How to Vacuum a 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 to waste. This means using the waste setting on a sand filter multiport valve in conjunction with your pool vac.

Vacuuming to waste will remove all dirt and algae from the bottom of the pool by sending it via the waste outlet pipe either to your sewage system or into your yard, instead of going through the pool filter system.

If you try to vacuum a very dirty pool using the more usual Filter setting then it is likely that the 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.

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Step by step guide – vacuum a 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 hose into the pool for a while before you start to vacuum to raise the water level. It is also prudent to leave the hose running while you vacuum too.

Step 2 – Run out the waste 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. You can buy roll up backwash hoses quite cheaply on Amazon.

I have actually adapted an old vacuum hose to use 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 vacuum hose to the vacuum head (already attached to a pole of course) and lower it into the pool. Expel the air from the hose and connect to the skimmer port. See my post How to remove air from a 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 – Start to vacuum

pool vacuum to waste

Start to vacuum 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.

how do you clean a dirty pool
vacuum to waste sand filter
Almost finished and what a difference!

Step 6 – Switch off pump

Step 7 – Top up water

Turn on your 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 and hose from the pool, clear up and put the pump back on after putting the multiport valve back into the Filter position.

After Vacuuming 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 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 put the multiport valve on the waste setting, and run the pool pump, the water does not go through the 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, 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 pool, but is ejected from the system completely.

As the water does not go back into the 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 when you vacuum 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 do I vacuum a pool to waste using 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.

My top three pool cleaning tools to make life easier

Dolphin Nautilus CC Plus Robotic Pool Cleaner – the best time saving product on the market. I have never heard anyone say they regret buying one.

Hayward Poolvac Leaf Canister – very useful when leaves are a problem in your pool

Aquatix Pto Pool Step & Corner Vacuum Head – I use this every time I vacuum my pool. It gets where other vacuum heads can’t.

JP in Fuerteventura

I have had hot tubs for many years and a pool for the last 7 years. I had to learn how to clean it, maintain it and fix it the hard way. Since then I have helped many friends and neighbors with their pools and now I want to share everything I have learned with you.

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