Think pool care is just skimming leaves and adding chlorine? Think again. The real key to sparkling, healthy water is backwashing; a must-do step that too many pool owners overlook. But it leaves many asking: Where does backwash pool water go and what’s the right way to dispose of it?

In this Hy-Clor guide, we’ll cover what backwash pool water is, where it typically goes, the legal and environmental factors you need to know, and the most effective ways to dispose of it responsibly. Saving you from headaches, fines, and environmental harm.

What Is Backwash Pool Water?

When your pool’s filter becomes clogged with dirt, oils, and other debris, backwashing is the cleaning process that restores it to working order.

Here’s how it works:

  • Sand or DE filters – Water is reversed through the filter to flush out trapped dirt and debris.
  • Cartridge filters – These are usually hosed down manually, but some systems allow a form of backwashing.

The result? A rush of dirty water, known as backwash pool water, that has collected not only dirt and algae but also traces of chlorine and other pool chemicals. That’s why you can’t just let it flow anywhere without a plan.

Where Does Backwash Pool Water Typically Go?

So, when you hit that backwash valve, where does the water go when you backwash a pool? The answer depends on your setup and local regulations.

Into the sewer system

Many modern pools are designed to send backwash water directly into the municipal sewer system. This is often the safest option, as the water will be treated before it re-enters the environment. However, not every property is connected this way, and some councils require specific permits for this kind of disposal.

Onto the lawn or garden

Some pool owners divert backwash water onto lawns or gardens. This can work if the water is diluted and chemicals are neutralised. Grasses and some hardy plants may tolerate it, but sensitive vegetation may not. Always check chlorine levels first to avoid damaging your landscape.

Stormwater drains (to avoid)

One place backwash water should never go is the stormwater system. Unlike sewers, storm drains lead straight into rivers, creeks, and the ocean; without treatment. Sending chemically treated water into these drains is harmful to aquatic life and is usually illegal.

Environmental and Legal Considerations for Backwash Water Disposal

Environmental impact 

Backwash water contains:

  • Residual chlorine and pool chemicals
  • Algae and bacteria
  • Organic debris, like leaves and dirt

If released into natural waterways, these can harm fish, contaminate habitats, and disrupt ecosystems. Chlorine, in particular, can strip oxygen from water, while phosphates from pool chemicals may trigger algae blooms that choke local waterways.

Legal requirements

Across Australia, councils and water authorities set rules for how pool water must be discharged. Many prohibit discharge into stormwater drains and may issue fines for non-compliance. 

Some councils specifically require pool water to be connected to the sewer or directed into a soakage trench. Others require you to use a sewer connection or an approved disposal method. That’s why it’s important to know your local regulations before pulling the backwash lever.

Best Practices for Backwash Water Disposal

  • Check local guidelines: Before anything else, consult your local council or water provider. They’ll outline approved methods for disposal.

  • Neutralise chemicals in backwash water: If you plan to divert water to your garden or soakage pit, let chlorine dissipate first. This can be done by holding the water in a temporary containment area for 24–48 hours before release. Alternatively, you can use a chlorine-neutralising product such as sodium thiosulfate to make the water plant-safe faster.

  • Use a backwash recovery system: Some pool owners install recovery systems that filter and recycle backwash water. These systems not only help the environment but can also save you money by reducing water loss. Modern recovery units can recycle most of the water, making them an attractive option for eco-conscious households.

  • Divert water to safe areas: If a sewer connection isn’t possible, directing water to a designated soakage trench or pit is often an acceptable solution. This allows the water to filter naturally through the soil.

How to Minimise Backwash Water Waste

While disposal is important, reducing how often you need to backwash is even better.

  • Maintain your filter regularly to prevent clogging.
  • Use eco-friendly pool equipment that conserves water.
  • Test and balance pool chemistry frequently to reduce unnecessary filter stress.
  • Vacuum debris before it reaches the filter, keeping leaves and dirt out lowers the load on your system.
  • Consider upgrading to a variable-speed pump, which can extend filter life and reduce the need for frequent backwashing.

In drought-prone regions, this can also help comply with water restrictions and lower your utility bills; an added incentive to keep backwashing to a minimum.

FAQs

Usually to the sewer system, a soakage pit, or onto the garden if safe. Never into stormwater drains, as it can pollute waterways.

Sometimes. If chlorine has dissipated, it may be fine for lawns and hardy plants. Test a small area first, as sensitive plants can be damaged.

Typically every 1–2 weeks. Check the pressure gauge, if it’s 8–10 psi above normal, it’s time to backwash.

It can harm the environment, pollute waterways, and breach local regulations, leading to fines.

Yes. Backwashing lowers water levels, so you’ll need to top up the pool to keep circulation and filtration working properly.

Dispose of Backwash Pool Water Safely With Hy-Clor’s Expert Tips and Products

Backwashing your pool is a must for clean, sparkling water; but where that water goes is just as important. By disposing of backwash pool water responsibly, you’re protecting both your pool system and the environment.

At Hy-Clor, we offer a range of products designed to make pool care safer, simpler, and better for the environment. Whether you need expert advice or tools for managing your pool water, Hy-Clor is here to help.

Visit our Learning Centre for more maintenance tips or reach out to our support team for personalised guidance on keeping your pool healthy and compliant.

Shop Hy-Clor’s pool maintenance products here or download our water testing app today to take the guesswork out of pool care!