Can You Vacuum a Pool on Backwash?

Getting your first pool, and learning how to clean it yourself, can be quite confusing at first. Learning how to vacuum properly and efficiently is probably the most important thing to learn. So a question many people first have when getting a pool is should I vacuum a pool on backwash or waste or filter?

You can vacuum a pool on backwash, in theory at least, but it would be similar to vacuuming to waste. The water would be pumped backwards through the filter before passing out through the backwash hose. But some dirt would be trapped in the filter and would then end up back in the pool once the pump was back on the filter setting.

I will try and explain why it would not be worthwhile to vacuum on backwash fully so that you can understand better. You can also read my article How do pool vacuums work?

Why shouldn’t you vacuum on backwash?

The reason for this is that when the multiport valve is in the backwash setting the water flows from the pump into the bottom of the sand filter, rather than into the top as it does normally.

When you run the filter on backwash, the water passes through the sand or filter medium from the bottom, picking up trapped debris as it goes, and then expels the water containing the debris out of the waste pipe into the yard, down the drain or wherever your pool expels water to.

If you were to vacuum a pool on backwash then all of the dirt you pick up from the pool would get pushed through the layers of the sand before being expelled out of the system.

Some debris would inevitably get trapped in the bottom of the filter. Then, when you had finished vacuuming and you put the multiport valve back to filter, much of that dirt that had become trapped in the bottom of the sand filter would be pumped back into the pool. This would rather defeat the object of vacuuming the pool in the first place.

So in effect, vacuuming on backwash would have a similar effect to vacuuming on the waste setting of the multiport valve as the water containing the dirt and debris would be expelled from the pool system without going back into the pool. But it would add a pointless step with the water having to pass through the filter medium before being expelled from the system.

See my post Where does backwash water go for more information.

What setting should my pool pump be on to vacuum?

There are only two settings on the multiport valve to use to vacuum a pool and which one you would use largely depends on how dirty the pool is.

Vacuum a pool on filter setting

This is the setting you will use most frequently. You would vacuum on this setting for your routine cleaning when the pool is not very dirty. When you use this setting the dirt is trapped in the sand, or whatever filter medium you have, and clean water returns to the pool via the return jets.

You would often then backwash the filter for a few minutes to clean out this dirt before returning to the filter setting.

Vacuum a pool on waste setting

You would generally only use this setting if the pool is very dirty, perhaps when you do the first clean of the year after the winter or if you had a period of very bad weather when lots of debris ended up in the pool. When to vacuum a pool to waste.

See my full guide How to vacuum a pool to waste to learn how to actually do it.

Can you backwash a pool while vacuuming?

I sometimes have to stop while I am vacuuming my pool on the filter setting (so the water is passing through the sand filter) because the suction begins to reduce. This is due to the sand in the filter becoming clogged which reduces the amount of water that can pass through the sand increasing the back pressure.

You can often tell if this is the problem as the reading on the pressure gauge is likely to be higher than normal because of it.

To restore the suction I switch off the pump and then move the multiport valve to the backwash setting. I then run the pump again for a few minutes to remove the dirt that is blocking the sand and then resume vacuuming once I have put the multiport valve back to the filter setting.

I leave the vacuum hose connected to the skimmer port while I do this so no air gets into the system and I can resume vacuuming straight away after the backwash. Read my full step-by-step backwash guide for further details.

Pool Maintenance Course

When I first bought my house with a swimming pool, I knew nothing about cleaning and maintaining 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.

Further Articles

You may find the following articles useful, particularly if you are a new pool owner. I have tried to answer most of the questions that I had when I first bought my house which came with an in-ground pool with a sand filter system.

How to remove air from a pool vacuum hose

How to bleed air from a pool pump

How often should I vacuum my pool?

Why are there two holes at the bottom of a skimmer?

Best way to get leaves out of pool

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