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 and wondering if you can vacuum a pool on backwash is not an unreasonable question.
You can vacuum a pool on backwash, in theory at least, but it would have no benefit. The water would be pumped backwards through the filter, trapping much of the dirt, before passing out through the backwash hose. This dirt 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.
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 the top as it does normally. Then the water passes through the sand or filter medium to the top and out of the waste pipe into the yard, down the drain or wherever your pool expels water to. In doing so it takes any dirt that has been trapped in the top layers of sand and expels it, therefore cleaning the sand.
If you were to vacuum a pool on backwash then all of the dirt you pick up from the pool would mainly get lodged in the bottom layers of the sand and stay there. When you then put the multiport valve back to filter, after you had finished vacuuming, then much of the dirt that had become trapped in the bottom of the sand filter would be pumped back into the pool.
Also, while you were vacuuming on backwash, all of the water would go to the waste pipe so the water level would drop pretty rapidly, just as it would when deliberately vacuuming to waste when a pool is very dirty.
Which settings to use to vacuum a pool
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.
See my post How to vacuum a pool to waste to read more.
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 pool I knew nothing about how to clean and maintain it. I was recommended Swim University’s Pool Care Handbook 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 dong it myself.
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.
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 on 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 on all of the pool forums.