Introduction
Verdizela has one characteristic that completely defines how its pools are maintained, and it has nothing to do with size or finish: many of these houses are not lived in every day.
They are second homes, weekend houses, houses used intensively in August and empty in November. And a pool at an empty house behaves completely differently from a pool at an occupied one — not because treatment is missing, but because the daily five-minute gesture that prevents almost every problem is missing.
This article is about the intermittently used pool: what degrades while nobody is there, what to automate, and how to arrive on Friday without finding the pool green. It applies to Verdizela, Aroeira, Charneca de Caparica and any weekend house with a pool on the South Bank.
The Cycle Everybody Knows
The pattern repeats so reliably that it can be described with times.
Friday, 7pm. You arrive at the house. The water is slightly cloudy with pine needles on the floor.
Saturday morning. You vacuum, brush, add product, run the pump for more hours.
Saturday afternoon. The water has improved but is not right. You shock it.
Sunday. The pool is finally usable. You leave in the late afternoon.
Two weeks later, Friday, 7pm. The whole thing repeats.
What happened is simple: you spent the weekend recovering the pool instead of using it. And the problem is neither the product nor the equipment: it is that thirteen of the fourteen days had nobody passing a net over it.
What Degrades While Nobody Is There
Four things, and each has a different solution.
1. Organic matter accumulates and decomposes
Pine needles, leaves and insects fall every day. Removed the same day, they do practically nothing. Left for two weeks they decompose: releasing tannins, which lower the pH and darken the water, and phosphates, which feed algae.
In a pine area like Verdizela this is the dominant factor. We covered the mechanism in detail in Aroeira Pools: Caring for Them Among the Pines.
2. The disinfectant runs out
Chlorine degrades with sun and heat, even with no bathers. A dose applied on a Sunday can be practically exhausted by the following Wednesday, and from then on the pool has no protection for days.
3. The pH drifts
With no correction, the pH moves out of range. In a pine area it falls, because of the tannins. When it falls far, whatever disinfectant remains loses effectiveness and the water becomes aggressive to the equipment.
4. Nothing warns you when something fails
A pump that trips the RCD on a Tuesday stays off until Friday. A leak that starts on a Monday drains enough for the skimmer to draw air and the pump to run dry. In an occupied house somebody notices within hours; in an empty house nobody notices for days.
The Solution in Three Layers
It is not about choosing one: it is adding all three, in ascending order of cost.
Layer 1: Automate the dosing
The highest-impact intervention. An automatic dosing system measures and corrects continuously, holding the disinfectant and pH steady on the days nobody is there.
On an intermittently used pool this eliminates points 2 and 3 above at a stroke. It is the difference between arriving to a pool with correct chlorine and arriving to a pool that has had no protection for four days. See Automatic Chlorine Dosing Systems.
Layer 2: Cover it and programme the filtration
A cover. At an empty house, the cover is what keeps organic matter out. A pool covered through two weeks of absence takes in a fraction of what an uncovered pool does. It solves point 1 without requiring anyone to be present.
Filtration programmed for the absence. Do not switch the pump off when you leave. Programme it for the hours the volume requires — the number comes from turnover time — and keep it running. A variable-speed pump at low speed over more hours consumes little and keeps the water moving.
Layer 3: Somebody who comes by
This is the layer that solves point 4, and no automation replaces it. An automatic system doses, but it does not net needles off the floor, does not clean the skimmer basket, does not replace a seal and does not top up the water level.
At an intermittently used house, a scheduled visit — weekly in season, fortnightly outside it — is what turns the recovery weekend into a weekend of use. And it is also what finds the stopped pump on Tuesday rather than Friday.
💡 Dica Profissional
If you can only do one thing, cover the pool when you leave. In a pine area, a cover prevents more problems than any product — and it is the only measure that acts during the thirteen days you are not there.
The Extended-Absence Regime
For long periods with no use — October to April, typically:
| Item | What to do |
|---|---|
| Water level | Fill to normal before leaving. Do not lower it |
| Filtration | Keep it, on a reduced regime. Never switch it off entirely |
| Disinfectant | A steady level, with automatic dosing or a periodic visit |
| Cover | Installed and pulled taut, with no pockets of water on top |
| pH and alkalinity | Corrected before the absence begins |
| Equipment | Check before leaving. A fault found in November costs half what the same fault costs found in April |
The classic error: switching everything off in October and coming back in April. A pool with standing water and no disinfectant for five months is not a winterised pool — it is an abandoned one, and the April recovery costs far more than the reduced maintenance would have. See Pool Winterisation: Complete Guide.
And If the House Is Let?
Many houses in this area alternate between own use and letting — seasonally, or as a holiday rental. In that case the regime changes in kind: it is no longer an intermittently used pool, it is a pool in intensive use for periods.
The practical difference is large: bather load rises, the reliability requirement rises (a paying guest does not accept "I am recovering the pool"), and keeping a written record of what was done starts to make sense. We covered what changes in Pool Maintenance for Holiday Rentals.
Common Mistakes
Switching the pump off when you leave. Standing water in an uncovered pool for two weeks is the shortest route to a green pool.
Shocking the pool on every arrival. You are treating the symptom repeatedly. Treat the cause: continuous dosing and a cover.
Not covering in a pine area. It is the measure that acts on the days you are not there.
Lowering the water level when you leave. A pool at a low level has the skimmer drawing air when the pump starts.
A cover with pockets of water on top. Weight, organic matter and an insect breeding site.
Frequently Asked Questions
Should I switch the pump off when I am not at the house?
No. A pool with standing water and a disinfectant running out degrades within days. Keep filtration programmed for the hours the volume requires — reduced out of season, but never zero.
Why is the pool always cloudy when I arrive?
Two weeks of organic matter decomposing, with the disinfectant exhausted halfway through. Both causes are solved with a cover and automatic dosing, which act while you are away.
Is automatic dosing worth installing at a weekend house?
It is probably the best-returning investment on an intermittently used pool. It holds the disinfectant and pH steady on exactly the days nobody can correct anything.
Can I just add more product before I leave?
It helps little. An initial overdose degrades quickly with sun and heat, and in the last days of the period the pool is unprotected anyway. What works is continuous dosing, not one large dose.
What do I do if I will not visit for six months?
The extended-absence regime: full level, reduced but active filtration, steady disinfectant, cover installed, and a periodic check. Switching everything off is the decision that costs most in April.
The pool goes green from one weekend to the next. Is that normal?
It is not normal, it is predictable — in a pine area, with the disinfectant exhausted and phosphates from decomposing needles, algae have every condition they need. Measure phosphates and treat the cause instead of shocking on every arrival.
Conclusion
On an intermittently used pool, the problem is not the two days you are there: it is the twelve you are not.
Key points to remember:
- What degrades the pool is the missing daily gesture, not a lack of product.
- Covering it when you leave is the measure that acts on the days you are absent.
- Automatic dosing holds the disinfectant and pH steady with nobody present.
- Never switch the pump off when you leave, and never lower the water level.
- No automation replaces somebody coming by: the net, the basket and the level need hands.
If you have a weekend house in Verdizela, Aroeira or Charneca and spend half your visits recovering the pool, the on-site technical diagnosis assesses what can be automated on your installation and how often the pool needs a visit. It costs €45, deductible from your first month under contract.
