Where Does Backwash Pool Water Go? Best Ways to Dump It

When you backwash a pool filter, or when you vacuum a pool to waste, the water that is pumped from the pool does not return to the pool. So where does it go?

When you backwash the pool water exits the pool and in general either goes directly into the sewer system or to somewhere in your yard, such as on a lawn, a flower bed, under trees or wherever you direct it by laying out a backwash hose.

Regulations differ about where you can discharge pool water in different areas of the US and in other countries. You should check with your local authority to find out what you ca do in your particular area.

Where Does Backwash Pool Water Go
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Discharging pool water into a yard

If you have a large garden then this may be a good option, particularly when backwashing or vacuuming to waste. In these situations the volume of water will not be too high so the water will easily percolate through the soil. Some homeowners have very small yards, in fact some I have seen are almost completely filled with their pool, so if that is your situation then you are likely to have to look at the option of having the pool water go into the sewer system (see below).

Ideally you shouldn’t allow backwash pool water that you have just heavily shocked to drain into your garden as this is when it will be at a level that may harm grass, plants and trees. Fortunately, in most instances when you need to backwash or vacuum to waste, the chlorine levels will be at their lowest since you would normally test and shock after doing these.

If you intend pumping the water around your garden, and you don’t already have one, then you will need to but a backwash hose. This will allow you to pump the water into different parts of the garden which will:

  • prevent one area becoming waterlogged
  • ensure that no one area receives too much chlorinated water so protecting the plants

Backwash hoses can by purchased quite cheaply on Amazon.

If you are unsure as to whether it is safe to discharge the pool water around your yard then you can test it using a test kit. Provided the concentration of chlorine is no higher than 0.1 parts per million then it will not be harmful.

Will pool backwash kill grass?

While I wouldn’t recommend flooding a bowling green with water from the pool, most household lawns are made up of hardy grass types such as Ryegrass and Kentucky Bluegrass which will not be harmed by pool water unless you have heavily shocked it before backwashing.

Draining pool water on a lawn should in most places be ok. You can always test before hand by perhaps emptying a bucket of pool water onto an area of the lawn which is out of the way. If it is still fine in a few days then the rest of the lawn should survive without problems too.

Will pool water kill plants?

Different plants will react differently to pool water. Some will tolerate it completely and at the other end of the scale some plants may die. As a very general rule, plants with thick leaves will probably be able to cope with chlorine the best.

Examples of those plants that can tolerate pool water are Oleander, Palms, Honeysuckle and some herbs such as Rosemary. Those that won’t tolerate pool water include some fruit trees and roses.

Should you dechlorinate pool water before draining?

If you will be completely emptying your pool then it may be a good idea to dechlorinate the water in the pool before discharging the entire amount around your property. You can do this by:

  • leaving the pool without adding chlorine for a while, perhaps up to a week, so that the sun breaks down the chlorine in the water
  • Buy some chemicals from your local pool store that are designed to dechlorinate the water. One such chemical is sodium thiosulphate.

If you are just going to backwash or use the waste setting to lower the pool level after rain , or when vacuuming to waste, then the volume of water will be relatively small so dechlorinating should be unnecessary.

Can you backwash into the street or storm drain?

Can you backwash into the street or storm drain

Whether you can direct pool water into the street depends on where you live. It may be permitted in some areas but not in others.

For example, the City of Phoenix state “Do not drain water into the street, alleyway or other city of Phoenix right of way under City Code, Section 31-8 and Section 23-33“. Instead, they state that the water should be discharged onto a lawn or other part of the landscaping unless it will be a substantial amount (such as when emptying the pool) in which case it could go down the home’s sewer clean-out and into the city’s sewer line.

The main reason for not being able to discharge into the street, storm drains, curbs, gutters, channels etc is that, without the water being treated first, they lead to creeks, rivers and lakes. Pool water contains chemicals such as chlorine which could severely impact the ecology of the waterways. Pool water that goes into the sewer system is treated before ending up in rivers, reservoirs etc so it will not impact negatively on the ecology of the waterways.

Check you local area’s regulations to see what they allow as fines for discharging water into the drainage system, where not permitted can carry hefty fines.

Can I drain my pool into the sewer?

In many areas of the US, and in other countries, you can drain your pool into the sewer system although you may find that you are not permitted to to have the backwash/waste pipe permanently connected to the sewer line. In some areas you are allowed to discharge the pool water into the sewer via a backwash hose into a sewer line inlet.

You should check with your local authority to see what the swimming pool drainage regulations are in your area. If you are not permitted to, you will have to discharge the water into your yard somewhere.

The Department of Energy and Environment in Washington, DC has some good advice on draining a pool. How to drain your pool properly.

Once you start to run the water into the sewer you should check inside your house that the water isn’t backing up and causing a flood in your bathroom or kitchen. If it is then obviously you should stop immediately and perhaps get help from a plumber.

Draining above ground pools

If you are wondering where to drain above ground pool water then the rules above also apply. You may need to use a submersible pump if the pump/filter you have does have the ability to backwash or waste, unless you use gravity by siphoning the water using a garden hose.

Pool Maintenance Course

When I first bought my house with a swimming pool I knew nothing about how to clean and maintain it. I was recommended Swim University’s Pool Care Handbook and video course so I bought it and have never regretted it.

It was probably the best money I spent that year as I have saved thousands by doing it myself.

My top 3 pool cleaning tools

These are the pool cleaning tools I have found the most useful since I have had my pool.

Step and corner vacuum brush

This is a really useful tool for getting into the areas that a standard vacuum head simply cannot reach. Aquatix Pro Pool Step & Corner Vacuum Brush

Leaf rake net

If, like me, you get plenty of leaves at the bottom of your pool then a good leaf rake/net is a must. The Stargoods Pool Skimmer Net gets under the leaves easily.

Robotic pool cleaner

These are quite expensive and it was a number of years before I bit the bullet and bought one. I have never regretted it. The Dolphin Nautilus CC Plus is the most recommended pool cleaning robot on all of the pool forums. It not only cleans the bottom of the pool but also the sides and the waterline.