Pool equipment: how to choose each item and what to base it on

The flow figure on the pump's data plate applies at a specific head; if the pipe run is long and there are many elbows, the real flow drops. That is why, when choosing a pump, you look at the flow-pressure curve and not just the cubic metres per hour figure.

Variable-speed (inverter) pumps spend most of the day at low speed and cut consumption considerably. A fixed-speed pump is either at full power or off. The upfront cost is higher and the payback shows up on the electricity bill; if you run the pool every season, it makes sense.

Check the size of the pre-filter basket too. A pump with a small basket clogs often in gardens with a lot of leaves, and each time the pump has to be stopped and cleaned. For pools under trees, this detail decides how much daily upkeep you face.

An undersized filter leaves the water cloudy, while an oversized one wastes extra water during backwashing.

Using filter glass (crushed glass) instead of silica sand as the media gives finer filtration and reduces backwash water. Its upfront cost is slightly higher, and it lasts longer than sand. To switch a sand filter to glass, you do not need to replace the tank, only the media.

Cartridge filters are used in small pools and hot tubs; they use no backwash water, the cartridge is rinsed instead and replaced periodically. Diatomaceous earth (DE) filters give the finest filtration, but their maintenance is laborious and they are rarely chosen for residential pools.

Disinfectant (chlorine or bromine based) keeps the water microbiologically clean. pH adjusters (pH increaser and reducer) keep the water's acid balance in the 7.2 to 7.6 range. Algaecide prevents algae from forming. Clarifier (flocculant) binds small suspended particles together into a size the filter can catch.

The pH value comes before everything else. When pH moves out of range, chlorine loses its effectiveness; if you keep adding chlorine and see no result, the problem is usually not the chlorine but the pH. Do not add chemicals without measuring first.

Never mix chemicals together, and store them in their original packaging, closed and in a cool place. When chlorine and acid mix, toxic gas is released. Keep the chemical cabinet away from the electrical panel; chlorine fumes quickly corrode circuit boards and metal parts.

Models that clean only the floor are enough for flat-bottomed pools. Models that climb walls and clean the waterline are needed for pools with stepped floors and deep pools. The cable should be longer than the pool's diagonal.

The capacity of the filter basket and how easy it is to clean determine day-to-day use. Top-opening baskets let you empty the robot without taking it out of the water. Cordless models remove the problem of tangled cables, but charging time and battery life are a separate matter.

A robot does not fully replace manual cleaning. A surface skimmer net, a wall brush and a telescopic pole belong at every pool. The greasy line at the waterline comes off with a brush and a suitable cleaner, not with a robot.

When choosing, look at the IP protection rating, the housing material (stainless steel housings last a long time) and whether the lamp can be changed without draining the water. A fitting that cannot be changed without draining turns into a big job at the first failure.

Pool lighting runs on safety extra-low voltage and is fed through a transformer. This is not a preference but a requirement of electrical safety. The transformer is placed in the plant room, in a dry spot.

On the automation side, the pH and chlorine probes, dosing pumps and control unit are bought as a single package. The probes need periodic calibration; an uncalibrated probe measures wrongly and the system doses wrongly. Buy calibration solution together with the system.

None of these affect the health of the pool.

Places where you should not save: waterproofing, pipe diameter, pump quality and filter size. These four are items that cannot easily be changed once the pool is finished, or that require digging if they are. What you save by going down a pipe size, you pay back every month in electricity.

Then there is the question of brand. Choosing a well-known brand for the pump and filter means you can still find spare parts five years later. A pump with no available parts means a full replacement on the day it breaks down; that is where the difference from the first purchase evens out.

Water quality: disinfectant, pH increaser and reducer, algaecide, clarifier, and a test kit or electronic tester. If dosing will be automatic, add probes, a dosing pump and a control unit.

Cleaning and use: a pool robot or manual vacuum set, surface skimmer net, wall brush, telescopic pole, ladder and pool cover. Put the cover at the top of the list, not the bottom; of all the items, it pays back fastest on heating and water loss.