Filter too small?

[MAD_MAX333]

Hello people,

So I have a question. I recently bought a house with a massive old inground pool in it. Size is around 38x20, based on my crude calculations should be around 110000-125000 liters ( 31000+ gallons).
Currently has an old ez-flo 1 speed pump and an old big sand filter.

So yesterday I yanked the old pump and put in a pentair superpump VS for more efficiency and automation of timings.

Question is about the filter. The sand filter is working OK I guess, but when doing cleaning the pressure raises fairly quick from the regular operating psi of 15 to 20 and eventually 25 rapidly. So I got lucky and got a brand new pentair clean-and-clear cc200sq/f cartridge filter. It's brand new in box and I got it for 160 bux! Which is a steal! But when I went to the pool store and they literally and I mean literally laughed at me! Saying it is so small of a pump (it's actually the biggest one of last generation of pumps which is discontinued now)... Saying I need a 460sq/f system which has 4 smaller filters instead of the one big tall one in mine!

Question is, are they just trying to get me to buy a bigger filter from them? Right now with the VS pump my psi in my sand filter is super low (near zero but obviously at least a couple PSIs) so wouldn't the cartridge be fine too? Are they saying it's too small for when I increase the speed for cleaning and the size isn't adequate to push enough water through and I would get psi problems? Or do they mean I would just have to yank the filter out and clean it much more often than a bigger system? Cause I'm OK with cleaning it. Even now I almost have to backwash daily or every other day as is.

I was so excited not to have to do backwashing since my pool has backwash hose buried and brought to the front of my house, so it's a hassle to go there, hook up a backwash hose to the exit, then pack it all up daily!

So what say you guys? Can I get away with the 200sq/f filter? I'll probably be running the pump at 600 or so rpm for about 14 hours a day (haven't done the gpm calculations to figure out the exact flow rates yet) so I can't really see psi issues with the filter...

 

[mas985]

Welcome to the forum!

Question is, are they just trying to get me to buy a bigger filter from them?

Yes. Just a bit of advice:

STOP LISTENING TO POOL STORES

Having said/screamed that, a 200 sq-ft is probably a little on the small side but that just means cleaning it a bit more often.

Even now I almost have to backwash daily or every other day as is.

Even that is way too much for your size pool. You really should be able to get several months out of that filter. More than likely you are fighting an algae bloom. You might want to run an OCLT to check. Since you are new to the forum, you probably don't know what that is so start with these:

Pool School - ABCs of Pool Water Chemistry

Pool School - Perform the Overnight FC Loss Test (OCLT)

Pool School - SLAM - Shock Level And Maintain

 

[kadavis]

That is the great thing about VS pumps, you can adjust the speed to match your needs. You might want to go to the link above Hydraulics 101, depending on the pipe size this can help you set up your pump to deliver the proper gpm through your filter. As a rule of thumb on cartridge filters you don't want to exceed 1/3 gpm per sq. ft. of filter area.

 

[MAD_MAX333]

I am reading and reading on this great forums! thank you for your replies! my goal for today is to figure out all the gpm formulas for my pool. Already ordered a TF100 test kit as was advised by this forum so I can stop relying on the pool store. I went there 4 days in a row....every day they told me I needed something new... literally cost me 200 dollars in chemical between the 4 days and each day results were different... and they said they use Taylor2006 test so I thought they are going to be accurate.

Will read hydraulics and the 3 links posted (had already read the ABCs) and see if it will make my decision easier as to whether or not install the cartridge.