A pool clean is mostly the water going round

What the cleaning actually is

Filtration and disinfection are two halves of one job, and the pages say so in different words. Pool water must be regularly circulated and filtered, SA Health's page says, and proper disinfection and filtration of pool water kills harmful microorganisms and removes body fats, oils, soil and other contaminants. The same page gives the consequence of skipping it: if the pool filter does not operate properly, the chemicals added to keep the pool disinfected and clean will not be effective.

Queensland Health's spa page explains why the filter is not just tidying up. "Effective filtration is essential to maintain good water quality", it says, because filtration removes material that can promote the growth of harmful organisms and shield them from the disinfectants. The Better Health Channel describes the mechanism: a pool's water is pumped through a filter that takes out debris and particles, and chlorination is commonly used alongside filtration to inactivate microbes in the water. It adds that the best kept pools use more than one treatment barrier rather than leaning on a single one. Its page names five keys to holding water quality: filtration, chlorination, pH, total alkalinity and calcium hardness.

How long the filter should run

This is the question most people ask, and the official pages shown here do not print a daily number: your state's health page is the one to check. What they do print is a measure of the filter's capacity instead. The filter system should be able to completely filter a volume of water equivalent to the volume of all the water in the pool within six to eight hours, SA Health's page says: that is the filter's throughput, the pool turned over in one working day. Its page then gives the running rule without a number in it: the filtration system should operate continuously when a pool is being used and for at least one hour afterwards.

The Better Health Channel says why no page can give one number for every pool: how long a filter needs to run depends on the size of the pool and the horsepower of its pump, and where that leaves a reader unsure, its advice is to check with the manufacturer or consult a pool maintenance professional. Its page also connects the running time to the chemistry: generally, the longer the filtration cycle, the less chlorine a pool will need, and the more chlorine is used, the shorter the filtration cycle can be. What the water needs also depends on the pump and filter, the temperature and level of the water, how much debris there is and how many people are swimming, so the running time that suits one week may not suit the next.

One limit is worth knowing before any of that is planned. Most pool filters cannot reach all of the water in a pool, the Better Health Channel says, which is why the brushing and vacuuming in the section below matter.

From Better Health Channel.

The backwash, and how often

A sand filter is rinsed backwards to clear what it has caught, and Icon Water's page is the only one here with numbers on it: a sand filter needs backwashing which can use up to 8000 litres of water every year, and backwashing should be carried out once every four to six weeks. The rule for stopping is in the same place: only backwash until the glass goes clear, because backwashing for longer wastes excessive amounts of water. Its page adds the two habits that keep that number down: backwash only when necessary, and keep the pool and filters clean, which reduces how often the backwash is needed at all.

There is a filter that skips the job entirely. A cartridge filter does not require backwashing to be cleaned, so it uses less water, and Icon Water's page suggests one for a new pool or a replacement filter. Where the water goes when it does leave depends on your water utility: the two sewer utilities in the guide to what leaves a pool set opposite rules for it.

From Icon Water.

The hand work the pages name

Under its heading for the regular cleaning every domestic pool needs, SA Health's page lists the work with its reasons built in:

• remove litter and vacuum the bottom of the pool regularly to remove dirt and debris
• scrub the pool walls and surrounding areas regularly to remove debris
• clean the pump lint-pot and filter system regularly, daily when dosing is done by hand
• repair any damaged pool surfaces
• keep pipes, filters and motors in good working order
• service all pool equipment according to the manufacturer's directions
• ensure all electrical equipment is maintained in good condition

Queensland Health's spa page compresses the same idea into one line: "Clean the filter and empty the hair strainer regularly." The Better Health Channel adds the two things a running filter cannot do: brushing and vacuuming a pool regularly, and, when algae has taken hold, vacuuming up what has settled on the pool floor rather than letting the filter run at it. Its list of ways to maintain water quality also puts checking the pump, the skimmer boxes and other pool equipment alongside the brushing, repairing or replacing parts as needed.

From SA Health, Queensland Health on spa pools, Better Health Channel.

The water level, and the leak that is not evaporation

The filter needs a water level it can draw from. Icon Water's page says the water should sit about half way up the opening in the skimmer box for the filter to work properly, and that where an owner wants the level lower than that, a T-piece suction line connected to the skimmer box lets the filter keep working normally.

Below that level, water loss stops being normal. Leaks in a pool can be hard to detect, the same page says, and they can develop in the pool's membrane and its piping; even a small leak can lose 7000 litres of water a year. Its advice is to know the pool's regular water loss first, because a leak should not be mistaken for the loss that splashing and evaporation cause anyway. Where the water drops by the same amount with the filter on and the filter off, the leak is more likely to be in the pool's structure, though a plumbing leak should not be ruled out.

The page is careful about who does the work. For leaking pool pipes its advice is to call in a licensed plumber or a leak detection specialist, and for a leak found before the pump's impeller it says a licensed plumber should be consulted, as a precaution even where the leak looks like one in the pool's structure. The plumber is named rather than the pool trade: the page notes that some plumbers have invested in the equipment for the testing, and others call the leak detection specialists in and then do the work.

From Icon Water.

Where this leaves the cleaning of a pool

A pool's cleaning comes down to the same few acts at different rhythms: the water goes round continuously while the pool is in use and for an hour after, the filter is rinsed when it needs it and never longer than it needs, the surfaces are brushed and vacuumed, the basket in the skimmer box is emptied, and the readings are checked before the water is used. The guide before this one is the check that happens at the same moment as the cleaning: the skimmer box cover that comes off when the basket is emptied, and goes back on locked before anyone is in the water.