Cleaning algae with a new cartridge filter

Hello. I tried searching the forum for sizing information but not allowed to search.

I have a 12X24 inground concrete pool in Florida. I had an old Posi flow 2 Filter the 50sq. foot model, it broke so i purchased a replacement filter(thinking i was doing something right) and got a Star Clear 50sq foot filter installed.
I am finding that the new filter maybe is too small, maybe the posi flow was a better product, but the problem i have had since i had this installed is that is never really gets the pool clean for long. My latest issue is that Algae has taken over and this filter does not seem to be able to do the job(added algaecide and shock many times, still green). The filter element seems to need cleaning daily. My pressure goes from 24psi to 32psi in about 12 hours and once i hose it out it works again for another 12 hours or so before it climbs up. And obviously when the psi is high it is not flowing much water so the cleaning is diminsihed.

My question: What size filter should i have for a this pool? Sorry for the long explanation but i wanted to explain what i have done. I would have searched but the search is not letting me. Thanks.

I'll let one of the equipment gurus give you a recommendation but it might also be a good idea for you to post a complete set of current water testing results taken with a drops-based kit. A CYA reading is one of the things we will need. If you don't have a good test kit, you should get one. The one we recommend is the Taylor K-2006 or 2006C which you can get through the test kit link in my signature.

Also, tell us what size your pump is when you repost with readings. Then, somebody here can try and help you.

Welcome to the Pool Forum!

By the way -- you can use the Google search in my signature to search. It is much better than the search on the forum software, but you will need to log out to be able to see the search results.

Hi RMA;

The fact that the cartridge is stopping up indicates it is WORKING. Live algae stops up DE filters, and some cartridges: this is NOT a defect.

KILL the algae, and you'll probably solve the problem. And, once it's dead, you'll be glad for a cartridge that will filter out the dead algae, instead of passing it through.

To kill it, you need to know what your CYA (stabilizer) level is. Unfortunately, 'guess-strips' usually aren't accurate enough to help. Do you have a pool store that does a drops (wet) test for stabilizer? If so, have them test your water and tell you what your level is. If you read the Best Guess page (linked in my signature) it will explain what's going on.

However, to really get control of your pool, you need a good test kit. The HTH 6-way kit, available at some Walmarts, does not seem to be available in your area. You can check the link for yourself, however. Otherwise, you'll need a K-2006 -- again, see the link in my signature.

Meanwhile, as a stop gap, if you get a cheap OTO / phenol red drops kit, and check your pool. If the result is anything OTHER than dark yellow, add PLAIN 6% household bleach at the rate of 3 gallons per 10,000 gallons of pool water EACH evening, to maintain a DARK yellow reading. Unless your stabilizer is over 100 ppm, this will probably get things moving in the right direction.

One caution: if you have added a bunch of copper algaecide, you'll need to cut the dose by 2/3, lower the pH to 6.8 - 7.0 and let us know. Killing algae without also staining your pool may be a challenge.

OK. thanks for all the responses. I will have to get a test kit and post results here. I was concerned that maybe for a 10,000 gallon pool that maybe the 50sq foot is too small. I asked that because even when the pool did not have Algae, i was still seeing the pressure go up every other day or so. What is the reccomended size filter for this pool? I would rather know and plan to change the filter is that was the problem - the filter not filtering enough water to keep up. Thanks

Ideally, a cartridge filter should be operated around 0.4 GPM/sft. This is the commercial pool rate . . . which turns out to be the real 'works well' rate for all 3 filter types. This would mean a 20 GPM flow rate for a 50 sft filter. That would give you an 8-hour turnover rate of 20 * 60 * 8 = 9600 gallons, which is OK for your pool.

On the other hand, with a cartridge filter, there's no downside, other than cost, to massively oversizing your filter (you can't do this with DE filters, or especially, with sand filters, which need 15 GPM/sft to backwash properly). So, if you want to reduce filter cleaning frequency, and increase water clarity, you could go with a 100 or even 200 sft filter, and not have any problems, except $$'s of course.

However, for several reasons, if I were you, I'd probably opt to go with a 100sft filter (or else, a 2nd matching 50 ft filter) and have a new spare for each filter, which I would keep in a cleaning solution, so that I could always swap a completely cleaned cartridge for my dirty one.

I second the 100 sq ft filter on a pool your size! (And having a clean spare cart on hand to swap out!)

Thanks. I have noticed that since i have the water quality in better shape(no algae, good Chlorine Levels) that the cleaned filter(6 months old) goes in and starts at 24PSI, then within 8 hours it is up to 30PSI. I take the filter out and wash it with the garden hose and notice that it is not really that bad(dirty). I know that this can't be normal as the pressure coming out of the jets does diminish quite a bit when it is running at 30PSI. When it is at 24PSI the flow is good and strong, but as i said within 8 hours or so, it jumps up to 30PSI and pressure is diminished. I am going to order a replacement filter but i suspect that i just need to get a bigger filter, like the 100sqft one mentioned above and hopefully the time between cleaninigs will be less. My old 50sqft filter used to last 1 to 2 weeks between cleanings, this Hayward although the same size(50sqft) just does not match up. The old one was the Sta Rite 50.