Inflatable above-ground pool maintenance: chemistry, filter, winter storage

A rigid inflatable pool at 1.5 m depth with 8,000 to 31,000 litres of water demands the same maintenance rigour as any residential pool. The good news: the 330 W sand filter included with every GIGI pool is the same filtration standard used in semi-buried and in-ground pools — it handles these volumes effectively and requires less frequent intervention than a cartridge filter of comparable capacity.

This guide covers the daily and weekly maintenance schedule, water chemistry targets, sand filter operation with backwashing, end-of-season winter storage, and the most common problems with their solutions.

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Maintenance schedule at a glance

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Water chemistry: targets and why they matter

Water chemistry is the foundation of a clean, healthy pool. The sand filter removes physical particles; chemistry manages biological contamination. Maintaining both ensures clear water and avoids problems that are far harder to resolve than to prevent.

Free chlorine: 1–3 mg/L (ppm)

Free chlorine is your primary disinfectant. At 1–3 mg/L, it eliminates bacteria, algae, and pathogens. Below 1 mg/L, the pool is under-disinfected and will turn cloudy or green rapidly in warm weather. Above 5 mg/L, the water irritates eyes and skin.

In southern Europe (Spain, Portugal, southern France), UV degradation consumes chlorine faster than in the north. On a day at 35 °C with direct sunlight on the water surface, unstabilised chlorine can drop from 3 mg/L to near zero in 4 to 6 hours. This is why cyanuric acid (stabiliser) is essential for outdoor pools.

Stabiliser (cyanuric acid): 30–50 mg/L. Cyanuric acid binds to chlorine and protects it from UV degradation. If you use unstabilised chlorine (calcium hypochlorite), add stabiliser separately. Most chlorine tablets (trichlor, dichlor) already contain stabiliser — in this case, check the level every 2–3 weeks and dilute with fresh water if the level exceeds 80 mg/L.

pH: 7.2–7.6

pH is the most important water chemistry parameter to monitor. Within the correct range, chlorine is effective. Below 7.2, the water becomes acidic — aggressive towards the DWF material and irritating to skin and eyes (though chlorine remains very active). Above 7.8, chlorine effectiveness drops sharply (at pH 8.0, only approximately 20% of your chlorine is active) — algae and bacteria proliferate even with an adequate chlorine level.

Test pH at least twice per week. pH naturally drifts upward over time as swimmers, sun cream, and body oils enter the water. Hydrochloric acid or sodium bisulphate lowers pH. Sodium carbonate or soda ash raises it.

Total alkalinity: 80–120 mg/L

Alkalinity is the buffer that stabilises pH. Low alkalinity (below 80 mg/L) makes pH unstable — it swings up and down with every chemical addition. High alkalinity (above 150 mg/L) makes pH difficult to adjust and can cause cloudy water.

Calcium hardness: 200–400 mg/L

Less critical than chlorine or pH, but check monthly. Very low hardness (below 150 mg/L) makes the water "hungry" for calcium — it will seek it from the pool components. Very high hardness causes limescale deposits. Most European tap water falls within the acceptable range.

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The 330 W sand filter: operation and schedule

The 330 W sand filter supplied with GIGI pools is the filtration method used in most residential in-ground and semi-buried pools. It works by passing water through a specially graded sand bed, which retains particles down to 20–30 microns — sufficient to keep a well-maintained pool visibly clear.

Daily operation

Run the sand filter for a minimum of 6 to 8 hours per day during the swimming season. In hot weather (30 °C and above) with heavy use, 8 to 10 hours is more appropriate. Programme the filter on a timer if possible — running it during off-peak hours (night or early morning) is perfectly effective.

The filter valve must be in the FILTER position during normal operation. Check this at the start of each season and after any maintenance intervention.

Never run the filter without water in the pool. The 330 W pump circulates water — running it dry damages the impeller and motor within minutes.

Reading the pressure gauge

The sand filter is fitted with a pressure gauge at the inlet. At the start of each season with a clean sand bed, note the reference pressure — this is your "clean filter" value, typically between 0.3 and 0.8 bar for the 330 W. Write this figure down.

As the sand bed retains debris, pressure increases. When the reading is 0.4 to 0.5 bar above your reference value, it is time to backwash.

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Sand filter backwashing

Backwashing reverses the water flow through the sand bed to expel trapped debris. It is the main filter maintenance task and takes approximately 10 minutes.

When to backwash

• When filter pressure is 0.4 to 0.5 bar above the reference value
• After heavy rain or leaf fall that has loaded the filter
• At the start of each season before filling

Backwash procedure

1. Switch off the filter pump
2. Attach a waste hose to the filter's backwash outlet — this hose must run to a drain, gully, or an area well away from the pool and from children
3. Turn the multiport valve to the BACKWASH position
4. Switch on the pump and run for 2–3 minutes, or until the water in the sight glass (the small transparent window on the valve) runs clear
5. Switch off the pump
6. Turn the multiport valve to RINSE
7. Run the pump for 30–60 seconds on rinse — this re-settles the sand bed before returning to filtration
8. Switch off the pump
9. Return the valve to the FILTER position
10. Switch the pump back on and verify normal operation

Important: Never turn the multiport valve while the pump is running. Always stop the pump first, then turn the valve. Changing position under pressure damages the valve seals.

After each backwash, top up the pool water level if necessary — backwashing discharges 200 to 400 litres of water per cycle depending on the model.

When to replace the filter sand

Filter sand has a working life of approximately 3 to 5 years with normal use. When you observe persistently poor water clarity despite correct chemistry, or when backwashing no longer restores filter performance, the sand bed may be channelled. Replacement involves emptying the filter of its sand, rinsing the tank, and recharging with fresh filter sand (graded silica sand No. 20). Ask your pool supply retailer for the exact grade suited to the 330 W.

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End-of-season winter storage

Correct winter storage is the single most important maintenance step for pool longevity. A GIGI pool stored incorrectly — damp, partially inflated, or in a space that freezes — will show reduced performance from the following season. A correctly stored pool returns to identical performance for 5 to 10 seasons.

Draining

Use the drain valve at the base of the pool or a submersible pump to empty the water. Do not cut corners on draining time — residual water left in the pool during storage causes mould that permanently damages the DWF material. A submersible pump removes the bulk of the water in 1 to 3 hours depending on the model; the last few centimetres can be removed with a wet-and-dry vacuum.

Rinsing and drying

After draining, rinse the inside of the pool with clean water from a garden hose. This removes chemical residues, debris, and limescale deposits. Then:

1. Remove as much residual water as possible
2. Lay the pool out flat in a sunny spot or somewhere with good air circulation
3. Leave to dry for 4 to 6 hours at 25 °C or above — longer in cool or overcast conditions
4. Check all surfaces by pressing your palm against them — if they feel damp or cool, more drying time is needed

The pool must be completely dry before folding. Any moisture retained in the folds will develop mould within days of storage.

Deflating and folding

1. Open all inflation valves to allow the pool to deflate
2. Use the pump in deflation mode to speed up the process
3. Once fully deflated, fold the pool flat following the original factory fold lines — this minimises stress on the DWF material fold points
4. Roll the pool from one side to the other, keeping the fold lines aligned

Tip: Lightly dust the folded pool with talcum powder before rolling — this prevents surfaces from sticking together during storage and extends the life of the material.

Storage conditions

• Folded and deflated inside a sturdy bag or rigid container
• Location: cool, dry, away from direct light — a garage shelf, cellar, or indoor utility room are ideal
• Temperature: above -10 °C — do not allow the stored pool to freeze
• Do not store under heavy objects that could compress the DWF material

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Troubleshooting common problems

Cloudy water

Symptom: Water is hazy, not clear. Cause: Low chlorine, high pH, or insufficient filtration run time. Solution:

1. Test the chemistry. If free chlorine is below 1 mg/L, shock the pool (raise chlorine to 5–10 mg/L)
2. Adjust pH to 7.2–7.6 (a lower pH makes the shock more effective)
3. Run the sand filter continuously for 24 hours
4. Retest and adjust. If the water remains cloudy after 48 hours of treatment, add a flocculant (coagulating polymer) and run the filter on continuous cycle

Green water (algae)

Symptom: Water turns green, usually rapidly following a period of low chlorine. Cause: Algae bloom due to insufficient disinfection. Solution:

1. Test and first adjust pH to 7.2–7.4
2. Superchlorinate (shock) the pool: raise free chlorine to 10–15 mg/L with a calcium hypochlorite shock treatment. For a 14,000-litre pool (4 m round), this requires approximately 700 g to 900 g of cal-hypo at 65–70% active chlorine.
3. Run the filter continuously
4. Brush all walls and the floor to break up algae colonies and expose them to the chlorine
5. Test every 8 hours — when chlorine returns to 1–3 mg/L and the water is clear, the algae crisis is resolved
6. Backwash the filter immediately after treatment to remove dead algae from the sand bed

Loss of inflation pressure

Symptom: Walls feel noticeably softer after a few days. Cause: Slow air leak from a valve, seam, or small puncture. Solution:

1. Inflate to 0.7–0.9 bar, close all valves, note the pressure
2. Recheck after 24 hours. A slight loss (0.03–0.07 bar) due to temperature change is normal. A loss of 0.15 bar or more indicates a genuine leak.
3. Mix soapy water and apply it first to all valves — look for bubbles
4. If valves are airtight, fully inflate and systematically apply soapy water to the entire outer surface of the pool
5. When you find the leak: dry the area, apply the repair patch from the included kit (follow adhesive instructions), allow to cure for 24 hours before re-inflating

Sand in the filter return water

Symptom: Fine sand grains in the pool water, coming from the filter return. Cause: Damaged lateral (the star-shaped element at the base of the sand bed inside the filter tank). Solution: Switch off the filter. Inspect the lateral inside the filter body — it may be cracked, allowing sand to pass through. Replacement laterals are standard parts available from pool supply retailers. This repair requires opening the filter and partially removing the sand.

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Frequently asked questions

How long should I run the filter on a GIGI pool? Run the 330 W sand filter for a minimum of 6 to 8 hours per day during the swimming season. In hot weather (30 °C and above) with heavy use, 8 to 10 hours is appropriate. Running the filter during off-peak hours (overnight) is perfectly effective. Never run the filter without water in the pool.

What chemicals do I need for a GIGI above-ground inflatable pool? Standard pool chemicals: chlorine (tablets or granules, target 1–3 mg/L free chlorine), pH adjuster (target 7.2–7.6), alkalinity adjusters (target 80–120 mg/L), cyanuric acid stabiliser if using unstabilised chlorine outdoors (target 30–50 mg/L), and preventive algicide. All are compatible with DWF material. Always dose by volume — a GIGI 4 m round pool at 1.5 m contains approximately 14,000 litres.

How do I backwash the GIGI sand filter? Switch off the pump. Attach a waste hose to the backwash outlet. Turn the multiport valve to BACKWASH. Run the pump for 2–3 minutes until the water in the sight glass runs clear. Switch off the pump. Move to RINSE for 30–60 seconds. Switch off the pump. Return to FILTER. Switch the pump back on. Never operate the multiport valve with the pump running — always stop the pump first.

How do I store a GIGI pool for winter? Drain completely, rinse with clean water, and allow to dry thoroughly (minimum 4–6 hours in warm weather). Every surface must be dry before folding. Deflate completely, fold along the original fold lines, dust lightly with talcum powder, and store in a sturdy bag in a dry location above -10 °C. Never store damp or in freezing conditions.

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Related articles

• How to install a rigid inflatable pool: complete guide
• How to choose the size of your GIGI pool
• Inflatable above-ground pool vs framed pool: which to choose?

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Questions about maintaining your GIGI pool? Contact us at contact@gigifrance.fr or on +33 7 80 80 67 64 — we respond within 1 working day. View the FAQ for quick answers. View GIGI pools.