Is your pool leaking or just evaporating? How to tell

The quickest way to tell a pool leak from evaporation is a 24-hour bucket test: if the pool drops further than water in a bucket sitting on the step, the pool is probably leaking. This guide walks Sunshine Coast owners through that test, the pump-on and pump-off follow-up, the leak spots manufacturers name and where your own checks should stop.

Quick answer: leak or evaporation?

A pool is probably leaking when its water level falls faster than a bucket of pool water sitting beside it over the same 24 hours. Pool equipment maker AstralPool says pools normally lose some water to evaporation and splashing, so a falling level alone proves nothing. The bucket test helps separate the two. Set a 15 to 20 litre bucket on the second step, fill it to match the pool level, mark both levels, turn off the equipment and any automatic top-up, then compare after a day. According to AstralPool, if both levels drop evenly the loss is evaporation, and if the pool level ends up lower than the bucket you likely have a leak. Run the test again with the pump on to see whether circulation makes the loss worse, which AstralPool says points to a leak in the filtration system or plumbing.

How much water loss is normal on the Sunshine Coast?

Normal Sunshine Coast pool water loss tracks the weather, and local evaporation records point to a few millimetres a day in summer and roughly half that in winter. We could not find a published, measured pool loss rate for the region, but Bureau of Meteorology records give useful context. At the Nambour DPI station, mean daily pan evaporation was 5.2 mm in January, 5.3 mm in December and 2.3 mm in June, averaging 3.9 mm a day across the year (records from 1965 to 2007). Treat those figures as a guide only: they come from an open evaporation pan, not a pool, and the Bureau notes that evaporation depends on cloudiness, air temperature and wind speed.

Several local factors change what you see at the waterline:

• Wet-season rain. The Bureau’s Sunshine Coast Airport records show February as the wettest month, with a mean of 214.8 mm and about 12 days with 1 mm or more of rain. Rain topping up the pool can hide a slow leak.
• Heating. Keep a heat pump or solar system set the same way on both bucket-test days, so the readings are comparable, and note which days heating ran when you log the level.
• Covers and water level. The Australian Government’s Your Home guide says pool covers significantly reduce evaporative losses, and an overfilled pool loses more water through splashing. Our guide to whether a pool cover is worth it covers the trade-offs.

Step-by-step bucket test

The bucket test compares a bucket of pool water against the pool itself for 24 hours, and it follows the method published by AstralPool and Baracuda, both Fluidra brands in Australia.

1. Place an empty 15 to 20 litre plastic bucket on the second step so it sits in the pool water.
2. Fill the bucket with pool water until the level inside matches the pool level outside.
3. Mark the water level inside the bucket with a permanent marker or tape, and mark the pool level on the skimmer or tile line.
4. Turn off the pump and any automatic top-up valve, as Baracuda advises, so nothing adds or removes water.
5. Wait 24 hours, then measure both drops in millimetres.
6. Repeat for another 24 hours with the pump running.

Do not run the test when rain is forecast, because rain can overflow the bucket or wash runoff into the pool. Also avoid swimmers and putting a cover on or taking it off between readings, because these change the pool level but not the bucket. To turn a reading into litres, multiply the pool’s surface area in square metres by the extra drop in millimetres: a 32 square metre pool that drops 5 mm more than the bucket has lost about 160 litres more than evaporation explains.

Pump-on vs pump-off test: what the result tells you

Comparing a pump-off day with a pump-on day shows whether the leak depends on water circulating. AstralPool says that if loss is greater with water circulating under pressure, the leak is likely somewhere in the filtration system or plumbing. The other two patterns are less clear-cut, so treat them as a guide to what a repairer should test next.

Signs of a leak around the pool and equipment

The clearest signs of a pool leak, apart from a failed bucket test, are water where it should not be and equipment behaving differently. AstralPool recommends inspecting the whole filtration system first, including the pump, filter, heater, chlorinator, O-rings and connections, because these leaks are easy to locate and reach. Look for:

• Wet ground or walls around the pool. AstralPool suggests checking the ground and walls around the pool to narrow the search before using dye.
• Drips under the pump. AstralPool says a leaking pump can be caused by a pressure-side leak, and suggests checking the impeller housing O-ring and shaft seal for wear.
• Air bubbles in the pump basket. According to AstralPool, a pump sucking air can point to a loose lid or worn plumbing, valves, O-rings or gaskets.
• Cracks in tiles, render or coping, or gaps where the skimmer meets the pool wall.

Equipment symptoms such as noise or poor flow overlap with pump faults, so read Pool Pump Not Working? What to Check First and When to Call a Pro alongside this guide.

Where pools most commonly leak: symptom-to-source decision table

Baracuda names a separation between the plastic skimmer and a concrete pool as the most common leak, and AstralPool adds pool lights and liners to the usual list. Baracuda also says that if the water level stops falling at the bottom of the skimmer opening, the leak is likely in the filtration system. Do not let the pool keep draining to find that point: watch the level for a day or two at most, top up before it falls below the skimmer, and call a repairer straight away for a fibreglass pool or fast loss. Use the table to match what you see with the likely source.

Dye test for skimmers, returns, light niches and cracks

A dye test confirms the exact spot where water is escaping by showing dye being drawn into a gap. AstralPool’s method is to turn off the filtration system, go to the suspected area and release dye close to the wall and surface without disturbing the water; if the leak is nearby, the dye moves towards it. Baracuda lists leak finder dye, or red or dark food colouring. Hold still, release a small amount at a time, and mark any spot that draws dye with waterproof tape.

Start with the places the bucket and pump tests point to: the skimmer throat and the joint where it meets the wall, each return fitting, cracks along the tile line, then the light niche. At a light, check from the edge without touching the fitting, and do not unscrew or open it. Queensland’s Electrical Safety Office advises checking underwater lights regularly for glass cracks or defective seals, and says a licensed electrician must install and maintain pool wiring and electrical equipment. A deep spot means getting in with goggles, so only test the floor if you swim confidently and someone is watching.

Concrete vs fibreglass vs vinyl: how leaks show up differently

How a leak shows up depends on what the pool is built from, because each shell type has different weak points. The table compares where to look, not which pool is better.

What you can safely check yourself vs when to call a pool repairer

Owners can safely measure, observe and dye test, but draining the pool, opening equipment and anything electrical belongs with a professional. Queensland’s Electrical Safety Office says a licensed electrician must install and maintain pool wiring and electrical equipment, and that DIY electrical work is unlicensed work, which is illegal. Waterco, which makes hydrostatic valves for fibreglass pools, says those valves exist to stop a shell lifting out of the ground when the water level is low or there is excess water under the pool, so lowering or emptying a fibreglass pool is not a home experiment.

If the bucket test shows a leak you cannot place, book a pool repair on the Sunshine Coast, or pool pump repairs if the loss is at the equipment.

What a professional leak detection and repair visit involves

A professional leak visit starts with your evidence and moves on to tests an owner cannot do. Bring your bucket readings, the date of any rain and photos of wet patches or cracks, since this narrows the search. Baracuda says a professional can pressure test the lines for possible cracks when underground piping is suspected, and both Baracuda and AstralPool note that not all leaks can be found with DIY methods, so a pool that still loses water after a skimmer patch deserves a proper inspection.

What a leak job involves, and what it costs, depends on how many tests are needed, whether the leak is at accessible equipment or buried pipework, whether the pool must be partly lowered under supervision, and whether the repair is a seal, a fitting or the shell itself. Equipment leaks also raise the repair or replace question: AstralPool says a worn impeller housing O-ring or shaft seal can be replaced, while an old pump with several faults may be worth comparing against a variable speed pump, and filter housings are covered in our sand vs cartridge filter guide. Billabong Pool Service has pool shops in Noosa, Maroochydore and Caloundra, or you can get in touch to arrange a repair.