Empty a green pool: when treatment has failed

You have added the treatment, left the pool alone and come back to water that still looks like green soup. That does not mean you should empty a green pool immediately. The useful decision is whether the algae is being removed by a working circulation system, or whether you are repeatedly dosing water that your equipment cannot clean.

The listing details below come from amazon.co.uk cards in the pool-care comparisons, including the Kleen Pool 1 litre algaecide at about £17.95 with 4.6 from 585 United Kingdom reviews. This is not a lab test. A purchase through our links can earn a commission at no extra cost to you.

In short

Do not drain a green pool just because it still looks unchanged on the first afternoon. Brush it, keep the pump and filter running, and check whether dead algae is settling. Emptying becomes reasonable when correct treatment and working circulation have made no useful progress, or when you have no practical way to filter the water at all.

Dead algae is not a failed dose

A green floor and green water are different problems. If material has settled after treatment, the bottle may have affected the algae even though the pool does not yet look ready to use. That residue still has to leave the pool: chemical treatment does not pick it up, carry it to the filter or sweep it from corners.

Look at where the colour is. Water that is becoming less cloudy while a layer collects on the base is not behaving like water that remains uniformly green. Brush or sweep the deposit using the equipment intended for your pool, then let circulation move the remaining suspended material towards the filter. PWTAG's published response to typical algae problems is to brush affected surfaces and maintain circulation; dumping the water is not its printed first action.

A whole bottle can appear to have done nothing because the dose was wrong for the volume, the pump was off, or the floor was never brushed. Appearance alone cannot tell you which. Do not turn settled algae into a reason for uncontrolled overdosing. The label sets the dose. If the card you bought from does not print the millilitre amount, use the instructions on the bottle and your pool's known water volume rather than estimating from colour.

Wait for the filter before you condemn the bottle

There is no supported UK day-count after which every green garden pool must be drained. The amount of growth, the water volume, the product label, whether the pool was brushed and whether the filter has run all change what you see. The first hour tells you very little, and the first afternoon is too soon to conclude that the water is beyond recovery.

UK review patterns show both sides. Some Clearwater buyers described pools clearing on the second day after the situation first looked like a failure. Others still had green water after a week, including accounts of a double dose or a whole bottle making no useful difference. Those reviews do not create a universal deadline. Several days with visible movement is different from a full week of correct treatment, brushing and uninterrupted working circulation with none.

Kleen Pool reviews tell a similar story. Some winter pools opened clear without being dumped, while a minority reported that a whole bottle did nothing or made the water look greener. One reported 10,000-litre pool cleared after chlorine shock the day before and with the pump left running. That is evidence for a combined process, not proof that one liquid independently rescued the water.

If you are choosing an algaecide, the algae-killer comparison explains what the UK listings do and do not state. The Kleen Pool 1 litre listing says it treats 28,000 litres and lasts six months, but the six-month period remains a title claim. Its UK reviews support use in circulating or winter-closed swimming pools; they do not support treating it as a substitute for filtration.

Checks before you decide to drain

Before losing the water and the treatment already in it, separate a slow clean-up from a system that cannot complete the job. The aim is not to keep spending indefinitely.

1. Confirm what you dosed. Read the bottle label again and compare the instruction with the pool's water volume. Do not add a second dose merely because the first did not produce an instant colour change, and do not assume that one whole bottle is automatically one treatment.
2. Check that circulation is real. A humming pump is not enough if water is not moving through the filter. Observe the return flow and follow the equipment instructions. If you are considering an upgrade, compare a sand filter with the circulation you already have, rather than inventing a flow-rate requirement.
3. Brush the surfaces. Growth can cling to the floor and walls. Brushing breaks up those areas and gives the circulation system a chance to carry the material away.
4. Inspect the floor after circulation. Settled residue needs physical removal. Its presence is not, by itself, proof that the dose failed.
5. Judge the trend, not one photograph. Note whether the water is becoming less opaque, whether the green is moving to the floor and whether the filter is collecting material. No change after a properly managed week is more meaningful than no change after lunch.

For a frame pool, the above-ground algae guide sets this decision in the context of a temporary garden vessel. It is useful when the temptation is to choose between another bottle and a complete refill without first asking what the pump has actually done.

When emptying a green pool is reasonable

Emptying becomes a rational option when recovery is not merely slow but structurally incomplete. The clearest example is a sizeable green pool with no pump or no usable filter. A chemical can be distributed imperfectly by hand, but it cannot collect suspended algae or remove the layer that drops to the base. A bottle cannot replace equipment you do not have.

The second case is persistent failure despite doing the basics correctly. If you followed the label, brushed the pool, ran a functioning circulation system and still see no useful improvement after about a week, further product is a poor bet. That does not prove every treatment has failed chemically. It means the observable process has stalled.

The third case is practical scale. A small, refillable vessel with no filtration may cost less in water and effort to reset than to keep treating. A large frame pool is different: dumping it discards a substantial volume and every chemical already added, then leaves you to refill and begin water care again. Size changes the decision even when the colour looks identical.

Do not use emptying as a way to avoid diagnosing broken circulation. If you refill a pool but keep the same non-working pump, you have reset the appearance without correcting the weakness that allowed the problem to persist. Do not keep adding algaecide merely to protect the cost of water already in the pool. For a public or commercially operated pool, follow the procedures that apply to that facility. This article addresses domestic vessels, review patterns and general circulation guidance.

A paddling pool is a smaller decision

A paddling pool may reach the empty-and-refill point sooner because its water volume is small and many models have no pump or filter. Even if a treatment affects the algae, there may be no system to remove what remains. The reduced refill burden can make a reset proportionate where it would be wasteful for a large above-ground pool.

Smaller does not mean dose casually. The Clearwater 1 litre listing names paddling pools among its intended vessels, but it does not print a millilitre dose or treatment volume on the Amazon card. It directs the buyer to the bottle, with the amount depending on water volume. A product that also names larger above-ground pools cannot be poured into a paddling pool by guesswork.

Check the label and decide whether the vessel can realistically circulate or filter the water. If it cannot, and the water is heavily green rather than a small patch you can clean, emptying may be the more controlled choice. Discard the water appropriately and clean the vessel before refilling. One review reported Clearwater working in a rainwater-filled Bestway pool. Treat that as one buyer's experience. The useful facts remain the labelled dose, the vessel volume and whether you can circulate and remove material.

Where the old water goes

Deciding to drain is not the same as having permission to send treated water anywhere convenient. No single legal UK instruction was established that fits every home, sewer arrangement and local wastewater authority. Do not turn that gap into a direction to discharge into a road drain, street or neighbouring land.

Check the treatment label first, because it may contain handling or disposal instructions for what is already in the pool. Then check the local wastewater rules for your address and planned outlet. If those sources do not make the permitted route clear, ask the relevant local provider rather than assuming that diluted or green water is harmless.

Plan the discharge before opening a valve. A controlled route matters for a paddling pool as well as a frame pool, even though the quantities differ. The water also contains the chemicals you have already added, so old water does not mean untreated rainwater. Once the pool is empty, remove the residue and inspect the equipment before refilling. A reset is useful only if you correct the missing circulation, dirty surfaces or failed filtering. Otherwise, fresh water can put you back at the beginning of the same sequence.