Please help advise on cleaning large filters


Well-known member
Jan 8, 2013
Sydney, Australia

I have a new 150 square foot cartridge filter, this thing is like 3ft tall, I ran it until the water pressure was close to the red and took it out and hosed it off for 30 mins, top to bottom, trying to get the water jet into every crease, that dropped the pressure a bit but nowhere near the brand new level and it quickly went back to close to the red, because I was stuck I bought a second cartridge, problem temporarily solved.

When I ordered the cartridge I also ordered a cleaning spray, I haven't used it yet, the obviously still dirty spare filter has dried and I'm trying to figure out the best way to clean it, I don't have anything right now to completely submerge such a large filter but I could get something if that was necessary.

It's an outdoor, odd shaped pool and so I don't have a cover, it's winter, there are a lot of trees around and quite a bit of construction in my area. Also the pool is over 20 years old and it doesn't have a port for a creepy crawly and the vacuum is broken (it never worked well, it's one of the ones you connect over the skimmer inlet, the whole pool needs an overhaul but I'm scraping by as best I can for now. What I'm saying is the pool bottom is a bit of a nightmare to keep clean, at the moment I'm brushing it and running the pump to filter for an extended amount of time.

Apart from the large filter cleaning suggestions I would also really appreciate any opinions on the best way to keep the whole thing running better. Lately I have been thinking of plumbing a smaller and easier to maintain filter in front of the the large one and also a way to easily vacuum would be amazing, or retrofitting a creepy crawly, the 4WD robot doesn't do too well with the fine stuff on the pool bottom.

Please help you fantastic bunch of humans!

Last edited:


Gold Supporter
LifeTime Supporter
TFP Guide
Oct 25, 2015

I have a pool a little smaller than yours but my cartridge is 200 sq ft. I follow the instructions Allen referenced except I use one of the comb-type attachments. Works like a charm. I remove the filter and stand it on a stool for cleaning, working my way around and vertically from top to bottom. Takes about 20 min. from open to re-started. I've used the current filter for close to 3 years cleaning about every 6 months. Not sure a small filter up front really makes a lot of sense. If you want more time between cleaning a larger filter or parallel unit of the same size would make more sense.

I hope this helps.

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Silver Supporter
Jul 29, 2018
Katy, Texas
I don't think you can get a cartridge filter back to the original flow rate, although the pressure should drop more than just a bit. My guess would be the fine stuff isn't rinsing off. You can try all the TFP recommendations and tricks and also look on YouTube. Maybe buy an inexpensive plastic trash can large enough to hold the filter for soaking. Also you might consider, unless you already have, some "prefilter" option. Skimmer socks, either those sold as such or the far less expensive disposable hair nets, can drastically reduce the quantity of stuff getting to the filter. I use them on each skimmer basket, and every morning I rinse/back wash the sock--and I smile to myself, knowing that all that dirt, leaves, bugs, grass clippings, leaves, flowers, and mystery material would have otherwise been on the main filter cartridges. And it's a lot. Before skimmer socks, the filter cartridges frankly looked pretty disgusting when I cleaned them. After I started using skimmer socks religiously, I found that the filters looked clean even before cleaning, although I could still see a big difference as I hosed them off. I don't soak the filters, but I do a spray of Simple Green before I start the hosing. The other thing is the Maytronics M500 (or M400 or M600) robotic cleaner is nearly a miracle. Three brushes, including one amidships, really whip up the small stuff, silt, dirt, sand and other little things that blow into the pool and sink. The M series comes with two sets of filters, one standard and one fine that looks like the material in the main pool filter, although unlike that one, you can backwash the grime out of it. I have the M500, but frankly the "bells and whistles" that it has over the M400 are not worth the difference in price to me, and the M400 has all the functional capabilities of the other models.
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