pool owner should know how to vacuum manually, even with a cleaner, because there are jobs no automatic cleaner does well.

The most important is vacuuming to waste. Dead algae after a shock treatment, or a heavy layer of fine silt, should not go through the filter — it will clog it immediately and much of it will pass straight through and return to the pool. Vacuuming to waste sends it out of the system entirely, bypassing the filter. It costs water, and it is the fastest route to a clear pool after a bloom.

Manual vacuuming is also the answer for steps, benches, swim-outs and tight corners — the places cleaners consistently miss and where debris consistently collects.

The technique is unremarkable: submerge the head and hose to fill it with water and expel the air, connect to the skimmer with the basket in place, and move slowly in overlapping passes. Moving quickly stirs debris back into suspension and undoes the work. The EPA’s WaterSense programme is worth a look if you are weighing the water cost of vacuuming to waste against the alternative.