How to Vacuum Pool to Waste – Cleaning a Dirty Pool

If you have a very dirty pool, particularly when you open it in the spring, it is likely that the only way to clean it properly will be to vacuum pool to waste. This means using the waste setting on a sand filter multiport valve in conjunction with your pool vac.

Vacuuming pool to waste will remove all dirt or algae from the bottom of the pool by sending it via the waste line either to your sewage system or into your yard, instead of going through the pool filter system. This prevents the filter becoming clogged and fine particles going back into the pool.

If you try to vacuum a very dirty pool using the more usual Filter setting then it is likely that the pool filter will become clogged and may even start to allow dust particles and other debris through which will then end up back in the pool.

The other reason you may need to vacuum to waste might be if you have a heavy infestation of algae. Algae particles can be too small to be caught by the sand or other filter medium so if vacuumed on the filter setting they will probably just end up being redeposited back into the pool. So in this situation vacuuming to waste is the best solution to remove the algae from the pool after it has been killed using shock treatment..

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Step by step guide – How to vacuum pool to waste

Step 1 – Top up the pool

How to vacuum a pool to waste

When you vacuum a pool to waste the water does not return to the pool but instead is expelled either down a drain or into your yard. Because of this the level of water in the pool will go down as you vacuum – at quite a fast rate too.

So to compensate for that it is a good idea to run a garden hose into the pool for a while before you start to vacuum to raise the level of the water. It is also prudent to leave the hose running while you vacuum too.

Step 2 – Run out the backwash hose

vacuum to waste - backwash hose

If your pool system does not expel the water down a drain then it will run out into your yard somewhere via the waste line. You can buy roll up backwash hoses quite cheaply on Amazon.

I have actually adapted an old vacuum hose to use s a backwash hose to distribute the water around my garden (see photo above).

Step 3 – Connect the vacuum up

how to vacuum a pool to waste - connect vacuum

Connect the pool vacuum hose to the vacuum head (already attached to a pole of course) and lower it into the pool. Expel the air from the vacuum hose and connect to the skimmer port. See my post How to remove air from a pool vacuum hose to find out how to do this.

Step 4 – Multiport valve to waste

multiport valve set to waste

With the pool pump off, move the multiport valve selector to the Waste position. If you have a valve that shuts off water to the waste pipe (I have one on my pool set-up) then make sure this is open.

Now switch the pool pump back on.

Step 5 – Begin vacuuming

pool vacuum to waste

Begin vacuuming the pool as normal however the water level will start to go down rapidly so you really need to work quickly when vacuuming to waste.

vacuuming pool to waste

I would recommend not trying to get the bottom of the pool completely clean in this first clean.

If you spend too much time trying to remove all traces of dirt then the water level will drop below the level of the bottom of the skimmer and air will start to get into the system. You will then have to turn off the pool pump and let the water level go up again from the hose before you can start again.

vacuuming a pool to waste

The above photo was taken half way through vacuuming and you can hopefully see the brighter area above the water line. This is how much the water level had dropped, which must have been at least 2 inches, and in no more than 5 minutes.

vacuum to waste sand filter
Almost finished and what a difference!

Step 6 – Switch off pump

Step 7 – Top up water

Turn on your garden hose, or let it keep running if you have left it doing this while you vacuum to waste like I do. Let it run until it reaches its normal level.

I also have an automatic top-up facility which keeps the pool at the correct lever, and you my have too, but it is much quicker to supplement this with a garden hose too.

Step 8 – Finished

So you just need to remove the vacuum head and vacuum hose from the pool, clear up and put the pump back on after putting the multiport valve back into the Filter position. Don’t forget to roll up your backwash hose too.

Go and make yourself a drink – you have earned it!

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.

Pool care handbook

After Vacuuming pool to waste

I normally check the chemical levels at this stage and add anything necessary to bring the levels to the correct reading.

It is often not possible to remove all all the dirt from the bottom since you need to vacuum so quickly. Also, it is inevitable that while vacuuming quickly to waste that some of the finer dirt particles will have been disturbed and will be floating around the water in suspension.

I therefore let the swimming pool settle down for 24 hours, allowing all the finer dirt to resettle on the bottom, and I then give the pool a thorough vacuum on the filter setting.

Vacuuming to waste video

My video on Youtube

What happens when you vacuum to waste?

When you select waste on the multiport valve, and run the pool pump, the water does not go through the pool filter, nor does it return to the pool via the pool return. Instead it is sent straight out of the pool system, either down the drain into the sewage system or out into the yard somewhere via the waste line and a backwash hose, depending on your particular pool’s set up.

This way the dirt that is picked up by the vacuum does not get trapped in the filter, clogging the filter medium or even returning to the swimming pool, but is ejected from the system completely.

As the water does not go back into the swimming pool the water level will go down as you vacuum, actually at quite an alarming rate, particularly if you have a relatively small pool. It is then that you appreciate just how much water your pool pump actually moves. You will have to top the pool up afterwards.

Do you backwash after you vacuum to waste?

Since the water containing the dirt does not pass through the filter if vacuuming a pool to waste there would normally be no need to backwash afterwards.

If the pressure is high then you may wish to backwash to reduce it and improve suction.

How to vacuum to waste with a cartridge filter?

There sometimes no waste setting on a cartridge filter, at least in a Hayward system, so you cannot filter to waste. However it is possible to fit a Hayward 3 way valve to bypass the filter and if you do that you will then have the facility to vacuum to waste.

Some cartridge filters have a drain plug on the back of the filter housing which you can unscrew. When the pump is run and you vacuum then the water will come out of this hole. Once finished you put the plug back in.

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.


Does the water level drop when vacuuming pool to waste?

When you vacuum using the waste setting the pool water will be expelled, without returning to the pool, so the pool level will drop. You should top the pool up before you begin, leave a hose running and vacuum quickly.

Should you vacuum pool to waste after using flocculant?

Flocculant will normally leave debris on the bottom of your pool so vacuuming to waste will prevent this debris clogging the filter, as would happen if vacuuming on the filter setting.

What is the difference between backwash and waste?

Although both settings send water out of the pool, when you backwash the water flows backwards through the filter first but on waste the water goes directly out of the pool.