Pool Losing Water: Evaporation vs Leak

Introduction

Is your pool losing water and you don't know if it's normal evaporation or a leak? This is one of the most common questions we receive in Margem Sul, especially during the hot summer months when evaporation is most intense.

Distinguishing between natural evaporation and a real leak is crucial. Evaporation is a normal process that all pools experience. A leak, on the other hand, can cause structural damage, waste water and chemicals, and lead to high costs if not detected and repaired in time.

In this article, we explain how to distinguish between the two phenomena, how to perform the bucket test to confirm if there's a leak, where to look for the most common leaks, and when it's time to call a professional.

Evaporation: What's Normal

How Much Does a Pool Evaporate?

Evaporation depends on several factors:

Typical Evaporation Values

In Margem Sul, typical values are:

Practical example:

• Pool 8m x 4m = 32 m² surface area
• Evaporation of 1 cm = 320 litres of water
• In summer: 1,280-2,240 litres per week

Factors That Increase Evaporation

Environmental:

• Very hot days (>35°C)
• Constant wind
• Low humidity (<40%)
• Large difference between water and air temp.

Pool-related:

• Heated pool
• Waterfalls or fountains running
• Spa jets
• Large surface area
• No cover

Signs of Leak vs. Evaporation

Indicates Normal Evaporation

• Gradual, consistent loss
• Variation with weather conditions
• Loss only when uncovered
• No stains or wet areas around pool
• Dry equipment
• Loss proportional to heat/wind

Indicates Probable Leak

• Constant loss regardless of weather
• Loss continues with cover on
• Need to fill more than 5 cm/week (summer) or 3 cm/week (winter)
• Damp patches around the pool
• Areas of greener grass
• Water in pump room
• Loss of system pressure
• Air bubbles in returns
• Constant need to add chemicals

The Bucket Test

The bucket test is the simplest way to distinguish evaporation from a leak:

How to Do It

Materials:

• Bucket (10-20 litres)
• Tape or marker
• 24-48 hours without using the pool

Procedure:

1. Prepare

• Fill bucket with pool water
• Place bucket on pool step (partially submerged)
• Or suspend on edge with water at same level

1. Mark

• Mark water level inside bucket
• Mark pool water level (on bucket or wall)

1. Wait

• Leave for 24-48 hours
• Don't use the pool
• Keep pump running normally

1. Compare

• Measure drop in bucket (evaporation)
• Measure drop in pool

Interpreting Results

Additional Test: Pump On vs. Off

If the bucket test indicates a leak, do a second test:

1. Test with pump on for 24h
2. Test with pump off for 24h
3. Compare results

Common Leak Locations

In Pool Structure

Liner (vinyl):

• Near lights
• Corners and edges
• Fold areas
• Holes from sharp objects

Concrete/Gunite:

• Structural cracks
• Expansion joints
• Returns and drains

Fibreglass:

• Damaged gelcoat
• Pipe connections

In Circulation System

In Accessories

• Lights: Deteriorated gasket
• Skimmers: Cracks, connection to pool
• Returns: Worn O-rings
• Main drain: Compromised seal

How to Find Leaks

Visual Inspection

In the pool:

1. With goggles, inspect liner/walls
2. Look for bubbles, delamination
3. Check near all accessories
4. Look for visible cracks or damage

Around the pool:

1. Look for constantly wet areas
2. Greener grass in certain spots
3. Ground subsidence or erosion
4. Water stains in pump room

Dye Test

To locate small leaks:

Materials:

• Food colouring or special leak detection dye
• Syringe or dropper

Procedure:

1. Turn off pump (water still)
2. Bring dye close to suspect area
3. If there's a leak, dye will be "sucked in"
4. If not, dye disperses normally

Areas to test:

• Near lights
• Returns
• Skimmers (joint with wall)
• Main drain
• Visible cracks
• Corners and edges

Pressure Test

For buried pipes:

1. Isolate section to test
2. Pressurise with air or water
3. Monitor pressure
4. Pressure drop = leak in that section

This test usually requires professional equipment.

Solutions for Common Leaks

Liner Leaks

Small holes (< 5mm):

• Liner repair kits (glue + patch)
• Can be done underwater
• Temporary to permanent solution

Larger tears:

• Larger patch with special glue
• Consider replacement if badly damaged

Near accessories:

• Tighten seals
• Replace O-rings
• Reapply silicone/sealant

Concrete Leaks

Fine cracks:

• Epoxy resin injection
• Elastic waterproofing

Structural cracks:

• Structural repair
• Consult engineer if serious

Joints:

• Redo expansion joints
• Apply flexible sealant

Pipe Leaks

Equipment Leaks

Pump:

• Replace mechanical seal
• Check O-rings
• Tighten connections

Filter:

• Replace valve seals
• Check lid O-ring
• Tighten clamps

Typical Repair Costs

When to Call a Professional

You Should Call If:

• Bucket test confirms significant leak
• You can't locate the source
• Leak is in buried piping
• Apparent structural damage
• Loss exceeds 3 cm/day
• Water appearing in unexpected places
• Pump/equipment affected

A Professional Can:

• Use electronic detection equipment
• Perform pressure tests
• Use inspection cameras
• Locate leaks in buried pipes
• Repair structural damage
• Guarantee the work

Leak Prevention

Regular Maintenance

Best Practices

• Don't completely drain (especially liner)
• Keep chemicals balanced (prevents degradation)
• Protect from sharp objects (toys, decorations)
• Proper winterisation (prevents frost damage)
• Control nearby trees (roots can cause damage)

Prevention Investment

• Pool cover: Reduces evaporation 90%+
• Winter cover: Protects from debris and frost
• Leak detection system: Early warning

Frequently Asked Questions

How much water is normal to lose per day?

In summer, 5-10mm per day is normal from evaporation. This equals about 2-3 cm per week in a typical pool. Significantly higher values deserve investigation.

Does the bucket test really work?

Yes, it's surprisingly accurate. The principle is simple: water in the bucket and pool are subject to the same evaporation. If the pool loses more, it's a leak. Do the test for at least 24h for reliable results.

Can I repair a liner leak myself?

Small holes yes, with repair kits available from pool shops. The repair can be done underwater. Large tears or leaks near accessories usually need a professional.

How much does professional leak detection cost?

In Margem Sul, leak detection service typically costs €100-200, depending on complexity. If the leak is found and repaired in the same visit, many companies include detection in the total cost.

Can a small leak wait?

Not recommended. A small leak can:

• Quickly get bigger
• Cause structural damage
• Waste water and chemicals
• Damage ground and adjacent structures
• Significantly increase repair cost

Conclusion

Distinguishing between evaporation and a leak is essential for keeping your pool in good condition. The main points to remember are:

• Know normal values of evaporation for the time of year
• Do the bucket test if you suspect a leak
• Investigate promptly any abnormal loss
• Check common locations for leaks before calling a professional
• Don't ignore small leaks – they tend to get worse

If you need professional help with your pool in Margem Sul, ManutençãoPiscinas is here to help. Contact us for a no-obligation quote.