Why do I have to backwash my Doughboy Sequel II filter every two minutes?


New member
Jul 9, 2019
Hey guys. First time posting!

Have a question about a pretty annoying problem I've been having. Not sure if it's normal or if somethings wrong.

So, just moved into this house back in December. The last owners informed us that the pool hadn't been opened the previous year. Checked the pool out once Spring was here and found that the winter liner was ripped to pieces. Our pool is 32'x16' and about 20,000 gallons.

The pool looked so bad that you couldn't even see two inches into the water. I finally have it at a really good spot compared to where it was. There is still a good amount of dead algae on the bottom, but the water is crystal clear and all chems are pretty much spot on in terms of balance. My issue though is that every single time we vacuum the dead algae, after about two minutes the filter needs to be thoroughly backwashed and have more DE put in. My wife and I were outside trying to vacuum for about 3 hours yesterday and had to backwash and whatnot probably about 70 times. The filter even needs to be backwashed after a couple hours when we're just letting the pump/filter run on its own. And seeing that we're on city water and have a nasty water bill coming our way due to this, I'm really hoping that the answer is just that something is wrong and we don't have to constantly have the hose running.

We just replaced all 8 of the filter grids as well so I'm kind of at a loss here. Is this normal and should we just keep backwashing this much or is this something else going on here? Thanks in advance!!


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TFP Guide
Hello and Welcome to TFP!

The filter is doing it's job of filtering the water. All that stuff you are sucking up with the vacuum is going into the filter and getting stuck in there. Same issue while in normal filter mode. DE filters are difficult when there is a lot of algae in the water.
Are you using the pressure gauge to determine when the filter needs to be backwashed? We recommend cleaning the filter when the pressure goes up 25% above clean pressures. Do you have a way to vacuum to waste so that the bulk of the stuff stays out of the filter? You would still have the water consumption issue, but not have to clean and recharge the filter every few minutes while vacuuming.

It looks like you've made great progress cleaning the pool. If not already in process, you should be following the SLAM Process to completely get rid of the algae.


Silver Supporter
In The Industry
Aug 15, 2017
Spring Valley, NY
I think the process for back washing a DE filter may not be the same sequence of events as a sand filter. If you don't follow correctly your not completely getting rid of the dirt and are not really getting clean slate at that point. Check YouTube. There you'll find helpful info on DE filter back washing. That maybe why your not getting longer run time between backwash. Also to note, it may be advisable to vacuum to waste rather then through the filter as your trying to rid your pool of this junk. If you need to backwash then let it go to waste and save unnecessary work.