Keeping the Water Clear

Everything you have read about pool chemistry was almost certainly written for a 40,000-litre in-ground pool. An above-ground pool holds a third of that or less, and that changes the rules completely. Chemistry moves faster, mistakes show within hours rather than days, and the sun does far more damage relative to the volume. This guide is written specifically for small pools in a Portuguese climate.

Why Small Pools Behave Differently

In a 14,000-litre pool, a dose that would be a rounding error in a large pool is a significant change. That cuts both ways: problems appear quickly, but they also correct quickly if you catch them. The bigger issue is heat and light. A shallow pool in full Portuguese sun can reach 30°C by mid-August, which accelerates both chlorine loss and algae growth, while UV strips unstabilised chlorine within hours. Most above-ground pools that go green do so between the third and fifth week of a heatwave, and almost always for the same three reasons.

The Weekly Routine

Twenty minutes a week, plus two minutes a day with the net. That is genuinely all it takes.

1. 1
   Test the water twice a week in high season, and after any heavy use or storm. Chlorine between 1 and 3 ppm, pH between 7.2 and 7.6.
2. 2
   Correct pH before anything else. Chlorine barely works above pH 7.8, so dosing more chlorine into high-pH water simply wastes it.
3. 3
   Run the filter long enough to turn the whole volume over at least once a day — in a Portuguese July that usually means eight to twelve hours, split across the hottest part of the day.
4. 4
   Rinse the filter cartridge with a hose every week, and replace it entirely every three to four weeks. A cartridge that looks clean when wet is usually already restricting flow.
5. 5
   Skim the surface daily. Two minutes with a net removes the organic material that would otherwise consume your chlorine overnight.
6. 6
   Brush the walls and floor once a week, especially the corners and the area under the return jet where circulation is weakest.
7. 7
   Keep the cover on whenever the pool is not in use. It reduces evaporation, keeps debris out and dramatically slows chlorine loss to UV.
8. 8
   Watch the stabiliser (cyanuric acid) level if you use stabilised tablets. In a small pool it accumulates fast; above roughly 50 ppm the chlorine becomes progressively less effective and the only fix is to replace some of the water.
9. 9
   Top up the water level to mid-skimmer. A pool that drops below the intake will run the pump dry and destroy it in minutes.
10. 10
    Shock the pool after heavy use, a party, or a period above 30°C — small pools recover quickly, but only if you act before the water turns.
11. 11
    Check the pump for airlocks and the hoses for weeping at the clamps. Above-ground fittings loosen with thermal cycling far more than fixed plumbing does.
12. 12
    Once a month, look at the frame: legs still vertical, no water pooling under one side, no rust bloom at the joints. Water care and structural care are the same job on these pools.

Through a Portuguese Season

From May into June, a light routine is enough — the water is cool and demand is low. July and August are where above-ground pools are won or lost: water temperatures climb, UV is at maximum, and a pool left for a fortnight while you are away will very often be green when you return. September is easier again, and it is also the point at which most owners stop testing too early, which is why so many pools are put away dirty. If you are away for a stretch of the summer, or you would simply rather not think about it, our team covers above-ground pools on the same maintenance visits as any other pool — the chemistry is smaller, but it is the same work.

If you would rather not handle this yourself, these are the services that cover what you just read.

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